Download Free Medical ECG grammar part 2 , section B.“Understanding the genesis of ECG changes in common non ischemic heart diseases ”. PowerPoint Presentation

ECG grammar part 2 , section B.“Understanding the genesis of ECG changes in common non ischemic heart diseases ”. PowerPoint Presentation

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Description : ECG changes in common cardiac conditions will be discussed, providing electrophysiological explanation , under the following headings . 1. Genesis of ECG changes in bundle branch block. 2. Understanding the genesis & QRS morphology of premature ventricular beats (PVB) and Ventricular tachycardia (VT). 3. Genesis of ECG changes in right ventricle (RV) pacemaker captured beats. 4. Understanding the genesis of abnormal P waves. 5. Genesis of ECG changes in dextrocardia. 6. Electrophysiological and ECG changes in left and right ventricular hypertrophy .

Tags : LBBB,RBBB,Ventricular tachycardia,Inverted P wave,Situs inversus,Dextrocardia,Ventricular hypertrophy

Published on : Jul 02, 2021 | Views : 1960 | Downloads : 19

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“Understanding the genesis of abnormal ECG ”. ECG grammar part 2. ECG grammar part 2 is uploaded in two sections . Part 2 Section A. Genesis of ECG changes in ischemic heart disease. (This has been already uploaded ). Part 2 Section B. Genesis of ECG changes in common non Ischemic heart diseases. By Asadullah Kundi.
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ECG grammar part 2 , section B. “ Non Ischemic heart diseases”. “Understanding the genesis of ECG changes in common non ischemic heart diseases ”. ECG changes in common cardiac conditions will be discussed, providing electrophysiological explanation , under the following headings . 1. Genesis of ECG changes in bundle branch block. 2. Understanding the genesis & QRS morphology of premature ventricular beats (PVB) and Ventricular tachycardia (VT). 3. Genesis of ECG changes in right ventricle (RV) pacemaker captured beats. 4. Understanding the genesis of abnormal P waves. 5. Genesis of ECG changes in dextrocardia. 6. Electrophysiological and ECG changes in left and right ventricular hypertrophy .
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List of common cardiac conditions (With slide number) discussed in the presentation.
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Copied from https://www.mdnxs.com/topics-2/cardiology/cardiac-physiology/ Brief review of the ventricular conducting system . Note that bundle of His divides into two large branches right and left bundle. Right bundle conducts right ventricle (RV) and left bundle conducts left ventricle ( LV ). Left bundle is larger & further divides into left anterior branch (Fascicle ) & Left posterior branch ( fascicle), Since LV conducting system has two fascicles (bundles) & RV is supplied by Right bundle , thus ventricles have so called trifascicular conducting system. Understanding the genesis of ECG changes in bundle branch block.
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Bundle branch blocks. Understanding the genesis of ECG changes in patient with bundle branch block. Bundle branch block commonly refers to the failure (Blockage ) of conducting electrical impulse down one or both of the bundle branches . Bundle branch blocks are divided into two main groups right bundle branch block (RBBB) & left bundle branch block (LBBB). Blockage of conduction may be in the main right or left bundle or one of the fascicles (branches )of left bundle.
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Copied from https://thoracickey.com/conduction-blocks-and-cardiac-pacing/ Figure A is showing right bundle branch block (RBBB ) , blue color . Left bundle is normal (Green color ) with normal left ventricle (LV ) conduction. Figure B is showing left bundle branch block (LBBB blue color ). Right bundle is normal (Green color) with normal right ventricle (RV ) conduction. RV LV RV LV Bundle branch blocks. Bundle branch blocks (BBB ) are divided into two main types, RBBB & LBBB. A B In the first few slides we will briefly discuss the underlying triggers which generates QRS changes in bundle branch block ( BBB ). Later we will discuss in depth alteration in direction of the vectors of ventricular depolarization & repolarization responsible for the changes in the QRS & T waves. RV LV LV RV
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Copied & Modified from https://www.unm.edu/~lkravitz/EKG/bundlebranch.html What are major ECG ( electrical ) abnormalities in bundle branch block & how are they triggered ? Normally the two ventricles depolarize almost simultaneously .This is why normal QRS width is <100 msec. Major electrical abnormality in bundle branch block is that LV and RV depolarization is out of phase , that is they are not depolarized simultaneously .(Fig. A). Instead the two ventricle depolarize one after the other. What is the impact of out of phase depolarization of the two the ventricles on the ECG ? Hall mark effect of bundle branch block on QRS is wide QRS ( ≥ 120 m sec. ) (Fig. B). Additionally it changes the morphology (shape ) of QRS . This is discussed in the next slide. A B
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Distortion of QRS shape . Another ECG ( electrical ) abnormality in the bundle branch block (BBBB) is distortion of QRST shape. These changes are triggered by changes in the sequence of conduction across right and left bundles. In case of RBBB , LV is first to depolarize followed by right ventricle depolarization.(Fig. A). In LBBB , right ventricle is first to depolarize followed by Left ventricle depolarization.(Fig. B). This alternation in the sequence of conduction results In different QRST shapes in right & left BBBB. Copied from https://www.unm.edu/~lkravitz/EKG/bundlebranch.html A B
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QRS Morphology in Right bundle branch block (RBBB). Understanding the genesis of ECG changes in RBBB. In the next few slides we will address following queries related to ECG changes in RBBB. Why is QRS ≥ 120 m sec in RBBB? Why leads V1 & V2 has rsR pattern & why is second R is taller and wider? Why we have wide S wave in leads V5 & V 6 ? Why are ST & T waves in opposite direction (discordant ) to QRS ?
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Diagrammatic representation of relation of the heart with ECG chest leads V1 & V6. Copied from https://www.teachingmedicine.com/Lesson.aspx LV RV Posterior Orientation of ECG chest leads & heart.
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Fig shows normal four ventricular depolarization (QRS ) vectors (red arrows ) with superimposed chest leads directional map. Modified from https://www.cvphysiology.com/ Cardiovascular Physiology Concepts. Prof. Richard E. Anterior Left lateral. Posterior Correlation of chest leads with vectors of ventricular depolarization .
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Anterior A Copied from http://www.ems12lead.com/wp-content/uploads/sites/42/2014/12/04-Negatives-+-Heart-+-Vector.png Posterior Left lateral. Copied & modified from https://www.cvphysiology.com/Cardiovascular Physiology Concepts. Orientation of LV depolarization vectors generating normal chest leads ECG Fig A shows normal ventricular depolarization (QRS ) vectors with superimposed chest leads location map. QRS vector 2 & 3 are main vectors responsible for depolarization of LV apex & free wall respectively( Fig. A red arrows 2 &3. ). Vector 3 , depolarizing LV free wall , is directed towards the positive pole of V5 & V6 & away from V1. (Fig A red arrow 3). Thus leads V5 &V6 record tall R & lead V1 deep S waves Fig B. Next we will discuss , how QRST vectors in bundle branch block distort the normal chest leads morphology (Shape ) ? B
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QRS Vector 1 In RBBB , left bundle is normal , depolarizing LV with normal conduction sequence (Fig B). Interventricular septum is the first to depolarize (Yellow arrows) as in normal heart (Fig A). This Vector (Vector 1) is directed towards V1/V2 & away from V6.(Fig. A yellow arrows). This will generate r in V1-V2 .It might produce a small Q wave in V6 (fig. C1-C2) Copied from https://www.teachingmedicine.com/Lesson.aspx RV LV Figure B is showing right bundle branch block (RBBB ) , blue color . A Posterior C1 C2 B Copied from https://thoracickey.com/conduction-blocks-and-cardiac-pacing/ RV Copied from https://www.teachingmedicine.com/Lesson.aspx Understanding the genesis of abnormal QRS morphology in RBBB .
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QRS Vector 2 & 3. Following the septal depolarization , LV apex & LV free wall are depolarized by vector 2 & 3 (Yellow arrows) as in normal heart.(Fig. A ) These vectors (Vectors 2 & 3 )are directed towards lead V6 electrode and away from V1/V2 . (Fig A). This will record S wave in leads V1-V2 & R wave in lead V6 .Fig B1 & B2. A Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx B2 B1 Copied from https://www.teachingmedicine.com/Lesson.aspx Understanding the genesis of abnormal QRS morphology in RBBB . (Continued ).
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QRS Vector 4 Finally , as the right bundle is blocked, RV is activated via LV by an additional vector 4 ,blue arrows( Figure A). As this vector is conducted through slow conducting myocardial muscle (Not through conducting fibers) therefore conduction of terminal portion of the QRS is prolonged resulting in wide QRS. Vector is directed towards leads V1/V2 (Figure A).This will produce wide second R waveform in V1/V2 . As the vector is directed away from lead V6 it will generate a wide S wave.(Fig. B2.), because of slow conduction across myocardium. This also explains the wide QRS ≥ 120 m sec. in RBBB. A Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx B1 B2 Copied from https://www.teachingmedicine.com/Lesson.aspx Understanding the genesis of distorted QRS morphology in RBBB .
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Summary of ECG changes in right bundle-branch block(RBBB) compared with normal conduction. In RBBB V1 & V2 has 2nd R wave which is tall & wide ,may be why ? In V6 there is wide terminal S wave , Why ? Why is QRS wide ( ≥ 120 m sec ). Why is ST and T waves in opposite in direction (discordant ) to QRS ? Above first two changes in the terminal portion of QRS are due to late condition of RV by vector 4. Vector 4 is conducted across the myocardium (from LV to RV ) not through fast conducting fibers . This results in wide terminal R in V1-V2 & wide terminal S in V6. This also explains wide QRS (≥ 120 m sec ). Why is ST and T waves in opposite in direction (discordant ) to QRS ? This will be discussed later is section of ECG changes in LBBB.
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QRS Morphology in patient with left bundle branch block (LBBB). Understanding the genesis of abnormal QRS morphology in LBBB. In this section we will address following queries related to ECG changes in LBBB. Why is QRS wide (≥ 120 m sec) in LBBB? Why is R wave peak time >60 m sec in leads V5 -V6 but normal in leads V1, V2, ? Why is ST and T waves in opposite in direction (discordant ) to QRS ?
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Copied from https://thoracickey.com/conduction-blocks-and-cardiac-pacing/ Diagram is showing left bundle branch block (LBBB blue color ). Conduction along the right bundle is normal (Green color) with normal Right ventricle (RV ) conduction. LBBB is either due to structural or functional dysfunction of the left bundle RV LV
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Orientation of the chest leads (V1 & V6 ) & heart. Diagrammatic representation of relation of the heart with anterior chest lead V1 & lateral chest lead V6. LV RV Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx
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QRS Vector 1 (In LBBB) Since the left bundle is blocked , RV will be depolarized first, yellow arrows (Figure A ). Positive ends of these vectors are moving toward VI . Due to thinner RV free wall these vectors will often (but not always) record small r wave in V1.(Fig. B). A Posterior B Copied from https://www.teachingmedicine.com/Lesson.aspx Understanding the genesis of QRS morphology in LBBB.
