The Early Signs of Right Bundle Branch Block - Chest

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‘ rgt I vI L 1111 14 N H j I. II I, I II I I “ . I I :, #{149}‘ : ‘ i ii I FIGURE 2. Electrocardiogram (standard lead 2 and continuous strip oflead V2) ofcase 1. I I --4-- - - E I .1 -ri -UI I I - FIGURE 3. Diagram illustrating atria! flutter with alternating 2:1 and 4:1 A\7 conduction ratios. FIGURE 4. Electrocardiogram (a continuous strip of lead V,) of case 2. shortening of the S wave with inversion of the T wave. This is also evident in the first two beats ofthe second strip. The remaining beats of the second strip, as well as the first four beats of the third strip, show incomplete right bundle branch block, as evidenced by a small Downloaded From: http://journal.publications.chestnet.org/ on 03/27/2013 ‘ I 1- I I 1 - _1 t I i .. i I terminal r’ deflection. The r’ deflection varies in amplitude depend- ing on the degree of incomplete right bundle branch block, and is more marked when associated with shorter cycles, eg, 0.80 sec. The long pause following the ventricular extrasystole in the third strip is CHEST / 87 / 2 I FEBRUARY, 1985 181
. I :1 1. I I :I 1.:j .I :Ii.J I.1.:’ITRI fH.:::UI I.IF;- - JTiii.I- I ‘flTh j. ... .l..1....I “.1- I #{149} , C 1-I----r-----i---r V.1 . .1 I I -r--r 1r..H FIt j:: I I #{149} :. J I: II#{149}l F :I:.IH ITI I 1 ! C I I I I r I I I I II I VI’ . ‘ 1 followed l)) three l)eats which, as before, have a deep S wave. The last beat ofthe third strip, as well as the first three beats ofthe bottom strip, are once again associated with short S waves. In addition, there is some slurring ofthe ascending limb ofthe S wave as it approaches the baseline in these beats. The last eight heats are yet again associated with deep S waves. The various QRS manifestations are dependent on critical rate. Thus, at a sinus cycle of0.83 sec or less, the heats have a relatively short S wave. With a sinus cycle greater than 0.83 sec. the beats have a deep S wave. The manifestations are thus an expression of aberrant ventricular conduction which is dependent on critical rate. CASE 3 The ECG (Fig 5, a continuous strip of lead V,) reflects very long P-P intervals, which range from 1.88 to 2.14 sec. This represents either (a) a marked sinus bradvcardia of28 to 32 heats/minute, or (b) a sinus rate of56 to 64/minute complicated by 2:1 sinoatrial block. The first conducted sinus heat is the second beat ofthe top strip. This is followed by an AV nodal escape beat. The ensuing P wave occurs 0.38 sec after the escape beat and is conducted with right bundle branch block aberration. The sequence ofescape and capture constitutes a form ofescape-capture bigeminy The next escape heat (the last heat in the top strip) occurs synchronously with the P wave (concealed within the QRS complex), whose impulse is consequentl interfered with and not conducted. These conduction sequences occur throughout the tracing. The capture beats are associated with the following forms of intraventricular conduction: 1. Normal intracentncular conduction: This occurs with the second beat ofeach strip and the last beat ofthe bottom strip. These are associated with R-P intervals of0.66, 0.62, 0.60, 0.64, and 0.52 sec. respectively. 2. Right bundle branch block: This occurs with the fourth heats of the first and second strips, which are associated with R-P intervals of 0.35 sec. ::ll4:;l4::l: lf.lL !i I1iI I I’--h-!-_.( . I _,U_I I 1LL I I __I. I I ‘“ III I I I I I 11 I III I I 1_I I I i I I II I L I I I I 1_i ft I 1 1 If I I I I .:Ifl1 IIIV1 I I’+-ILMll H.i1 H41 ‘+fl I I L 111 I ‘+-4. ‘$41 Ill I III Itl k-+’4(Th4 I U I I 4tfl U4IUIU 1itE1fifTh ±H±LLL±iH±E TLLLt±JjHjj44jftLUI!JHU.1ILLL FIGURE 6. Electrocardiogram (a continuous strip oflead MCL1) ofcase 4. 182 Early Signs of Right Bundle Branch Block (Schamroth, Myburgh, Scharnrofh) Downloaded From: http://journal.publications.chestnet.org/ on 03/27/2013 - - U- FIGURE 5. Electrocardiogram (a continuous strip of lead V,) ofcase 3. 3. Diminished S wave: This is reflected by the fourth beat of the third strip, and is associated with an R-P interval of0.38 sec. The form ofthe intraventricular conduction is thus dependent on the R-P interval. The late impulses ofrelatively long R-P intervals are associated with normal intraventricular conduction. The early impulses of relatively short R-P intervals are associated with right bundle branch block conduction. An intermediate R-P interval is associated with a QRS complex that merely shows a diminished S wave. CASE 4 The ECG (Fig 6, a continuous strip oflead MCL1) shows a basic fast sinus rhythm in the upper strip. The P-P intervals measure 0.66 sec. representing a rate of9llminute. The second beat in the top strip is a ventricular extrasystole. The rhythm is further complicated by atrial extrasystoles, which are conducted with right bundle branch block aberration. These are represented by the 9th and 14th beats in the top strip, and the 5th and 10th beats in the bottom strip. The P wave of each atrial extrasystole is superimposed upon and deforms the ST segment ofthe preceding beat. The second atrial extrasystole ofthe bottom strip falls during the vulnerable period ofthe atria and precipitates atrial fibrillation, as is evidenced by the ensuing fast irregular rhythm. Some ofthe beats during the atrial fibrillation also reflect the rsR’ configuration of right bundle branch block aberration. The fourth beat of the top strip is of particular interest and merely reflects a diminution ofthe S wave as the only change. This beat is preceded by a long cycle occasioned by the pause of the ventricular extrasystole. A long pause, by virtue of the Ashman phenomenon, will increase the ensuing refractoriness and therefore favor aberration. The diminished amplitude of the S wave thus represents a degree of aberration which, in view of the classic right bundle branch block aberration associated with the atrial extrasystoles, represents an early phase ofright bundle branch block. The diminution ofthe S wave in the last beat ofthe top strip and the last I
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The Early Signs of Right Bundle Branch Block - Chest

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