Vectorcardiographic features of left anterior hemiblock combined with complete right bundle branch block

J. ELECTROCARDIOLOGY, 4 (4) 322-330, 1971

Vectorcardiographic Features of Left Anterior Hemiblock Combined with Complete Right Bundle Branch Block* BY ALBERTO BENCHIMOL, M.D., KENNETH B. DESSER, M.D., AND EGEU C. ]3ARRETO, M.D. With the Technical Assistance of Bettie Jo Masse3'

SUMMARY

Superior displacement of the frontal plane QRS loop of the vectorcardiogram in the The vectorcardiographic features of left presence of RBBB has been previously attribanterior hemiblock (LAHB) combined with uted in four cases to "intrainfarction" block right bundle branch block (RBBB) were or "left ventricular parietal blockS. '' Owing characterized using the Frank lead system. In the presence of RBBB, the following criteria to the uncertain origin of this superior frontal appeared to be most useful for the additional plane orientation, this pattern has also been diagnosis of coexisting LAHB: Superior dis- allocated the title "atypical" right bundle placement and counterclockwise inscription branch blockL The possibility that this combiof the frontal plane QRS loop, and QRS nation of vectorcardiographic abnormalities duration of 120 msec or more, with delayed represented a variant of "bilateral bundle inscription of the terminal 60 msec vectors. branch block" was considered in 1966~; and LAHB combined with RBBB results in a RBBB combined with block of the superior more superior frontal plane maximum QRS division of the left bundle branch, four years later 8. In the latter study, however, the modivector than does isolated RBBB or LAHB. fying effects of RBBB on the vectorcardiographic manifestations of isolated LAHB and INTRODUCTION the frequency of coexisting myocardial inAn appreciation for the trifascicular nature farction were not expanded on. Based on 41 of the conduction system of man has led to a vectorcardiograms from patients showing the more complete understanding of intraven- electrocardiographic findings of isolated tricular conduction abnormalities 1. Clinical, LAHB, criteria have been recently set forth anatomic and pathologic studies *'4 have dem- for the vectorcardiographic diagnosis of this onstrated that the electrocardiographic syn- conduction disturbance 9. Utilizing these latter drome of frontal plane abnormal left axis criteria and existing criteria for the vectordeviation (LAD) above --45 degrees com- cardiographic diagnosis of RBBB 6, it appears bined with complete right bundle branch that LAHB combined with RBBB can be block (RBBB) is based on simultaneous block diagnosed vectorcardiographically. of the left anterior-superior fascicle (left anThe purpose of this paper is to characterize terior hemiblock - LAHB) and the right the vectorcardiographic features of LAHB bundle branch. combined with RBBB utilizing the Frank lead system. Furthermore, the influence of coexisting myocardial infarction on this pat*From the Institute for Cardiovascular Diseases, tern and comparison with isolated LAHB Good Samaritan Hospital, 1033 East McDowell will be described. Road, Phoenix, Arizona 85006. S u p p o r t e d in part by the Nichols' Memorial Fund. MATERIALS AND M E T H O D S R e p r i n t requests: Alberto Benchimol, M.D., The study group was comprised of 28 Good Samaritan Hospital, 1033 East McDowell patients. There were 23 men and five women Road, Phoenix, Arizona 85006. 322

323

VCG IN LAHB WITH RBBB

whose age ranged from 13 to 88 years with a mean of 65 years. All patients manifested electrocardiographic evidence of combined L A H B and RBBB as described by RosenbaumL The criteria for this diagnosis include abnormal frontal plane LAD with deep S waves in leads II, I I I , and aVF of the electrocardiogram associated with precordial lead evidence of complete RBBB. All cases with Q waves in leads II, I I I , or aVF, had monophasic negative complexes without terminal R waves. There were 14 patients with coronary artery disease and 14 patients with cardiovascular disease of other etiology. In this latter group, there were four patients with primary myocardial disease, three patients with essential hypertension, three patients with Stokes-Adams syndrome of unknown etiology, two patients with chronic obstructive pulmonary disease, and one each with

E.C.