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QRS Vector 11 (In LBBB) Due to blocked left bundle , LV will be activated from RV ( Fig. A, blue arrows).This vector is conducted slowly because of conduction through myocardium (Instead of fast conducting fibers). Due to prolonged conduction time , QRS waveform will be wide , ≥ 120 m sec. As the vector is directed away from V1-V2 & towards V6 , it will generate wide S wave in lead V1-V2 & wide R wave in V6 . (Fig. B1 & B2). Since leads I & aVL are located close to V6 , QRS pattern similar to V6 may be recorded in these leads too. Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx B 1 B 2 A Understanding the genesis of abnormal QRS morphology in LBBB . (Continued ).
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Intrinsicoid deflection. Intrinsicoid deflection is the time required from start of QRS to peak of R wave. (Blue arrows in fig ) . This is also called the R peak time. In LBBB wide R wave is produced in V6 , by slow conduction therefore the intriscoid deflection is abnormally long (delayed ). The diagnostic criteria for LBBB is an Intrinsicoid deflection > 60 m sec ( Interval between two blue lines). Copied from https://www.teachingmedicine.com/Lesson.aspx Understanding the genesis of abnormal QRS morphology in LBBB.
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As left bundle is blocked, RV depolarization precedes LV. LV is depolarized later from RV through myocardium, which is slow. This results in following first three changes in QRS. 1) QRS duration is prolonged ≥ 120 m sec. 2) Broad notched or slurred R wave in leads V5-V6, lead I, aVL. 3) Intrinsicoid (R peak ) time is > 60 m sec in leads V5 and V6 but Normal in leads V1, V2. 4) ST and T waves are recorded in opposite direction (discordant ) to the QRS. Summary of ECG changes in left bundle-branch block(LBBB) compared with normal conduction. Copied from https://za.pinterest.com/pin/8866530501799003/
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ST -T changes in bundle branch block ? Above is normal ECG (without bundle branch block )?. It has tallest R in lead 11 with biphasic QRS in lead aVL. So main QRS axis is around +60*. T wave is tall in lead 11 & biphasic in lead aVL , the mean T wave axis is around +60*. Thus in normal ECG , T wave has almost same axis as QRS . T and QRS are concordant. Copied from https://www.researchgate.net/profile/Rami_Khouzam/publication/322504203/figure/fig2/AS:591433463525376@1518020134297/Repeat-12-lead-EKG-showing-normal-sinus-rhythm.png
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Understanding ST T changes in bundle branch block. This patient has LBBB with deep S wave in lead 111 & biphasic QRS in lead aVR . Main QRS axis around -60*. T wave is upright in lead 111 & aVF & biphasic (Flat )in aVR. So T wave axis is around +120*. Thus unlike normal (previous ) ECG, QRS axis has left axis deviation & T wave has right axis deviation. Thus in LBBB , QRS & T waves are in opposite direction . They are discordant) ,Why ? Copied from https://i1.wp.com/www.aliem.com/wpcontent/uploads/2010/11/EKG_LBBB.jpg?fit=400%2C258&ssl=1
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Summary of QRS & ST-T, axis in normal versus bundle branch block ( BBB ). In normal ECG QRS & T waves are in same direction concordant. In LBBB , note upright QRS in lead V5 with inverted T waves . QRS & T waves are discordant . Similarly in RBBB QRS is upright in lead V1 with inverted T waves . QRS & T waves are discordant . RBBB LBBB Normal Copied from https://za.pinterest.com/pin/8866530501799003/
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Concept. Understanding the genesis of discordant QRS & T waves in Bundle branch block (Secondary ST-T changes). As discussed , in normal ECG , QRS & T waves have nearly same axis , they are concordant. However in patient with bundle branch block (BBB) QRS & T are directed in opposite direction , they are discordant). Why ?
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+ _ As left bundle is blocked RV is depolarized early & fast. Thus RV repolarization starts earlier than LV . Therefore during early repolarization ,RV surface has positive charge (due to repolarized cells) where as LV has not yet repolarized completely , therefore LV myocardial surface has negative charge. + + _ + _ _ _ Positive electrode ( V6 ) Copied & modified from https://thoracickey.com/conduction-blocks-and-cardiac-pacing/ Diagram is showing left bundle branch block (LBBB blue color ). Vector of repolarization Secondary ST- T changes in left bundle Brach block. Why are ST - T waves directed in opposite direction (discordant ) to QRS in left bundle branch block.? RV LV + Thus negative end of vector of repolarization is directed toward positive electrode of V5 V6 generating inverted ( Discordant ) T waves in LBBB. Same mechanism is true for discordant QRS & T waves in RBBB .
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Terminology of QRS waves in right bundle branch block (RBBB). In RBBB QRS are designated variably as lower case "r" & "s“ (smaller letters ) or upper case (capital ) letters "R" and "S". These simply represent size of the waves. Smaller waveform are represented by lower case & a larger waveform by upper case. For example, rSR' in V1 indicates that second R wave is larger than the first (smaller ) r wave.
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*Summary of diagnostic ECG criteria for complete RBBB in adults. QRS ≥ 120 msec. rsr, rsR, or rSR in leads V1 or V2. S wave of greater duration (Wider > 40 m sec) than R wave in leads I and V6 . Intrinsicoid ( R peak ) time ≥ 50 m sec. in lead V1 but normal in leads V5 and V6 . Exceptions. Patient with anterior wall myocardial infarct first R wave in V1/2 might be missing (because the R wave is replaced by a Q wave). Copied from. https://litfl.com/right-bundle-branch-block-rbbb-ecg-library/ ECG with RBBB. *Reference:. Surawicz B, Childers R, Deal BJ, Gettes LS. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram. J Am Coll Cardiol 2009;53:976–981.
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*Summary of diagnostic ECG criteria for complete LBBB in adults. 1)QRS duration greater than or equal to 120 m sec. 2) Broad notched or slurred R wave in leads I, aVL, V5, and V6 . 3) Absent q waves in leads I, V5, and V6. 4) Intrinsicoid (R peak ) time > 60 m sec in leads V5 and V6 but Normal in leads V1, V2. 5) Secondary ST and T wave changes , directed in opposite to QRS (discordant ) . * Reference:. Surawicz B, Childers R, Deal BJ, Gettes LS. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram. J Am Coll Cardiol 2009;53:976–981. Copied from https://litfl.com/left-bundle-branch-block-lbbb-ecg-library/ ECG with LBBB.
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Premature ventricular beats (*PVB) and Ventricular tachycardia (VT). Concept Understanding QRST morphology in 1. Premature ventricular beats (*PVB) and Ventricular tachycardia (VT). 2. Pace maker captured beats . In literature premature ventricular beats (PVB) is also mentioned as premature ventricular contraction (PVC).
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Copied from https://www.hunterheart.com.au/content/premature-ventricular-contractions-pvcs Diagram above showing focus of premature ventricular beats (PVB) in RV & LV. Purple star represents a PVB focus in the right ventricle (RV) Blue arrows shows “Re entry circuit’ in scar tissue of left ventricle (LV), which generate premature ventricle beats.(PVB ). Conventionally ventricular tachycardia (VT) is defined three or more > three consecutive PVBs with rate > 100 beats/min.
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QRS morphology of premature ventricle beat (PVB) or VT arising from left ventricle (LV) . SA Node Copied and Modified from https://www.teachpe.com/anatomy-physiology/the-heart-conduction-system Vectors of premature ventricular beat (PVB) or VT generated by focus located in the Left ventricle (LV). Blue –red rectangle shows “Re entry circuit’ in scar tissue (PVB focus ) in the left ventricle (LV). RV LV “Re entry circuit
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QRS morphology of premature ventricle beat (PVB) or VT arising from left ventricle (LV) . SA Node Copied and Modified from https://www.teachpe.com/anatomy-physiology/the-heart-conduction-system Action potential from Re entry circuit’ spreads across the LV muscle & is first depolarized (Black arrows). Right ventricle is activated later as wave of depolarization spreads from LV to RV ( red arrows). As the depolarization waves is not conducted by conducting fibers but spreads across the myocardium having slow conduction , it is delayed resulting in broad QRS . More over normally both ventricles are depolarized almost simultaneous. However in this condition LV Is depolarized first & RV is later depolarized later . This sequence of depolarization resemble RBBB in which too, LV is first depolarized. This is why QRS Shape of PVB (PVC) or Ventricular tachycardia, generated in LV resembles RBBB pattern. RV LV “Re entry circuit
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Copied and Modified from https://www.teachpe.com/anatomy-physiology/the-heart-conduction-system QRS morphology of premature ventricle beat (PVB) or VT arising from right ventricle (RV) . Vectors of premature ventricular beat (PVB) or VT generated by focus located in the right ventricle (RV). Blue-Red rectangle shows “Re entry circuit’ in scar tissue (PVB focus )in the right ventricle (RV). SA Node RV LV “Re entry circuit
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Copied and Modified from https://www.teachpe.com/anatomy-physiology/the-heart-conduction-system Action potential from “Re entry circuit first depolarize RV & spread across its muscle (Black arrows). Left ventricle is activated later by wave of depolarization spreading from RV to LV ( red arrows). As the depolarization waves spreads across myocardium , it is delayed resulting in broad QRS . Normally both ventricles are depolarized almost simultaneously. However in this condition RV depolarization precedes LV. This sequence of depolarization resemble LBBB, due to blockage of left bundle RV is first depolarized. Thus the shape of PVB QRS & ventricular tachycardia generated in RV resembles LBBB pattern. SA Node RV LV “Re entry circuit QRS morphology of premature ventricle beat (PVB) or VT arising from right ventricle (RV) .
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Does shape of all premature ventricular beat (PVB ) or VT originating in RV or LV resemble typical LBBB & RBBB respectively ? QRS morphology of PVB or VT originating in LV does resemble RBBB but do not have exactly the same morphology as RBBB. Similarly QRS morphology of PVB or VT originating in RV does resemble LBBB but do not have exactly the same morphology as LBBB. Similarly RV paced beat does resemble LBBB but does not have exactly same morphology as LBBB. Why ? This is discussed in next few slides.
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Copied and Modified from https://www.teachpe.com/anatomy-physiology/the-heart-conduction-system In RBBB , interventricular septum is first to depolarize Yellow arrows followed by LV free wall Fig. A. Figure B shows PVB focus in LV. After depolarization of septum RV is depolarized via myocardial muscle ,Fig A2 Thus both in RBBB and in PVB originating in the LV , LV ventricle depolarization precedes right ventricle depolarization therefore the QRS morphology of such PVB & RBBB have resemblance. However the directions of PVB or VT vectors varies depending on the location of PVB focus (fig. B ) Thus QRS of PVB or VT originating in LV resembles RBBB but does not have exactly the same morphology as RBBB. A B QRS morphology of PVB or VT originating in LV resemble RBBB but why it doesn’t have exactly same morphology as RBBB. ? SA Node RV LV Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx Poster ior A1 A2
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Copied and Modified from https://www.teachpe.com/anatomy-physiology/the-heart-conduction-system SA Node QRS morphology of PVB or VT originating in RV resembles LBBB but why it doesn’t have exactly same morphology as LBBB. In LBBB, as right bundle is normal therefore RV will be depolarized first ( yellow arrows). Figure A1. This is followed by depolarization of LV, blue arrows (Fig. A2) . In patient with PVB or VT focus located in RV will first depolarize RV & then LV (Black & red arrows Fig B ). In this case similar to LBBB , LV conduction is delayed because it is depolarized by RV myocardium. However the direction of the vectors of PVB or VT is variable (Fig. B) Depending on the site of PVB locus. Thus QRS shape of PVB or VT originating in RV resemble LBBB but doesn’t have exactly same morphology A 1 B A 2 RV LV Posterior Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx
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Copied & modified from Edward P. Gerstenfeld , Teresa De Marco Premature Ventricular Contractions, 19 Aug2019https://doi.org/10.1161/CIR ECG below shows premature ventricular beats (PVB.), arrows .They are originating from RV or LV ? These PVBs have LBBB morphology and most probably originating from right ventricle (RV), why ? This is because the PVB vector originating in RV will first depolarize RV. Later, action potential travelling through myocardium (Having slow conduction ) will depolarize LV . Therefore similar to what occurs in LBBB , LV conduction is delayed in a subject with PVB originating in RV & will resemble LBBB.