- 84

mesocardia and common A-V canal. All diagnoses were based on complete history, physical examination, and chest roentgenograms. Patients with coronary artery disease were considered to have experienced an acute myocardial infarction on the basis of chest pain of more than one hour's duration, enzyme changes, and serial electrocardiographic and vectorcardiographic findings compatible with this diagnosis. A 12-lead electrocardiogram was taken in each case with a standard direct writer electrocardiograph. Vectorcardiograms in the three plane projections were recorded in the supine position using the Frank lead system ~~ The fourth intercostal space was used for placement of the chest elctrodes as sugge~ed by Langner et al ~ for the supine position. The vectorcardiograms were recorded in DR-8 Electronics for Medicine light beam

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Fig. 1. Vectorcardiogram and electrocardiogram from an 84 year old man with congestive heart failure of uncertain etiology, LAHB and RBBB. The frontal plane (FP) QRS loop rotates counterclockwise and is superiorly oriented with the initial 20 msec vectors directed inferiorly; the terminal 60-160 msec QRS vectors are delayed, all characteristic of LAHB associated with RBBB. In the horizontal plane (HP) there is a terminal, anteriorly directed appendage of the QRS loop. Note also the delay of inscription of the terminal 60-160 msec vectors, characterhtic of KBBB. J. E L I E C T R O C A R D I O L O G Y , V O L . 4. N O . 4 ,

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BENC HIMOL ET AL

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Fig. 3. Mean direction in degrees and mean magnitude in mv of the 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 msec and of the maximum QRS vectors from 28 patients with LAHB and RBBB. oscilloscopic photographic recorder using a vectorcardiographic channel (Model VET-6). Still and timed vectorcardiograms (running loops) were taken in the frontal, left sagittal and horizontal planes. The still loops were magnified in order to provide a better analysis of the initial and terminal components

of the QRS loop; this degree of magnification averaged from 50-80 mm for 88 inv. Timed vectorcardiograms were taken at paper speeds of 75 to 100 mm/sec using previously described techniques 12,13. The loops were interrupted at intervals of 2 msec; the direction of rotation was indicated by a comet with J. ELI~CTROCARDIOLOGY, VOL. 4, NO. 4, 1971

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ferior wall infarction14. All eight patients had clinical evidence of coronary artery disease, and six had definite history of myocardial infarction. We have found this initial clockwise rotation a useful sign for the diagnosis of coexisting LAHB and inferior wall myocardial infarctiontS,t6. Duration: The duration of the QRS loop ranged between 120 and 170 msec, and a significant delay of inscription beyond the 60 msec QRS vectors was a constant feature.

Rotation: Twenty-four of 28 (85%) patients manifested a counterclockwise rotation in this plane, and in the remaining four cases, the rotation was a figure-of-eight. These findings are in agreement with the rotation observed in isolated LAHB 9. A typical vectorcardiogram from a patient with LAHB and RBBB is shown in Fig. 1. In eight cases, the initial 20-30 msec QRS vectors rotated in a clockwise fashion, similar to patients with in-

Direction: The direction and magnitude of the frontal plane QRS vectors are shown in Figs. 2 and 3. In 20 of 28 cases, the initial 10 and 20 msec vectors were oriented inferiorly and to the left or right. In all cases~ the balance of the QRS loop beyond the inscription of the 20 msec vector was displaced superiorly and to the left, as has been previously noted with isolated LAHB% In our study group, the three major differences be-

the "tail" pointing in the direction of inscription. The following measurements of the QRS loop were made in all vectorcardiograms: 1) direction and magnitude of the 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 and 110 msec QRS vectors in the three planes, 2) direction and magnitude of the maximum QRS deflection vector and 3) rotation of the QRS loop. RESULTS

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Fig. 4. Vectorcardiogram and electrocardiogram from an 88 year old man with an old inferolateral myocardial infarction, LAHB and RBBB. In the fronta plane, the initial 20-30 msec QRS vectors are directed superiorly and rotate clockwise, indicating an inferior wall infarction. I n the horizontal plane, the initial 30-40 msec QRS vectors are directed to the right and anteriorly, suggestive of lateral wall infarction 6. J. ELECTROCARDIOLOGY,

VOL.

4.

NO.