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Copied & modified from Edward P. Gerstenfeld , Teresa De Marco Premature Ventricular Contractions, 19 Aug2019https://doi.org/10.1161/CIR ECG below shows premature ventricular beats (PVB.), arrows .They are originating from RV or LV ? These PVBs have RBBB morphology and most probably originating from left ventricle (LV) , why ? This is because the PVB vectors originating in LV will first depolarize LV . Later action potential travelling through muscle (with slow conduction ) will depolarize RV . Therefore similar to what occurs in RBBB, RV conduction is delayed in a subject with PVB originating in LV & will resemble RBBB.
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Copied from https://m3.healio.com/~/media/learningsites/learntheheart/assets/8/0/8/5/left_rightbundlevtmorphology.png VT has RBBB morphology most probably originating from left ventricle. This is because the VT with focus in LV will first depolarize LV . Later action potential travelling through muscle (with slow conduction ) will depolarize RV . Therefore similar to what occurs in RBBB, RV conduction is delayed in a subject with VT originating in LV & will thus resemble RBBB pattern. Following is ECG of a patient with ventricular tachycardia .QRS morphology of this resembles LBBB or RBBB ? Ventricular tachycardia with RBBB type morphology.
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Copied from https://m3.healio.com/~/media/learningsites/learntheheart/assets/8/0/8/5/left_rightbundlevtmorphology.png VT that has a LBBB morphology most probably originates somewhere from the right ventricle. This is because the vectors originating with VT focus in RV will first depolarize RV. Later action potential travelling through muscle (with slow conduction ) will depolarize LV . Therefore similar to what occurs in LBBB , LV conduction is delayed in a subject with VT focus in RV & it resemble LBBB. Following is ECG of a patient with ventricular tachycardia .QRS morphology of this resembles LBBB or RBBB ?
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Copied and modified from https://www.ecgmedicaltraining.com/wp-content/uploads/2015/07/pacemaker-syndrome-wm.jpg ECG below is recorded in a patient with right ventricular pacing .(Pacemaker lead is placed in RV). The paced beats have QRS morphology resembling LBBB. Why LBBB pattern ? Pacemaker lead in RV will obviously first depolarize RV. Later action potential travelling through muscle (with slow conduction ) will depolarize LV . Therefore similar to what occurs in LBBB , LV conduction is delayed & RV paced beat resembles LBBB. Pacing spikes Pacing spikes
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P wave morphology (shape ) in atrial enlargement . In this section we will discuss following aspects of atrial enlargement. 1. Genesis of morphological changes in the left & right atrial enlargement. 2. We will also discuss the explanation of following frequently asked queries regarding atrial enlargement. a. Why is P wave tall & not wide in RA enlargement ( RAE )? b. Why is P wave wide & not tall in LA enlargement ( LAE )? 3. We will also discuss the electrographic enlargement of LA with normal left atrial size.(False positive ECG).
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Atrial depolarization starts in the SA node , (RA) is first to depolarize followed by very short time lag LA is depolarized. Thus Initial portion of P wave mostly represents RA & later portion of P wave presents LA conduction. LA enlarge is commonly directed posteriorly &inferiorly. As left atrium increases in size conduction across it is delayed. Concepts. P wave morphology in patients with Left atrial (LA) enlargement. LA RA Fig. shows anatomical relation of RA , anterior & LA posterior, with the positive electrode of V1 & V6. Note the posterior directed LA enlargement (Yellow outline ). Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx Posterior.
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RA depolarization vector is directed towards positive electrode of V1 ( Short blue arrows) fig A. As RA is first to depolarize & vector is directed anteriorly, the initial component of P wave is upright .Fig C1 Later LA is depolarized the vector is directed posteriorly away from V1 (long blue arrows) ( fig .B ). Thus in LA enlargement , P wave has biphasic shape. Initial portion of RA conduction (red arrow Fig C 2)is upright & terminal portion generated by LA is inverted , small blue arrow. (Fig C2) Wide & deep P in V1 is to due to delayed conduction in large LA which is directed away from V1.Fig. B &C2. Orientation of vector of atrial depolarization (P wave ) LA enlargement (LAE) in lead V1. RA LA B A C 1 C 2 Posterior Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx
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Copied From https://www.cmcecg.com/sinus.html In the frontal plan mean axis of atrial vector is directed inferior & left, around 40 * ( Fig. A). Large LA delays conduction & prolongs depolarization. Thus wide upright P wave is generated in the limb leads particularly lead 11 (As P wave vector is adjacent to lead 2.) Left atrium is located posteriorly . Thus posteriorly directed LA depolarization vector is directed away form Lead V1.(Fig B ). Large LA delays conduction prolongs depolarization. This generates deep (inverted ) & wide terminal component of P wave. In LA enlargement why P is wave wide in limb lead 11 & terminally inverted & wide in lead V1? LA enlargement viewed in frontal plane, limb leads. LA enlargement viewed in cross section plane, chest leads. Copied From https://www.cmcecg.com/sinus.html A B
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Note that mean P wave axis ( +40* to +50*) is close to lead 11 (+ 60*) therefore LA enlargement is distinctly recorded in lead 11.(Fig. A ). In atrial enlargement, P wave measured in lead II is recorded as two separate waves. RA & LA components.(Fig B1). In the diagram B 2, there is an extra blue and red fuzzy lines to show the two different atrial waves. The first component is due to depolarization of RA & 2nd due to LA .The two waves overlap. It creates an M shaped P wave in lead II. This is also called camel hump or bifid P wave . Morphology of P wave with LA enlargement in Lead 11. B1 B2 Copied & modified from https://www.teachingmedicine.com/Lesson.aspx A Copied From https://www.cmcecg.com/sinus.html
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Copied from https://ecg.utah.edu/lesson/7 Summary of Diagnostic Criteria for Left atrial enlargement ( LAE). M shaped wide (> 120 m sec.) P wave in lead II. Biphasic P wave in lead V1 (initially upward ( RA component ) ,terminal portion downward (LA component). Terminal portion of V1 is wide (≥ 40 m sec.) and deep (≥ 1 mm or 0.1 mv).
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Concepts of right atrium (RA ) enlargement . Why is P wave tall in limb (frontal ) leads (Lead 11 & aVF )? Why is P wave tall in chest (cross sectional) leads ( V1) ?
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Large RA generate high magnitude depolarization vector directed around +80*(Fig A & B blue arrows). As this vector is parallel & close to lead 11 & aVF it will generate tall P wave in these leads.(Fig C). P wave height > 2.5 mm (0.25 mv ) in lead II is diagnostic of right atrium enlargement ( RAE ). P wave morphology in limb leads in right atrial enlargement (RAE). Copied from https://www.teachingmedicine.com/media/lessons/images/ECG%20grow%20sequence-2.png Copied from https://elentra.healthsci.queensu.ca/assets/modules/ECG/right_atrial_enlargement.html Copied & modified From https://www.cmcecg.com/sinus.html A B C
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Fig. shows anatomical relation of lead V1 with RA (located anterior) & LA posterior. Enlarged RA will create a strong vector directed anteriorly towards V1 as seen in the fig. This will result in a taller P wave in V1 . P wave taller than 1.5 mm (0 .15 mv) in lead V1 is suggestive of RA enlargement. Morphology of P wave in lead V1 in patient with RA enlargement. V1 Posterior Anterior RA LA Copied from https://www.teachingmedicine.com/Lesson.aspx
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Fig. shows anatomical relation of lead V1 with RA (located anterior) & LA posterior. Rarely if the RA gets very large, it can grow toward the left (Yellow outlines in the fig.) In this rare condition the terminal RA depolarization will be directed away from V1 generating inverted P waveform. This resembles left atrial enlargement. Summary of diagnostic criteria for right atrium enlargement ( RAE ) in V1. P wave taller than 1.5 mm in lead V1 with P wave duration < 120 msec. P wave morphology in lead V1 in patient with very large (Huge ) RA enlargement . Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx
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RA enlargement viewed in (Frontal ) limb leads RA enlargement viewed in (Cross section ) chest lead V1 Summary of the genesis of tall P waves in the limb leads 11, aVF& in the chest lead V1 . In the frontal plan RA vector is directed inferior & left , at an angle of around +80*. It is directed close to the positive electrode of lead 11 and aVF. This generate tall P wave in lead 11 and aVF. As RA is located anterior vector is directed anterior toward positive electrode of lead V1 . Enlarged RA will generate strong electrical signals resulting in tall P wave in V1 Copied From https://www.cmcecg.com/sinus.html
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Copied from https://ecg.utah.edu/lesson/7 Diagnostic ECG Criteria for right atrial enlargement ( LAE). Tall P waves in limb lead 11, aVF & chest lead V1 (Arrows ).
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P wave morphology (shape ) in atrial enlargement . The most interesting aspect of P wave morphology (Shape )in enlarged atria is to understand the concept of 1. Why is P wave tall & not wide in RA enlargement ( RAE )? 2. Why is P wave wide & not tall in LA enlargement ( LAE )?
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Why is P wave tall & not wide in RA enlargement ? Why is P wave wide & not tall in LA enlargement ? Enlargement of atria is associated with two electrophysiological changes . 1.Increase in voltage (height ) of P wave due to increased magnitude of electrical signals (action potential) . 2. Increase in width of P wave due to prolonged conduction of electrical signals (action potential) . However in RA enlargement (RAE ) , P waves recorded in ECG is tall but not wide ? Similarly in LA enlargement (LAE ) , P wave recorded in ECG is wide but not tall ? In the next few slides we will discuss the explanation for this apparent contradiction.
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To understand this we need to review the components of P wave. P wave represents atrial depolarization & has two components. Components of RA & LA depolarization. SA node depolarizes RA , so the initial part of P wave represents RA depolarization. (Figure ) Later LA begins to depolarize . It is important to note that RA depolarization is completes approximately at peak of LA depolarization. Therefore LA ,RA depolarization curves overlaps each other. (Figure ) Copied from https://drsvenkatesan.com/2009/09/20/why-p-wave-becomes-tall-in-ra-enlargement-and-wide-with-la-enlargement/ ... Fig. Normal P wave components of RA & LA, showing short time lag between two waves. RA, LA depolarization curve overlap each other. Why is P wave tall & not wide in RA enlargement ? Why is P wave wide & not tall in LA enlargement ?
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LA is a midline posterior chamber , lying close to the spine.(Fig. A). LA depolarization vector is directed posterioateral ( fig A , blue arrows ). As the vector is directed away from V1 Thus wide , deep inverted P is recorded in V1.(Fig. A & B red color ). Additionally due to late & delayed LA depolarization , wide P wave is recorded in the limb leads. (Fig B). RA LA A A Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx Copied from https://drsvenkatesan.com/2009/09/20/why-p-wave-becomes-tall-in-ra-enlargement-and-wide-with-la-enlargement/ ... Why ECG record wide P wave in LA enlargement (LAE) ? B Fig. Showing depolarization components of P wave in large LA. LA component stretches laterally beyond normal limits (Dotted curve Posterior extension of LA wave Is recorded in chest lead V1.
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LA is a midline posterior chamber , lying close to spine , far away from the chest wall (Fig. A). Even when LA enlarges it doesn’t extends close to chest wall . Therefore strong signals of large LA are not well picked up by the ECG leads in frontal plan limb ( Lead 11). Thus in LA enlargement high voltage (Tall ) P wave is not recorded in front plan limb leads (lead 11) A A Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx Copied from https://drsvenkatesan.com/2009/09/20/why-p-wave-becomes-tall-in-ra-enlargement-and-wide-with-la-enlargement/ ... Why doesn't ECG record high voltage (tall ) P wave in LA enlargement (LAE)? Fig. B Showing components of P wave of large LA. LA component stretches laterally not superiorly (Dotted curve ) thus high voltage ( tall ) P wave is not recorded in ECG. B RA LA
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Copied & modified From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif Limb leads (Frontal plane leads) These explore electrical activity along two axis . X axis (Right left ) & Y (Superior -inferior) These leads best record the electrical signals (Vector ) moving along X & Y axis . Superior Inferior Posterior Copied From https://ecgwaves.com/ecg-topic/ekg-ecg-leads-electrodes-systems-limb-chest-precordial/ Chest leads.(Cross sectional plane leads ) They explore the electrical activity along Z axis (Anterior – posterior ) & X axis (Right Left ). These leads are best for recording vectors moving in Z and X axis . High magnitude vectors of LA enlargement is not recoded in limb lead (11) but are recorded in chest lead (V1). Why ? To understand this we need to review the orientation of the electrical signals recorded by these leads . Anterior
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High magnitude vectors of LA enlargement is not recoded in limb lead (11) but are recorded in chest lead (V1) Why ? Another important aspect of LA enlargement & P wave changes is that high magnitude electrical signals are generated but are not picked up by frontal plane limb lead (Lead 11). Therefore P wave in lead doesn’t have high amplitude However these high magnitude signals are picked up by chest lead ( cross sectional lead ) V1 & recorded as P wave with deep & inverted terminal portion . This inconsistency is due to the fact that limb & chest lead records electrical activity in different planes. Electrical activity in frontal plane ( X axis & Y axis ) is recorded by the Limb leads. Electrical activity of the cross sectional or horizontal plane (Z axis & X axis ) is recorded by chest leads . LA is posterior most chamber & is far away from the anterior chest wall. Thus the anteriorly directed LA signals (In Z axis ) is not well picked up by lead 11 which mainly records electrical activity in X & Y axis. Where as chest leads records electrical activity in Z & X axis . Therefore strong signal (Vectors ) of large LA directed posteriorly in Z axis are well picked up by V1 & recorded as deep terminal portion of P wave. Where as these signals in Z axis are not well picked up in lead 11.
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Fig. shows anatomical relation of RA , anterior & LA posterior, with anteriorly placed lead V1.. The main reason for high voltage (tall ) P wave in RAE is due to the proximity of RA to the chest wall . RA voltage increase is easily picked up by chest & limb leads , recording tall P waves in RAE.(Fig. B ). RA LA B A Posterior Copied from https://www.teachingmedicine.com/Lesson.aspx Why ECG record high voltage ( tall ) P wave in right atrial enlargement (RAE) ? Copied from https://drsvenkatesan.com/2009/09/20/why-p-wave-becomes-tall-in-ra-enlargement-and-wide-with-la-enlargement/ ... Fig. Showing components of P wave in patient with REA. High voltage depolarization RA component of P is due to the anatomical proximity of RA to the chest wall . Thus high voltage (tall ) P wave is recorded in ECG (Dotted curve ). B
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As discussed in previous slides RA depolarization precedes LA depolarization. RA & LA depolarization waves overlaps each other. Fig. If the RA conduction is prolonged in RAE ,RAE Curve of P Wave will still fall within the LA curve.( Fig ). Thus terminal portion of the RA curve is not recorded in the ECG & P wave is not widened in RAE. Copied from https://drsvenkatesan.com/2009/09/20/why-p-wave-becomes-tall-in-ra-enlargement-and-wide-with-la-enlargement/ ... Fig. Showing the overlapping of P wave depolarization curves of RA & LA in RAE. Note that RA conduction is prolonged but still the REA curve falls over LA curve. (Dotted curve ). Thus wide P wave is not recorded in patient with REA. Why doesn't ECG record wide P wave in RA enlargement (RAE)?
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Copied & modified from https://dundeemedstudentnotes.files.wordpress.com/2012/06/picture1.png Summary of P wave morphology in normal and atrial enlargement. Normal RA enlargement LA enlargement Lead Features of left atrial enlargement. Lead I1 or I: P wave is wide (>2.5 mm) and bifid ( *Specific, not sensitive) . V1: Terminal Negativity > 1mm ( *Sensitive, not specific) Features of right atrial enlargement. II, III, aVF: Tall and peaked P (2.5mm or 1/3 QRS height in 2 of 3 (Sensitive, not specific). FeaturesV1: initial up going g component > 1mm (Specific, not sensitive). ECG has limited specificity for RAE. *Sensitive test has few false negative. *Specific test has few false positive.
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Copied & modified from https://drsvenkatesan.com/2009/09/20/why-p-wave-becomes-tall-in-ra-enlargement-and-wide-with-la-enlargement/ ... What is possible cause of LA enlargement in ECG ? This is an ECG of a 42 year old man .His ECG was reported to have left atrial enlargement &was referred for echocardiography . His echo was normal . LA measured 2.5 X 3.1 cm . This is example of false positive ECG. ECG changes of LA enlargement with normal LA size. What is cause ? Inter atrial conduction block.
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Differential diagnosis of LA enlargement recorded in ECG. P wave morphology suggestive of LA enlargement (LAE) in ECG may be present in the following conditions. Atrial enlargement, atrial dilatation, atrial hypertrophy, intra atrial & inter atrial block ? The P wave morphology has no specificity to identify these various entities. Intra or inter atrial conduction delay is found in initial stages of all of the above conditions. Thus a wide P wave can occur due to LAE . It can be due to conduction delay without LA enlargement (False positive ECG ). Thus one can not confirm LAE without echocardiogram . Copied from https://drsvenkatesan.com/2009/09/20/why-p-wave-becomes-tall-in-ra-enlargement-and-wide-with-la-enlargement/ ...
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ECG with LA enlargement with normal LA dimension (False positive )is not uncommon. The P wave abnormality in the above patient is due to Inter atrial block (IAB ) . This widens the p wave . Copied and modified from
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Pretest. Instructions. Don’t guess if you don’t know , select “ I don’t know”. Don't worry about your pretest score. You are expected to achieve ≥ 65 % score in post test if you read the article carefully. Q 1.This ECG was recorded from an asymptomatic 30 years male. Select the correct option. a. ECG is Suggestive of dextrocardia. b. ECG is suggestive of upper Limb lead reversal. c. Patient has situs inversus. d. I don't know. African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139
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Copied and modified from https://ecg-educator.blogspot.com/2016/08/dextrocardia_43.html Q 2. This ECG was recorded from an asymptomatic 10 years boy. Select the correct option. a. He has dextrocardia. b. ECG is suggestive of limb lead reversal. c. He has isolated situs inversus. d. I don't know.
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Q3 .This ECG was recorded in a 50 years diabetic patient with chest discomfort. Select the correct option. a. Patient has Junctional rhythm . b. ECG is suggestive of Limb lead reversal. c. He has situs inversus . d. I don't know. Key is at the end of presentation. Copied from https://ecgguru.com/ecg/ Donated by Michael Francis and Chris Burden..
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Copied from https://www.facebook.com/MedicalMcq.page/photos/dextrocardia-ecg-characteristic-ecg-findings/1292071200826145/ Q 4.This is ECG of a 30 years asymptomatic man who had applied for technician job. Select the correct option. a. He has dextrocardia. b. ECG is suggestive of limb lead reversal. c. He has isolated situs inversus. d. I don't know.
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Understanding the genesis of abnormally inverted P waves.
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Inverted P wave. Normally P waves are inverted in lead aVR. It may be inverted in lead V1 & rarely in lead 111. When P waves are inverted in leads 1, 11, 111 and aVF they are called abnormally inverted P. This is commonly associated with upright P wave in lead aVR.
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Copied from https://www.teachingmedicine.com/Lesson.aspx?l_id=78 In normal person, why are P wave upright in most of the limb leads except aVR ? We have already discussed this in in ECG grammar part 1. Briefly P wave generated in the SA node (Fig A), travels inferiorly towards left , directed around an angle of +50* to +70 *. Fig A(Blue arrow) At this angle the P wave vector is directed towards the positive ends of lead 1, 11. aVF & 111, (Fig .B ) therefore P wave is upright in these leads. (Fig C) However P wave vector at an angle +50* to +70* is directed towards negative end of aVR.Thus P wave in aVR is negative. Copied & mofirirf From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif A B C
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Inverted P waves. In certain conditions P waves are inverted in lead 1, 11, 111, aVF and upright in lead aVR. These are referred to as an abnormally inverted P waves. We will discuss in detail genesis of inverted P waves in following conditions A. Inverted P waves in Junctional rhythm (Also called AV nodal rhythm ). B. Inverted P & QRS waves associated with congenital heart diseases. 1. Situs inversus. 2 . Dextrocardia. C. Inverted P & QRS waves due to malposition of ECG leads. Note that in Junctional rhythm only P wave are inverted, QRS is unchanged (Unless P wave falls on QRS).
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Genesis of P wave in Junctional rhythm (AV node rhythm). Junctional rhythm originates in the AV node (Instead of SA node ). AV node is located in the right atrium, at the junction of atrium and ventricle. Therefore impulse generating in the AV node is called Junctional rhythm . Normally frequency of AV node rhythm is slower than the SA node .