4,

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BENCHIMOL

tween isolated LAHB and LAHB combined with RBBB were: (1) the initial 10-20 rasec QRS vectors tended to be directed more to the right (max. vector 134-114 ~ with combined LAHB and RBBB compared with isoloted LAHB (max. vector 80-44~ (2) the mean maximal QRS vector was oriented more superiorly (--53 ~ with LAHB and RBBB compared with isolated LAHB (--19 ~ ; and (3) the 70-120 msec QRS vectors, because of the influence of RBBB 6, were oriented to the right. In eight cases, all with coronary artery disease and six with a previous history of myocardial infarction, the initial 20.30 msec QRS vectors were directed superiorly suggesting coexisting inferior wall myocardial infarction 14. This superior displacement of the 20-30 msec QRS vectors associated with initial clockwise rotation is strongly indicative of coexisting inferior wall infarction. The vectorcardiograms and electrocardiograms from such a patient are shown in Fig. 4.

ET AL

Sagittal Plane Rotation: In five cases the QRS loop rotated clockwise, in nine counterclockwise, and in 14 figure-of-eight. This contrasts with isolated LAHB, which results in a counterclockwise rotation in 58% of cases~ Duration: As in the frontal plane, the

QRS duration was between 120 and 170 msec, with a significant delay beyond the inscription of the initial 60 msec QRS vectors. Direction: The direction and magnitude of the sagittal plane QRS vectors are shown in Figs. 3 and 5. The QRS loop tended to be displaced anteriorly, especially beyond the inscription of the 40 msec QRS vectors. This contrasts with isolated LAHB, which results in 40-70 msec QRS forces directed posteriorly in over 90% of cases9. In six cases with previous history of myocardial infarction, the initial 20-30 msec QRS vectors were directed superiorly. This orientation associated with early sagittal plane clockwise rotation was

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VOL. 4, NO. 4, 1971

VCG I N L A H B W I T H R B B B

327

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Fig. 6. Direction of the 10, 20, 40, 60, 100 msec and of the maximum QRS deflection vectors in the horizontal plane from patients with LAHB and RBBB. The mean value for each vector is indicated. strongly suggestive of coexisting inferior wall infarction (Fig. 4) 14.10. Horizontal Plane Rotation: Using the classification of Baydar et aW for RBBB, the distribution of the horizontal plane loops in our study group were as follows: Type I (initial inscription counterclockwise) - 18 patients, Type II (initial clockwise rotation with a figure-of-eight loop) - five patients and Type III (complete clockwise rotation) - five patients. Duration: The QRS loop duration in this plane was 120-170 msec with a significant delay of inscription beyond the initial 60 msec QRS vectors. Direction: The direction and magnitude of the horizontal plane QRS vectors are shown in Figs. 3 and 6. Compared with isolated LAHB 9, the mean values for the 10-70 and maximum QRS deflection vectors with LAHB and RBBB in our study group were J. E L E C T R O C A R D I O L O G Y , V O L . 4, N O . 4, 1971

oriented more to the right (Table I). The mean direction values for the terminal 70-120 msec vectors were anteriorly and to the right, similar to uncomplicated RBBB 6. Five patients with Type I a n d all patients with Type II configurations had 80-100% of their horizontal plane QRS loops directed anteriorly. In six patients, both efferent and afferent limbs of the QRS loop were anterior to the X axis. A single patient with documented anterior wall myocardial infarction manifested a 20 msec QRS vector which was directed posteriorly. This subject displayed electrocardiographic evidence of "standard" and "precordial masquerading bundle branch block," LAHB, RBBB, anteroseptal infarction and first degree atrioventricular block (Fig. 7). DISCUSSION On the basis of electrocardiographic analysis, it has been proposed that, when LAHB

328

BENC HIMOL ET AL

TABLE I Comparison of the Mean Direction of the 10, 20, 30, 40, 50, 70 msec and of the Maximum:QRS Deflection Vectors in LAHB and LAHB with RBBB in the Horizontal Plane ( In Degrees) QRS Vectors msec

LAHB

LAHB and RBBB

88

127

20

36

91

30

--13

26

40

--55

50

--61

--24

70

--90

146

Max.

--40

40

10

1

and RBBB are coexistent, LAHB and RBBB account for the initial and terminal 60 msec QRS abnormalities, respectivelyis. Impulses conducted through the intact left posteriorinferior fascicle result in early lower septal and left ventricular infero-apical depolarization 9. The segment of the left ventricular myocardium supplied by the blocked left anterior division is then activated, accounting for forces oriented in a superior direction. With combined LAH'B and RBBB, the frontal plane maximum QRS vector is directed more superiorly compared with that of isolated LAHB. This apparent leftward deviation attributed to RBBB has been noted before in cases of isolated LAHB, which manifested a more superior frontal plane electrocardiographic axis with the onset of RBBB xs. Our results confirm Rosenbaum's contention that RBBB shifts the frontal plane QRS axis toward the right from above in a counterclockwise fashion is. In our study group, the initial rightward shift of the 20 msec QRS vectors noted in the frontal plane and associated 20-70 msec rightward deviation in the horizontal plane do not necessarily indicate that RBBB alters the initial 70 msec vectors when associated with LAHB, since these latter observations can be explained on the basis of

the types of loops recorded. Fifteen of 28 patients had 80% of their QRS loop directed anteriorly in the horizontal plane. Ten of these subjects had either Type II or III loops, and the presence of these configurations has been noted before in patients with right bundle branch block in the absence of LAHBem. It has been noted that, in the presence of LAHB and RBBB, there may be small Q waves present in scalar leads V2-Vs. These negative deflections are apparently due to early activation of the posterior left ventricular wall 18. Small (less than 0.10 mv) right precordial electrocardiographic Q "waves, suggesting the diagnosis of possible old anterior wall infarction, were present in nine of our 28 cases. Using the Frank vectorcardiogram, only a single patient showed posteriorly directed initial 20 msec QRS vectors in the horizontal plane, and she had a documented anterior wall myocardial infarction. Therefore, it is possible that the Frank vectorcardiogram may be a useful technique for assessing the importance of these small Q waves. This possibility warrants future investigation. Eight cases in our study group had vectorcardiographic evidence of inferior wall myocardial infarction in the presence of LAHB and RBBB. This incidence is of interest and indicates the variability of infarction site in relation to LAHB and RBBB. In fact, this association with inferior wall infarction is not rare; but, since the presence of small initial R waves in leads II, III, and aVF of the standard electrocardiogram may obscure the diagnosis of diaphragmatic wall infarction is, the vectorcardiogram is a superior technique for the diagnosis of these coexisting abnormalities a~,ln. Rosenbaum has stated that although inferior wall myocardial infarction may simulate LAHB, the diagnoses are not mutually exclusiveis, especially in presence of permanent Q-S waves in leads II, III, and aVF of the electrocardiogram. Our results confirm this proposal and demonstrate the advantage of being able to assess the initial forces with greater refinement, especially when dealing with the previously mentioned initial R waves in the inferior scalar leads. J. ELECTRCCARDIOLOGY,

V O L . 4, N O . 4 , 1971

VCG IN LAHB WITH R B B B

329

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Fig. 7. Vectorcardiogram and electrocardiogram from a 69 year old woman with coronary. artery disease and past history of myocardial infarction. The electrocardiogram shows sinus rhythm, prolonged P-R interval, LAHB with no S wave in lead I and small R and deep S waves in leads II and I I I ("standard masquerading BBB"), with a tall R wave in V 6 ("precordial masquerading BBB"), RBBB, and anteroseptal infarction. The vectorcardiogram shows LAHB, RBBB and initial 20 msec QRS vectors directed posteriorly m a counterclockwise fashion in the horizontal plane, indicating anteroseptal myocardial infarction. T h e most c o m m o n diagnosis ( 5 0 % ) in our study group was coronary artery disease, a n d the m e a n age of the patients was 65 years. These latter observations are consistent with previous studies concerning the etiology a n d age group of patients with c o m b i n e d L A H B a n d RBBB ls,1~ Eight of our cases h a d no historical or clinical evidence of a definite cause for their L A H B a n d RBBB. This is compatible with evidence linking "idiop a t h i c " degenerative calcific fibrotic c a r d i a c lesions with this conduction a b n o r m a l i t y 2~ I n conclusion, the following criteria a p p e a r to be most useful for the vectorcardiographic diagnosis of L A H B in the presence of RBBB: Superior displacement a n d counterclockwise inscription of the frontal p l a n e Q R S loop, a n d Q R S d u r a t i o n of 120 msec or m o r e with J. ELECTROCARDIOLOGY. VOL. 4, NO. 4. 1971

delayed inscription of the terminal 60 msec vectors. Acknowledgements: We wish to acknowledge the technical assistance of Frances Hernandez, Gall Hopper, Larry Kuriger, Sharleen Lucas, Deanna Moeller and Sydney Peebles.