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P wave generated in AV node , Junctional rhythm . If rhythm is generated in AV node or near by, inverted P waves are recorded in leads 1, 11,111,aVF.(Fig C). This is because mean vector of P is directed superiorly at an angle of -100* to – 120* (Fig A). directed towards the negative pole of lead 1, 11, aVF therefore these lead generate negative P waves.(Fig B & C ). However as the mean vector is moving towards positive end of lead aVR ,P wave is upright in lead aVR . If P wave is generated in lower part of atrium , P wave morphology is almost same as that arising from AV node because the direction of P wave vector in such cases is almost same (directed superiorly). Copied from https://www.teachingmedicine.com/Lesson.aspx?l_id=78 Copied From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif A B Fig. showing atrioventricular junction & direction of vectors generated at AV node. Copied & modified from https://www.ecgguru.com/ecg/pediatric-ecg-junctional-rhythm C
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AV node. Middle AV zone. Upper AV zone. Lower AV zone. AV node is arbitrary divided into three zones 1.Upper zone .It lies at the junction of the atrium & AV node. 2.Middle zone. It the central part of AV node. 3.Lower AV .It is the junction of AV node with ventricle. Depending on the site of origin of Junctional beat three types of Junctional rhythms can be recorded in the ECG. 1. Junctional rhythm arising from upper zone. 2. Junctional rhythm arising from middle zone . 3. Junctional rhythm arising from lower zone . Copied & modified from http://pediatricepsociety.org/Images/heart_1.aspx
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Rhythm located in Upper zone of AV node. Copied & modified from https://www.teachingmedicine.com/Lesson.aspx?l_id=67 Genesis of P wave generated in upper zone of the AV node. As the focus of generated P wave is close to atrium, retrograde conduction will depolarize atria before the ventricles. Thus P wave recorded will precede QRS. The mean P wave axis is -100* to -120* (short black arrow ). This will record inverted P in lead 1,11, aVF & upright in aVR. Antegrade conduction from upper zone AV node towards ventricle is delayed due to slow conduction across AV node . QRS will follow P wave but PR interval is short ( Fig ECG strip). This short PR is because as compared to normal sinus rhythm , in AV nodal rhythm ,ventricle is depolarized earlier as focus is located in AV node (close to ventricle as compared to SA node.) P waves are inverted ,precedes QRS with short PR interval. Copied & modified from http://pediatricepsociety.org/Images/heart_1.aspx AV node
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Rhythm located in Mid zone of AV node. Copied & modified from https://www.teachingmedicine.com/Lesson.aspx?l_id=67 Genesis of P wave generated in mid zone of AV node. In this case electrical impulses arising from mid AV node is conducted retrograde (upwards) into atria & antegrade (downward) into ventricle almost at the same time. Thus P wave and QRS waves are recorded simultaneously. As QRS has increased width , P wave is concealed ( hidden) in it & therefore it is not visible the ECG. Junctional rhythm with absent P waves. ( Concealed in QRS ). Copied & modified from http://pediatricepsociety.org/Images/heart_1.aspx
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Rhythm located in Lower zone of AV node. Copied & modified from https://www.teachingmedicine.com/Lesson.aspx?l_id=67 Genesis of P wave generated in lower AV nodal zone. As the rhythm is in lower zone of AV node, close to ventricle , it is depolarized first .(Blue arrow). Upward electrical conduction towards atria is delayed because it has to cross AV node tissue which has slow conduction.(White curved arrow ). Therefore P waves follows QRS ( ECG, red arrows). Moreover the mean axis of retrograde atrial conduction is around -100* to -120* ( White arrow in Fig). Shape of inverted P is altered as they fall on ST segments . Junctional rhythm in lower zone of AV node . P waves are inverted & follow QRS. Copied & modified from http://pediatricepsociety.org/Images/heart_1.aspx
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B . Abnormally Inverted P & QRS waves in patient with congenital heart diseases. In certain rare congenital heart diseases patient may have abnormally inverted P waves . These condition , unlike Junctional rhythm , is commonly associated with inverted QRS in leads with normally upright QRS. To understand the genesis of inverted P & QRS in patient with congenital heart diseases we need to understand Visceral and atrial Situs.
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What is visceral & atrial Situs. Situs,(Latin) means position or location. In case of organs it refers to position of the viscera in the body. Situs is classified into two types. 1.Situs Solitus 2.Situs inversus 1. Situs Solitus. Situs solitus means usual or normal position of major thoracoabdominal viscera. This is associated with normal visceral situs . 2.Situs inversus . Situs inversus is a congenital condition in which the major thoracoabdominal viscera are reversed . left right across the midline (along X axis ).They lie on opposite , left to right position across the midline.
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Illustration of visceral & atrial Situs. 1.Situs Solitus. In this major thoracoabdominal viscera lie in normal left to right position across the midline. Normally *morphological right atrium (RA ), right sided (Trilobed ) lung, Liver, inferior vena cava ,all are on the right side of the midline. Similarly the morphological left atrium (LA ) ,left sided ( bilobed )lung, Stomach, and descending abdominal Aorta all are located on the left side of the midline. It is important to note that the position of Atrium almost always go along with the viscera not ventricles. Thus in situs solitus morphological RA is on right & LA is on the left side of the midline(Figure). Thus position of atria (Atrial situs ) follow the visceral situs. Other cardiac chambers don’t strictly follow the visceral situs. Copied & modified from https://radiologykey.com/visceral-situs-heart-position-and-aortic-arch-position/ RA LA *Morphology means naked eye appearance (structure).
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Situs inversus (Inverted position of viscera ). In this condition there is left to right reversal of major thoracoabdominal viscera & placed on the opposite side across the midline . In situs inversus right sided ( trilobed ) lung Liver, inferior vena cava are shifted on the left side of midline. Left sided ( bilobed )lung, Stomach, and descending aorta, all are placed on the right side of the body. Thus morphological right atrium is placed on the left side & left atrium shifted to the right side of midline. *In the fig. A note that situs inversus is only associated with atrial inversion , without ventricular inversion. Copied & modified from http://blog.clinicalmonster.com/2015/08/06/morning-report-862015/ Copied & modified from http://blog.clinicalmonster.com/2015/08/06/morning-report-862015/ Situs inversus Levocardia means Apex of heart on left side (normal ) RV LV A B
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Copied & modified from http://blog.clinicalmonster.com/2015/08/06/morning-report-862015/ Fig . A shows situs inversus without ventricular inversion normal long axis , left sided LV apex(Levocardia) Note that in Fig B, situs inversus is associated with dextrocardia as well as atrial & ventricular inversion. It is important to remember that atrial inversion is strongly associated with situs inversus. However ventricular inversion or dextrocardia may or may not be present in situs inversus. What is clinical importance of establishing Situs ? Two D echo imaging can readily establish visceral situs & thus help establishing atrial situs . B A Association of other congenital cardiac anomalies with situs inversus. RV LV Situs inversus with atrial inversion with Levocardia.
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Copied and modified. from https://www.slideshare.net/mallesh2006?utm_campaign=profiletracking&utm_medium=sssite&utm_source=ssslideview Situs solitus With this brief background knowledge about the atrial & visceral situs it is now easy to understand the genesis of inverted P waves in patient with some congenital heart diseases. LA RA A Copied From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif Fig. A shows normal position of the atria ( situs solitus ) with morphological RA on right of morphological LA. P wave vector , generated in the SA node travels inferiorly & left (Fig. A black arrow) with mean axis around +60* It is directed towards the positive terminal of lead 1, 11. aVF & 111 & negative terminal of lead aVR. .(Fig. B) Thus it will generate upright P waves in leads 1, 11, aVF & inverted in lead aVR. (Fig C). B C http://www.ems12lead.com/wp-content/uploads/sites/42/2014/12/04-Negatives-+-Heart-+-Vector.png
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Copied and modified. from https://www.slideshare.net/mallesh2006?utm_campaign=profiletracking&utm_medium=sssite&utm_source=ssslideview Situs solitus Situs inversus. LA RA LA RA A B Copied From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif Fig. A shows normal position of the atria ( situs solitus ) with morphological RA on right of morphological LA. Fig. B shows atrial reversal, morphological right atrium located to the left of left atrium (Situs inversus ). Mean axis of P wave vector generated from morphological left sided right atrium, is directed inferiorly & right , around an angle of +140* to + 160*, right axis deviation.(Fig B black arrow). It is directed towards positive end of lead 111 & aVF but is closer to negative terminal of lead 1.(Fig C). Thus in situs inversus P waves are upright in lead 111& aVF but negative in lead 1. C P wave morphology in patient with situs inversus.
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A 1 A 2 Copied & modified from https://www.slideshare.net/mallesh2006?utm_campaign=profiletracking&utm_medium=sssite&utm_source=ssslideview Copied & modified from https://thoracickey.com/wp-content/uploads/2016/09/chapter-36-Fig.36.10.jpg Summary. Understanding the direction of mean P wave axis & shape of P wave in situs solitus & situs inversus. P wave morphology in Situs solitus P wave morphology In Situs inversus. RA B LA LA RA C Fig A1 is showing direction of mean P wave axis + 60 in situs solitus. Fig B is showing P wave morphology (Shape) in situs solitus with Upright P waves in leads 1, aVF . Fig A 2 is showing direction of mean P wave axis +150 in situs inversus Fig C is showing P wave morphology (Shape) in situs inversus with inverted P wave in lead 1 & upright in lead aVF.
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Ayman S. Al-Khadra. Circulation. Mirror-Image Dextrocardia With Situs Inversus, Volume: 91, Issue: 5, Pages: 1602-1603, DOI: (10.1161/01.CIR.91.5.1602) Copyright © 1995 by American Heart Association Note that P wave are upright in 11, 111,aVF but inverted in lead 1. Mean P wave has right axis > +110*. This is suggestive of either atrial reversal or Left atrial rhythm.(Both are rare) However as patient has situs inversus (visceral reversal) atrial reversal is confirmed as it is invariably associated with situs inversus. Non progressive R in chest leads favor's dextrocardia & excludes limbs lead reversal. As discussed situs inversus may be present with or without dextrocardia. ECG of patient with Situs Inversus & dextrocardia.
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Abnormally inverted P waves due to limbs lead reversal. Introductory note (Already discussed in detail in ECG grammar part 1.) The terms electrode and lead are often used interchangeably. However, electrodes are attached to the skin while leads are the vectors between the electrodes. For instance , lead 1 is an electrical vector representing voltage between the right and left arm electrodes. Four limb electrodes generates six ECG limbs leads (leads I, II, III, aVR, aVL, and aVF). Misplacements of electrodes will obviously change the ECG wave form . Right leg electrode is the grounding electrode & does share in generating ECG wave form. However, it is important to note that if it is misplaced with arm electrodes, flat lines may be recorded in bipolar limb leads
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Abnormally inverted P waves due to limbs lead reversal . There are many possible errors in lead placement, which can alter the ECG recording. Most common error is upper limb lead reversal ( left & right arms lead reversal) . We will discuss ECG changes recorded in this type of lead misplacement ? We will also discuss in detail , why /how these changes occur ? First we will review the connections & directions of normal limb leads already discussed in ECG grammar part 1.
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The above illustration shows Leads I, II, and III, placement & the electrical charges of their electrodes. They are summarized as follows: Lead I: Right arm-negative, Left arm-positive (Positive end is at +zero degree ). Records electrical differences (voltage )between left and right arm electrodes. Lead II: Right arm-negative, Left leg-positive( Positive end is at +60 degree). Records electrical difference (voltage ) between right arm & left leg electrodes. Lead III: Left arm-negative, Left leg-positive ( Positive end is at +120 degree). Records electrical differences (voltage ) between left arm & left leg electrode. Right leg doesn't contribute in ECG wave form recordings & is considered as a grounding lead that helps minimize ECG artifacts. Lead I Lead II Lead III Connections & directions of normal bipolar limb leads . Copied and modifed From https://www.nurseslearning.com/courses/nrp/nrp1619/Section%205/index.htm Chapter V The 12-Lead EKG.
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Normally placed Augmented unipolar limb leads connections. aVL , the positive electrode is on the left shoulder at – 30*. aVL records an average voltage between RA – LL. aVR , the positive electrode is on the right shoulder at -150 *. *aVR records an average voltage between LA – LL. aVF, the positive electrode is on the left foot at +90*. Lead aVF records an average voltage between RA- LA. Note that the positive electrodes of aVR and aVL are located in the negative electric zone. Copied and modifed From https://www.nurseslearning.com/courses/nrp/nrp1619/Section%205/index.htm Chapter V The 12-Lead EKG. Negative electrical zone of ECG. Positive electrical zone of ECG. *RA=Right arm, LA = left arm , RL = Right leg , LL = left leg.
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Copied & modified from https://litfl.com/ecg-limb-lead-reversal-ecg-library/. Dr Ed Burns. Figure B shows the change in the directions of the leads due to left & right arm lead reversal. With reversal of the LA and RA electrodes, all limb leads replace each other due to change in their direction along frontal axis , except lead aVF . Thus Leads II & III switch places. (Replace each others) & leads aVL and aVR switch replace each others. Lead 1 reverse by 180* . However lead aVF remain unchanged. In the next few slides we will discuss “Understanding the ECG changes in Upper limb lead reversal ? Fig. A shows normally placed arm leads. A B Fig. B Shows lead reversal of left & right arm leads. ECG changes in Left arm (LA) & right arm lead (RA) reversal.
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Normal Einthoven triangle demonstrating the four limb electrodes (RA, LA, RL, LL) and the six leads generated by them (I, II, III, aVR, aVL, aVF). *RA=Right arm, LA = left arm , RL = Right leg , LL = left leg. Diagram summarizing the directions & polarity of the six limb leads. *Polarity of ECG leads means orientation of positive and negative ends of the ECG leads. Copied and modified from African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139
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*RA LA Left leg Right arm left arm lead reversal. Left leg Concepts. Understanding the changes in the polarity of the bipolar limbs leads due to Upper limb lead reversal. *Polarity of ECG leads means orientation of positive and negative ends of the ECG leads. Lead 11 Lead 11 Lead 111 Lead 111 Lead 1 Normal lead placement. Upper limb lead reversal. Lead 1 Copied and modified from Ari Edelheit, et al, ECG Pointers: Limb Lead Reversal MAY 3RD, 2018 ARI EDELHEIT CATEGORIES: ELECTROCARDIOGRAPHYPRACTICE UPDATES *RA=Right arm, LA = left arm , RL = Right leg , LL = left leg. *Lead 1 = RA- LA Lead 11 = RA - LL Lead 111 = LA- LL Lead 1 = LA- RA = Is truly 180* lead 1 reversal. Lead 11 = RA – LL = is truly lead 111 Lead 111 = LA- LL = Is truly lead 11 New polarity due to upper arm lead reversal Normal lead placement RA is changed to LA LA is changed to RA
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*RA LA LL Right arm left arm lead reversal. LA is changed to RA LL aVR aVL aVL aVR Normal lead placement. Upper limb lead reversal. Copied and modified from Ari Edelheit, et al, ECG Pointers: Limb Lead Reversal MAY 3RD, 2018 ARI EDELHEIT CATEGORIES: ELECTROCARDIOGRAPHYPRACTICE UPDATES *RA=Right arm, LA = left arm , RL = Right leg , LL = left leg. *aVR records an average voltage between LA - LL aVL records an average voltage between RA - LL Lead aVF records an average voltage between RA- LA *aVR = Average LA/LL , replaces aVL. aVL = Average RA/ LL ,replace aVR. aVF = average LA- RA , remain unchanged. Concepts. Understanding the changes in the polarity of augmented limb leads, due to upper limb lead reversal. *Polarity of ECG leads means orientation of positive and negative ends of the ECG leads. Lead 1 aVF Normal lead placement New polarity due to upper arm lead reversal aVF RA is changed to LA
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ECG below (Fig .B) shows ECG with upper limb reversal . Compare this with the corresponding normal ECG leads above (Fig A). Fig. A showing normal ECG limb leads. All waves in lead 1 are Inverted Lead 11 replaces baseline lead 111. Lead 111 replaces baseline lead 11. aVL gets inverted ,replaces baseline lead aVR aVR gets upright, replaces baseline lead aVL. A B African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139 African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139 Lead AVF remains unchanged.
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Fig. A showing normal 12 lead ECG Fig B shows 12 leads ECG recorded in a subject with left & right arms lead reversal. A B African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139 African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139 Note that in upper limb lead reversal , lead aVF & chest leads remain unchanged.
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Leads II and III switch places. (Replace each others) Leads aVL and aVR switch places.(Replace each others). Lead 1 has 180* reversal. lead aVF remain unchanged. Summary of the shifting of the leads polarity due to left arm , right arm lead reversal. Normal limb leads connections Shifting/replacement of limb leads associated with lead reversal. Copied & modified from https://litfl.com/wp-content/uploads/2018/08/ECG. Dr Ed Burns.
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Understanding the genesis of ECG Features in dextrocardia.
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ECG Features of Dextrocardia. Following ECG features of dextrocardia are commonly mentioned in the literature. 1. Lead I .Inverted P wave, negative QRS. 2. aVR . Upright P waves with Positive QRS complexes . 3. Chest leads. Absent R-wave progression in the chest leads (dominant S waves throughout & low voltage leads V5 &V6). 4. Right axis deviation (QRS). We will review few ECGs to observe the most consistent features of dextrocardia mentioned above. We will also discuss the electrophysiological background of these changes .
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Copied from https://www.facebook.com/MedicalMcq.page/photos/dextrocardia-ecg-characteristic-ecg-findings/1292071200826145/ Above ECG has all the four feature of dextrocardia . 1.Lead I .Inverted P wave, negative QRS . 2. aVR . Positive QRS complexes with upright P. 3.Chest leads. Absent R-wave progression in the chest leads (dominant S waves throughout & low voltage leads V5 & V6). 4. Right axis deviation (QRS). ECG recorded from a patient with dextrocardia.
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Copied and modified from https://ecg-educator.blogspot.com/2016/08/dextrocardia_43.html Above ECG has all the four feature of dextrocardia ,commonly mentioned in the literature. 1.Lead I .Inverted P wave, negative QRS . 2. aVR . Positive QRS complexes with upright P . 3.Chest leads. Absent R-wave progression in the chest leads (dominant S waves throughout & low voltage leads V5 & V6). 4. Right axis deviation (QRS). A. ECG recorded from a patient with dextrocardia.
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This ECG has feature of dextrocardia in all leads commonly mentioned in the literature, except aVR . 1. Lead I .Inverted P wave, negative QRS. 2. Chest leads. Absent R-wave progression in the chest leads (dominant S waves throughout . Low voltage leads V5 & V6. 3. Right axis deviation (QRS). 4.aVR has upright P wave but QRS instead of being upright is inverted . Copiied & modified from https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/tileshop_pmc_inline.html?title=Click%20on%20image%20to%20zoom&p=PMC3&id=6730946_18-244f1.jpg B. Another ECG in a patient with dextrocardia.
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Copied from https://www.grepmed.com/images/4980/electrocardiogram-dextrocardia-cardiology-reversal-clinical-inversus-situs This ECG has feature of dextrocardia in all leads mentioned in the literature except lead aVR. 1. Lead I .Inverted P wave, negative QRS . 2. Chest leads. Absent R-wave progression in the chest leads (dominant S waves throughout . Low voltage leads V5 & V6. 3. Right axis deviation (QRS). 4. aVR has negative QRS complexes with inverted P not expected in dextrocardia. C . Another ECG in a patient with dextrocardia.
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After review of these four ECGs we have observed that A. Three ECG features are most consistent in patient with dextrocardia. 1.Right axis deviation. (QRS ). 2. Lead I . Inverted P wave, negative QRS . 3. Chest leads. Absent R-wave progression in the chest leads (dominant S waves throughout . Low voltage leads V5 & V6. B. Changes in lead aVR may be inconsistent (variable ) . In the next few slides , based on the changes in the P & QRS vectors we will discuss following concepts. 1. How changes in the direction of P & QRS vectors results in the above ECG features of dextrocardia. ? 2. Why are the changes in lead aVR inconsistent ? First we will discuss the genesis of 3 ECG features that are most consistent in patient with dextrocardia.
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Copied &Modified From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif Spatial correlation of the P & QRS Vectors with the six limb leads in normal subject (Levocardia ). Mean axis of P & QRS vectors are directed inferiorly & left, around an angle of +45* to + 60*(Small and large Blue arrows). They are directed towards the positive ends of lead 1,11, aVF & 111, P & QRS are upright in these leads . However as the vectors are directed towards negative end of lead aVR, P & QRS waves in aVR are negative. Copied and modified from https://www.shutterstock.com/image-illustration/human-heart-made-four-chamber-left-1628034511 RA RV LA LV From http://www.ems12lead.com/wp-content/uploads/sites/42/2014/12/04-Negatives-+-Heart-+-Vector.png
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ppt slide no 114 content not found
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Copied &Modified From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif Why patient with dextrocardia has consistent ECG changes of right axis deviation & inverted PQRS in lead 1? Mean axis of P& QRS vectors are now directed inferiorly towards right around an angle of +130* to +150*QRS Thus patient with dextrocardia has right axis deviation.(large & small blue arrows). As they are directed towards the negative pole of lead 1, thus P & QRS waves are inverted in lead 1. This explains the consistent features of right axis deviation & inverted P &QRS in lead 1, in dextrocardia. Copied and modified from https://www.shutterstock.com/image-illustration/human-heart-made-four-chamber-left-1628034511 RA RV LV LA Copied and modified from https://ecg-educator.blogspot.com/2016/08/dextrocardia_43.html
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Posterior Copied & modified from https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif RA RV LV LA Anterior Understanding the reason for poor R-wave progression in the chest leads & low voltage leads V5 & V6 . In normal subject the mean axis of QRS vector (Fig A blue arrow )is directed towards positive poles of V4 –V6. Thus in normal subjects there is progression of R waves in chest leads V3 to V6 with tall R in leads V5 & V6. In dextrocardia mean axis of QRS (Fig B blue arrow )is directed away from positive poles of leads V4 –V6. This explains poor R-wave progression in the chest leads & low voltage leads V5 & V6. RA LV LA RV Copied &Modified From https://thoracickey.com/wp-content/uploads/2016/12/image00966-1.gif Fig A. Normal subject. Fig B. Patient with dextrocardia
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B +160* +130* In dextrocardia, rarely PQRS waves recorded in lead aVR may not be upright but flat/biphasic, Why ? In dextrocardia mean axis of P& QRS vectors are directed around an angle of +130* to +160*QRS, depending on the position of heart in the thorax. The mean axis of P &QRS shown in figure A are at +160* (Red arrow), which are closure to positive pole of aVR therefore upright P &QRS will be recorded in lead aVR. In the diagram B due to position of heart in thorax, the mean P & QRS axis is around +130.(Red arrow ). In such patient of dextrocardia mean axis is almost at right angle (80*) to lead aVR therefore P & QRS recorded in lead aVR will not be upright but recorded as biphasic or flat. + + Copied and modified from http://easyecg.weebly.com/limb-leads.html 80* A
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Summary of the ECG Features of Dextrocardia. Following ECG features of dextrocardia are commonly mentioned in the literature 1. Right axis deviation (QRS). 2. Lead I .Inverted P wave, negative QRS. 3. Chest leads. Absent or poor R-wave progression in the chest leads (dominant S waves throughout ). Low voltage V5 &V6. 4. aVR . Positive QRS complexes with upright P wave. Note that at times in some patients with dextrocardia , lead aVR instead of recording upright P waves may have biphasic or inverted P wave and or biphasic QRS. This may be due to variation in long axis position of heart in thorax.