1. 2. 3. 4. 5.

REFERENCES Rosenbaum, M. B., Elizari, M. V., and Lazzari, J. O.: Los Hemibloqueos, Buenos Aires, Paidos, 1968. Lenegre, J. : Etiology and pathology of bilateral bundle branch block in relation to complete heart block. Progr. Cardiov. Dis. 6:409, 1964. Lev, M.: Anatomic basis for atrioventrlcular block. Am. J. Med. 37:742, 1964. Rosenbaum, M. B.: Types of left bundle branch block and their clinical significance. J. Electrocardiol. 2:197, 1969. Castellanos, A., Jr., Lemberg, L., Ioannides, G., and Salhanick, L.: The vectorcardiogram in

3.30

6. 7. 8.

9.

10. 11.

12.

13.

B E N C H I M O L ET AL

right bundle branch block coexisting with left ventricular focal block. Am. J. Cardiol. ! 8:705, 1966. Chou, T. C., and Helm, R. A. : Clinical vectorcardiography. New York, Grune and Stratton, 1967. Saltzman, P., Linn, H., and Pick, A.: Right bundle-branch block with left axis deviation. Brit. Heart J. 28:703, 1966. Kulbertus, H., Collignon, P., and Humblet, L.: Vectorcardiographic study of QRS loop in patients with left superior axis deviation and right bundle-branch block. Brit. Heart J. 32:386, 1970. Benchimol, A., Barreto, E. C., and Pedraza, A.: The Frank vectorcardiogram in left anterior hemiblock. J. Electrocardiol. 4:116, 1971. Frank, E.: An accurate, clinically practical system for spatial vectorcardiography. Circulation 13:737, 1956. Langner, P. H., Okada, R. H., Moore, S. R., and Fies, H. L.: Comparison of four orthogonal systems of vectorcardiography. Circulation !1:46, 1958. Selvester, R. H., Haywood, L. J., and Griggs, D. E.: The timed vectorcardiogram: A useful clinical tool (as applied to the study of 1,500 subjects). Dis. Chest. 47:170, 1965. Benchimol, A., and Pedraza, A.: The timed vectorcardiogram in the diagnosis of cardiac

arrhythmias. J. Electrocardiol. 2:363, 1969 14. Benchimol, A., and Barreto, E. C.: Serial vectorcardiograms with the Frank system in patients with acute inferior wall myocardial infarction. J. Electrocardiol. 2:159, 1969. 15. Desser, K. B.,-and Benchimol, A. : Coexisting left anterior hemiblock and inferior wall myocardial infarction. Abstract. Clin. Res. 19:112, 1971. 16. Benehimol, A., and Desser, K. B.: Coexisting left anterior hemiblock and inferior wall infarction-vectorcardiographic features. Am. J. Cardiol. Accepted for publication. 17. Baydar, I. D., Walsh, T. J., and Massie, E.: A vectorcardiographic study of fight bundle branch block with the Frank lead system. Clinical correlation in ventrieular hypertrophy and chronic pulmonary disease. Am. J. Cardiol. ]$:185, 1965. 18. Rosenbaum, M. B., Elizari, M. V., and Lazzari, J. O.: The hemiblocks. Florida, Tampa Tracings, pp. 97-137, 1970. 19. Watt, T. B., Jr., and Pruitt, R. D.: Character, cause, and consequence of combined left axis deviation and right bundle branch block in human electrocardiograms. Am. Heart J. 71:460, 1969. 20. Rosenbaum, M. B., Elizari, M. V., Kretz, A., and Taratuto, A. L.: Anatomic basis of A-V conduction disturbances, Geriatrics 25:132, 1970.

J. ELEETRCICARDIOLOGY. VOL. 4. NO. 4. 1971