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Differential diagnosis of inverted P & QRS waves in limb leads. Following are the three common causes of Inverted P & QRS waves in the limb leads, discussed . Situs inversus . 2 . Upper limb lead reversal . 3 . Dextrocardia. ECG in patient with upper limb lead reversal versus dextrocardia. ECG recording in a subject with left & right arms reversal resembles ECG finding of patient with dextrocardia. However, unlike dextrocardia there is normal R wave progression in the precordial (Chest ) leads. African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139 ECG recording in a subject with left & right arms leads reversal
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Post test. Don’t guess if you don’t know , select “ I don’t know”. You are expected to achieve minimum score of 75% If not please return to the pervious slides Read them carefully e t& retake the post test. Q 1.This ECG was recorded from a 40 years male with chest pain. Select the correct option. a. ECG is Suggestive of dextrocardia. b. ECG is suggestive of upper Limb lead reversal. c. Patient has Junctional rhythm . d. I don't know. African Journal of Emergency Medicine Volume 4, Issue 3, September 2014, Pages 130-139
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Copied and modified from https://ecg-educator.blogspot.com/2016/08/dextrocardia_43.html Q 2. This ECG was recorded from an asymptomatic 10 years boy. Select the correct option. a. He has dextrocardia. b. ECG is suggestive of limb lead reversal. c. He has isolated situs inversus. d. I don't know.
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Q3 .This ECG was recorded in a 50 years diabetic patient with chest discomfort. Select the correct option. a. Patient has Junctional rhythm . b. ECG is suggestive of Limb lead reversal. c. He has situs inversus . d. I don't know. Copied from https://ecgguru.com/ecg/ Donated by Michael Francis and Chris Burden..
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Copied from https://www.facebook.com/MedicalMcq.page/photos/dextrocardia-ecg-characteristic-ecg-findings/1292071200826145/ Q 4.This is ECG of a 30 years asymptomatic man who had applied for technician job. Select the correct option. a. He has dextrocardia. b. ECG is suggestive of limb lead reversal. c. He has isolated situs inversus. d. I don't know. Key is at the end of presentation.
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Ventricular hypertrophy . Left ventricular hypertrophy (LVH). Right ventricular hypertrophy (RVH).
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Left ventricular hypertrophy (LVH ). Pathophysiology. The increased LV mass in LVH generates stronger electrical signals , resulting in high voltage QRS . Additionally increased LV mass is associated with some degree of fibrosis. Greater myocardial mass & fibrosis prolongs conduction & may contribute to wider QRS duration. Third effect of LVH relates to the ST segment & T wave changes. Abnormal ventricular depolarization usually results in abnormal repolarization. Therefore, LVH is commonly associated with an abnormal ST & T wave changes. This is referred to as “LVH with strain” or “LVH with repolarization abnormality.” https://www.teachingmedicine.com/media/lessons/images/ECG%20grow%20sequence-2.png
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Understanding the ECG changes in LV hypertrophy (LVH). LV hypertrophy (LVH ) is associated with following ECG changes. 1. Increase in the voltage of the electrical signals resulting in high voltage QRS . 2.. Mild widening of the QRS wave. 3. Leftwards axis or left axis deviation. 4. ST depression (STD) & T waves changes In the next few slides we will discuss the mechanism “ concepts” of why & how LVH changes the ECG wave forms. Will discuss these under two headings. 1. High voltage QRS ,left axis deviation & QRS widening . 2. ST depression (STD ) & T wave changes.
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Understanding High voltage QRS ,left axis deviation & QRS widening in LVH . To understand this we need to review Ventricular depolarization vectors generating QRS in various ECG leads. These have been discussed in detail in the ECG grammar part 1, however we will briefly review these to facilitate our understanding of high voltage QRS in LVH.
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Copied & modified from https://www.cvphysiology.com/mCardiovascular Physiology Normal ECG generated by LV depolarization vectors in limb leads. (Frontal electrical plan ) Fig A shows normal ventricular depolarization (QRS ) vectors with superimposed limb leads direction & polarity map. QRS vector 2 & 3 are main vectors responsible for depolarization of LV apex & LV free wall respectively( Fig. A red arrows 2 & 3 ). The mean QRS axis shown in Fig. A (Green arrow) is around +40* to +60* directed toward positive poles lead 11 . *Thus lead 11 records tall R wave where as in lead aVL QRS is biphasic as the mean vector is almost at right angle to aVL ,Fig B. How does the QRS vectors in LVH change the ECG morphology in the limb leads , will be discussed in next three slides. *Based on rules of electrical conduction across myocardial cell. B A - aVR Inferior . Superior.
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11 Normal Leads 11, aVL. How does the QRS vectors in LVH changes the ECG morphology of the limb leads (Frontal electrical plan ) ? A Fig A. Showing normal ECG with mean QRS axis around +40* to + 60* ,generating tall R in lead 11 & almost biphasic in lead aVL. Fig B. ECG is patient with severe LVH .Mean QRS axis is showing left axis deviation -35* to 45* directed toward negative pole of lead 11. Thus recording deep S wave in lead 11 & tall R wave in lead aVL. In mild to moderate LVH , leftward deviation of mean axis may be 0* to -15* . https://line.17qq.com/articles/qgnqkkqfqy.html B Leads 11 & aVL In Severe LVH
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Anterior A Copied from http://www.ems12lead.com/wp-content/uploads/sites/42/2014/12/04-Negatives-+-Heart-+-Vector.png Posterior Left lateral. Copied & modified from https://www.cvphysiology.com/Cardiovascular Physiology Concepts. Normal ECG generated by LV depolarization vectors in chest leads . Fig A shows normal ventricular depolarization (QRS ) vectors with superimposed chest leads location map. QRS vector 2 & 3 are main vectors responsible for depolarization of LV apex & free wall respectively( Fig. A red arrows ). Main vector & vector 3 , depolarizing LV free wall , is directed toward the positive pole of V5 & V6 & away from lead V1. Thus leads V5 &V6 record tall R & lead V1 deep S wave ( Fig B ). How does the QRS vectors in LVH change the ECG morphology of the chest leads will be discussed in the next slide? B
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Normal How does the QRS vectors in LVH change ECG morphology of the chest leads (short axis electrical plan ) ? A Fig A. Showing normal six chest leads ECG . Compare this with ECG in patient with LVH fig B, with higher voltage R wave in V5-V6 (25 mm )& deeper S wave in V1-V2 (25 mm ). Why does LVH generate high voltage QRS in chest (precordial ) leads ? There are mainly two reasons. Greater LV mass in LVH generates higher magnitude QRS vectors & higher electrical (QRS) signals. Additionally due to thick LV free wall, mean QRS & vector 111 are shifted towards left .Compare fig C1&C2 . Thus these QRS vectors are better aligned with the positive electrodes of V5 –V6 & directed at 180* (away from positive poles of ) lead V1-V2 https://line.17qq.com/articles/qgnqkkqfqy.html Severe LVH https://ecgwaves.com/wp-content/uploads/2017/03/ecg-left-ventricular-hypertrophy-right-ventricular-hypertrophy-criteria-ekg.jpg Normal Severe LVH B C1 C2 This explains high voltage (Tall ) R wave in leads V5-V6 & deep S wave in lead V1. Additionally due to thickened myocardium & fibrosis electrical conduction takes longer , resulting in slight widening of QRS .(Compare QRS width in figures A & B ).
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Summary. Impact of LVH on the the QRS vectors & ECG in limb & chest leads. Limb leads. Hypertrophied LV generates high magnitude vectors 11 & 111. The mean QRS axis is shifted towards left, from normal +60* to 0* -40*. This results in high voltage R wave in lead aVL & deeper S wave in lead 11.(This explains left axis deviation.) Chest leads. Similarly greater LV mass & leftward directed mean QRS axis generates higher electrical signals recording high voltage R waves in V5 –V6 & deep S waves in V1-V2. Due to thickened myocardium & fibrosis ,electrical conduction takes longer,resulting in slight widening of QRS .
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https://www.teachingmedicine.com/Lesson.aspx In LVH , high magnitude QRS vector of the LV free wall ( Fig. A, yellow arrows) are better aligned with & directed closely towards positive electrode of V5 -6 generating high voltage R waves in these leads. Fig. B2. At same time these vectors are moving away from the V1-V2 recording deep S waves in VI –V2.(Fig. B1 ). Illustrative explanation of the genesis of high voltage QRS in Left ventricle hypertrophy (LVH). Copied & modified from https://ecgwaves.com/wp-content/uploads/2017/03/ecg-left-ventricular-hypertrophy-right-ventricular-hypertrophy-criteria-ekg.jpg A B2 Posterior. B1
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In LVH, the S waves in V1-V2 are amplified. It is measured from isoelectric line up to tip of the S wave down (Fig, A. Horizontal blue lines ). As discussed R waves in V5 – V6 are amplified (Fig B). It is measured from isoelectric line up to the tip at the top of R wave (Fig, B. Horizontal blue lines). https://www.teachingmedicine.com/Lesson.aspx A B Measurements of S & R waves recorded in ECG.
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ST segment depression (STD ) & T waves changes in LVH without coronary artery disease . The other common impact of LVH on ECG is *STD & T waves changes . ^Left ventricular hypertrophy (LVH ), without coronary artery disease, can cause typical repolarization abnormalities ST segment depressions (STD) and T-wave inversions in the lateral leads, This is commonly referred to as the LV ^strain pattern in the literature. However the AHA recommendations promote the use of the term "LVH with secondary ST-T wave abnormalities" instead of "strain“. Additionally LVH may be associated with non-specific ST-T changes that could not be distinguished from those of coronary artery disease. This may adversely affect the accuracy of the ECG criteria for the diagnosis of left ventricular hypertrophy .” ^LV strain pattern by itself has a 52% sensitivity in the recognition of LVH with a specificity nearing 95%..
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Copied & modified from. https://www.jaypeedigital.com/eReader/chapter/9789350904893/ch1 Primary and secondary T-wave abnormalities. Primary T-wave abnormalities (ischemia or injury) are due to alterations in myocardial cellular electrophysiology . Secondary T-wave abnormalities ( In bundle branch block or ventricular Hypertrophy etc ) are subsequent to alterations of sequence of ventricular ( activation ) depolarization. Secondary T wave changes. Primary T wave changes
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Location of STD. STD attributable to ischaemia is often diffuse and can be located in either anterior & or nferior leads. Location of STD.. STD is commonly located in the leads with high voltage R waves (anterolateral leads ) V4 to V6 aVL & lead 1 *STD= ST segment depression. Character of ST depression (STD). Two ECG changes favors Ischemia. At least 1.0 mm (0.10 mV) depression at the J point . With either horizontal or downward sloping STD Character of ST depression (STD). LVH strain pattern is characterized by down sloping STD > 1 mm (0.10 mV) usually without J point depression. *STD & T wave changes in LVH without coronary artery disease versus STD & T wave changes due to myocardial ischemia. ^Strain pattern by itself has a higher sensitivity ( 52% ) in the recognition of LVH with a specificity nearing 95 %. Duration of ECG changes. The strain pattern usually doesn’t change over short period . Duration of ECG changes. As compared to strain , ischemic STD have dynamic changes as seen in acute coronary syndrome (ACS ). Character of T wave inversion Ischemia is associated with primary T wave inversion. T wave inversion is symmetric . STD in LVH without coronary artery disease ^(LV strain ). STD coronary artery disease (Ischemia ). Character of T wave inversion . STD is associated with Secondary T wave changes . These are asymmetrical, with gradual down sloping & a rapid return to baseline,
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ECG showing characteristics of severe LVH. High voltage S waves V1- V2 & R waves in V5 –V 6 , with left axis deviation( around ( – 60*). Delayed conduction causes widening of the QRS, increased R wave (Peak time of >50ms in leads V5- V6). Repolarization abnormalities ,ST depressions with asymmetric T wave inversions in leads V5-V6, 1 & aVL . LVH with strain, T wave inversions are often asymmetric, Copied from https://rushemergencymedicine.org/2018/11/01/5-minute-ekg-in-a-rush/
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Mechanism of *STD & T wave changes in LVH with normal coronary arteries. LVH with normal coronary arteries may be associated with two types STD & T wave changes. 1. Typical repolarization abnormalities "LVH with secondary ST-T wave abnormalities (LV strain)”. 2. ST-T changes that may not be distinguished from those of coronary artery disease changes. 1. Typical repolarization abnormalities "LVH with secondary ST-T wave abnormalities (LV strain)”.. Greater myocardial mass & fibrosis prolongs depolarization which results in delayed LV repolarization . Due to delayed LV repolarization, RV repolarization starts & ends earlier . Therefore RV surface has positive charge (due to repolarized cells) , where as LV has not yet repolarized completely & has negative charge. Thus negative end of vector of repolarization is directed toward positive electrode of V5 V6 generating (STD) & secondary T-wave abnormalities. (See secondary ST-T changes in LBBB slide 28). This is better illustrated in the next slide. *F U Huwez, S D Pringle, P W Macfarlane ,Variable patterns of ST-T abnormalities in patients with left ventricular hypertrophy and normal coronary arteries; Br Heart J 1992;67:304-7. *STD= ST segment depression.
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+ _ Due to hypertrophy & fibrosis, LV repolarization is delayed & RV repolarization starts & ends earlier. RV surface has positive charge , due to repolarized cells, where as LV has not yet repolarized & has negative electric charge. + + _ + _ _ _ Positive electrode ( V6 ) Figure A is showing hypertrophied LV Vector of repolarization Delayed LV repolarization Mechanism of STD in LVH Secondary ST- T changes in LVH. RV LV + Thus negative end of the repolarization vector is directed toward positive electrode of V5 & V6 generating inverted T waves ( Fig. B ). Copied & modified from. https://www.mayoclinic.org/-/media/kcms/gbs/patient-consumer/images/2013/08/26/11/03/ds00680-ans7_lvhthu_jpg.jpg A Copied from https://ecgwaves.com/wp-content/uploads/2017/03/ecg-left-ventricular-hypertrophy-right-ventricular-hypertrophy-criteria-ekg.jpg B
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Mechanism of two types of * STD & T wave changes in LVH with normal coronary arteries (Continued ). 1.Typical repolarization abnormalities of STD in LVH with LV strain ( Already discussed in last slide ). 2. ST-T changes that may not be distinguished from those of coronary artery disease changes. As explained by in is study ,*F U Huwez states that “The mechanism for these (type 2 ) ST-T abnormalities that do not accord with the definition of left ventricular strain is difficult to explain ” . This is because the coronary arteries in the study subjects were normal. “ But it is well established that myocardial ischaemia may present on the surface ECG manifesting as flat ST segment depression, flat T waves, symmetrical T inversion, or non-specific ST-T abnormalities.” *Conclusion. “Left ventricular hypertrophy (LVH) without coronary artery disease can cause variable types of ST-T abnormalities in the anterolateral leads including the typical left ventricular strain pattern and non-specific ST-T changes. Non-specific abnormalities could not be distinguished from those of coronary artery disease and may adversely affect the accuracy of the electrocardiographic criteria for the diagnosis of left ventricular hypertrophy because they do not accord with the criteria for left ventricular strain “. *F U Huwez, S D Pringle, P W Macfarlane ,Variable patterns of ST-T abnormalities in patients with left ventricular hypertrophy and normal coronary arteries; Br Heart J 1992;67:304-7. *STD= ST segment depression.
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ECG criteria for Left ventricular hypertrophy. There are several electrocardiographic criteria and scoring systems proposed for diagnose of LVH. Copied and modified from. https://www.grepmed.com/images/3803/left-lvh-ventricular-ekg-voltage Reference for further study. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram Part V: Electrocardiogram Changes Associated With Cardiac Chamber Hypertrophy :(Circulation.2009;119:e251-e261.) Common ECG criteria of LVH
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https://www.teachingmedicine.com/media/lessons/images/ECG%20grow%20sequence-2.png "Sokolow and Lyons Criteria” Uses the sum of deepest S wave in V1 and the tallest R of V5 or V6 > 35. In this example, the S wave in V1 = 24 and the R wave in V5 = 42 and total = 66, so criteria is met. https://www.teachingmedicine.com/Lesson.aspx
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"aVL Criteria" (also by Sokolow and Lyons) R in aVL > 11 mm. https://www.teachingmedicine.com/Lesson.aspx
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Cornell criteria based on R in aVL + S in V3 In this example, the R in aVL = 20 and the S in V3 = 20 for total of 40 mm, so criteria is met for either a man or woman. https://www.teachingmedicine.com/Lesson.aspx
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Supportive ECG criteria for LVH. ECG features which Increase specificity (diagnostic accuracy) of LVH. Following ECG features are not required for the diagnosis of LVH, but if they are present, they increase the specificity of LVH diagnosis ,make it more accurate. Left atrial enlargement (LAE).(With out associated mitral valve stenosis) ST and T wave changes .(Left precordial leads ). Wide QRS . Left axis deviation. In other words, an ECG that demonstrates voltage criteria plus left axis deviation , LAE & Strain pattern is more likely to be "truly LVH" compared to an ECG with the same voltage criteria without above extra features.
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What is sensitivity and specificity of ECG for LVH ? There have been several ECG criteria and scoring systems proposed for diagnosis of LVH with variable sensitivity & specificity. However over all these criteria have reasonably high specificity but low sensitivity. Results of study by *Maxwell Bressman et al to determine Sensitivity and Specificity of ECG for LVH in diverse patient population is summarized below. “Results: 13,960 subjects were included in the study. The typical subject were 60 years of age or older, female, overweight, hypertensive, and demonstrated low socioeconomic status.” “The sensitivity and specificity of ECG for LVH in the overall cohort were 30.7% and 84.4%, respectively, with multiple patient characteristics influencing these results.” “However, despite adequate specificity, the sensitivity to detect LVH using a wide variety of ECG criteria have ranged from only 12% to 29%.” *Maxwell Bressman et al Determination of Sensitivity and Specificity of Electrocardiography for Left Ventricular Hypertrophy in a Large, Diverse Patient PopulationMarch 17, 2020DOI:https://doi.org/10.1016/j.amjmed.2020.01.04
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Right ventricular hypertrophy
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Right ventricular hypertrophy (RVH). The diagnosis of right ventricular hypertrophy (RVH) can be made on ECG. However, the diagnostic criteria are not particularly sensitive nor specific. Echocardiography is a better modality to diagnose RVH, but ECG does have clinical value.
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Figure A showing thick right ventricle ( Yellow color arrows). This generates strong electrical signals in RV directed anteriorly , toward V1 away from V6 (Fig B blue arrows) . Due to this ECG will record high voltage R wave in V1 & deep S wave in V6. In normal ECG, there is deep S wave in V1 & tall R in V5/V6 . In RVH the pattern is reversed as mentioned above. ECG changes will be discussed in next slide. https://www.teachingmedicine.com/Lesson.aspx A B Posterior Posterior Understanding the genesis of ECG changes in right ventricular hypertrophy.
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Normally R:S ratio in lead V1 is < 1 . (R wave is smaller than S wave) & in lead V5-V6 R:S ratio >1 (R wave voltage is > S wave).Fig. A. In RVH normal R:S is reversed .R:S ratio in lead V1 is ≥ 1 (Voltage of R wave is ≥ S wave) & R:S wave in V6 ≤1 (Voltage of R wave is ≤ S wave ). Fig. B. R:S ratio > 1 in V1 is suggestive for, but not specific for RVH. It can be present in several other conditions. A Copied from https://www.cvphysiology.com/ Cardiovascular Physiology Concepts. Copied from https://ecg.utah.edu/test/5 B R wave & S wave (R:S ) ratio in leads V1 and V6 criteria for right ventricular hypertrophy ( RVH ). Normal chest lead ECG. Chest lead ECG in RVH.
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https://www.teachingmedicine.com/media/lessons/images/ECG%20grow%20sequence-2.png Summary of diagnostic ECG criteria supporting RVH. Tall R wave in V1 > 6mm R:S ratio > 1 in V1 R:S ratio < 1 in V6 Right axis deviation (RAD) Right atrial enlargement (RAE) ECG is not the best method to diagnose RVH and the criteria are somewhat variable. Reference for further study. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram Part V: Electrocardiogram Changes Associated With Cardiac Chamber Hypertrophy :(Circulation.2009;119:e251-e261.).
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What is sensitivity and specificity of ECG for RVH ? ECG criteria ^(reported in the literature )has high specificity but very low sensitivity (often <10%) for identifying MRI-detected RVH. Why ? RVH causes a displacement of the QRS vector toward the right & anteriorly, opposite to that of LV. However, significant degrees of RVH is often required to change the balance of right and left ventricular vectors . Why ? This is because normal LV free wall is more than twice (> 8mm) thicker than RV free wall (<5mm ). Therefore vectors of LV activation dominates in the normal heart & even in mild RV hypertrophy. Thus, the ability of the ECG to detect mild RVH is low. This explains low sensitivity of ECG criteria for RVH. Isaac Whitman et al, Validity of the Surface Electrocardiogram Criteria for Right Ventricular Hypertrophy: The MESA - Right Ventricle Study , J Am Coll Cardiol. 2014 Feb 25; 63(7): 672–681
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Post test (Slide 119 ) Key Q 1 B. Q 2 A Q 3 A. Q 4 . A