Electrophysiological and Histological Correlations

in Two Cases of Complete Heart Block

Shin-ichiro OHKAWA, M.D., Satoru MATSUSHITA, M.D., Keiji UEDA, M.D., Hiroshi MATSUO, M.D.,*

and Masaya SUGIURA, M.D.

SUMMARY

Electrophysiological and histological correlation was documented in 2 cases of complete heart block (CHB).

Case 1 (77 yrs. female): CHB continued for 1.5 years with nor-mal QRS in axis and duration. The His bundle electrogram (HBE) showed A-H block with normal H-V interval (40 msec). Ten months later she died of bronchopneumonia and paralytic ileus. Histological study of the conduction system revealed a giant nodule of calcification in the mitral ring and central fibrous body, which compressed the end of the A-V node and most part of the penetrating portion of the A-V bun-dle. Above-mentioned findings were thought to be compatible with A-H block in HBE.

Case 2 (82 yrs. male): His EGG showed CHB with QRS configura-tion of right bundle branch block (RBBB) with left axis deviation (LAD), with transient appearance of RBBB with right axis deviation (RAD) or left bundle branch block (LBBB) patterns. The HBE revealed normal PH interval (120 msec), and the site of block was distal to the A-V bun-dle. In addition to the H potential, spike 'X' was also recorded 20 msec before QRS wave. He died suddenly after 1.5 years of hospitalization. Histological examination revealed that both anterior and posterior fascicles of the left bundle branch showed severe destruction at their origins, and the right bundle branch also showed marked fibrosis. These histological

fi ndings were so-called ` 'trifascicular block' and compatible with H-V block in HBE. And the meaning of the 'X' spike in HBE was dis-cussed.

Additional Indexing Words:Complete heart block His bundle electrogram A-H block H-V block Mitral ring calcification Trifascicular block

RECENT development of clinical application of His bundle electrography

has been making it possible to interpret various degrees of atrio-

From the Department of Internal Medicine, Tokyo Metropolitan Geriatric Hospital (Yoiku-in) , Itabashi-ku, Tokyo 173 (Requests for reprints).

The Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo. Received for publication May 20, 1976.

287

288 OHKAWA, MATSUSHITA, UEDA, MATSUO, AND SUGIURA Jap. Heart J. May, 1977

ventricular (AV) block with more accuracy. But there have been only a few cases, who were examined both by the HBE and the histological study of the conduction system1)-5). In this communication we reported 2 cases of CHB, one of whom showed A-H block and the other H-V block, and tried to correlate the electrophysiological and histological findings.

CASE REPORTS

Case 1: A 76-year-old female entered the hospital with chief complaints of edema and dyspnea. Her ECG showed normal sinus rhythm and no axis devia-tion at the age of 74 (Fig.1 a), and the ECG on admission showed complete heart block with ventricular rate of 40/min and QRS pattern of RBBB+RAD (Fig.1 b). Two weeks later QRS complex changed to the pattern of normal width with no axis deviation (Fig.1 c), which was a predominant pattern during her clinical course. Auscultation of the heart on admission revealed a systolic murmur (Grade 2/6) and canon sounds. Phonocardiogram confirmed these findings and further revealed a diastolic murmur (Fig.2). X-ray films of the chest revealed a calcifi-cation of mitral ring of ̀ 'J' shape and a cardio-thoracic ratio of 58%. Five months

Fig.1. Electrocardiograms of Case 1, a) taken at 74 years of age, show-ing normal sinus rhythm and no axis deviation, b) taken at 76 years of age, showing complete A-V block with a ventricular rate of 40/min and QRS pat-tern of RBBB+RAD, c) showing CHB with QRS pattern of normal width and no axis deviation, d) taken during Adams-Stokes' attack, showing a ven-tricular rate of 16/min, e) showing CHB with QRS pattern of LBBB, f) taken after the implantation of a permanent pacemaker, and g) showing normal sinus rhythm even after the implantation of a pacemaker.

Vol.18 No.3 PATHOLOGY OF HEART BLOCK 289

after admission she developed a syncope with heart rate of 16/min (Fig.1 d). Ad-ministration of isoproterenol and temporary pacing were effective for this episode. A bipolar electrode was inserted to the right heart and the HBE was recorded on the direct-writing recorder according to Scherlag's method6) (Nihonkoden recti-

graph RGJ 3004, electronic amplifier AVB-2 with a time constant of 3 msec and

Fig.2. Phonocardiogram of Case 1, showing ejection type systolic murmur (SM) and diastolic murmur (m) following atrial sound (A).

Fig.3. His bundle electrogram and its schema of Case 1, showing

A-H block with normal H-V interval.

290 OHKAWA, MATSUSHITA, UEDA, MATSUO, AND SUGIURA Jap. Heart J. May, 1977

paper speed 25-100mm/sec). Also 4-channel tape system was utilized for further analysis. H-V interval was 40 msec and A-H block was diagnosed (Fig.3). After 8 months a permanent pacemaker of demand type (Medtronic 5942) was implan-ted (Fig.1 f). But thereafter her ECG occasionally showed 2: 1 A-V block or nor-mal sinus rhythm (Fig.1 g). After 1 year and 5 months of CHB she suffered from bronchopneumonia and paralytic ileus, and died.

Autopsy showed the heart weight of 330Gm and moderate coronary sclerosis without myocardial infarction. The calcification of posterior mitral annulus was

f ound, which was spreading over the ventricular septum, proved by soft X-ray films

(Fig.4). The conduction system was examined as previously reported7) according to Lev's method.8) The end of A-V node was compressed by a large nodule of cal-cification encompassing from the summit of the ventricular septum to central fi-brous body (CFB) (Fig.5 a). The penetrating portion of A-V bundle was remark-ably compressed by this giant calcification of the septum (Fig.5 b), causing severe degeneration of conducting cells. The effect of calcification was slight in the bran-ching portion of A-V bundle, showing slight fibrosis. Left posterior fascicle of the left bundle branch was severely fibrotic (Fig.6 a) but lesion of the left anterior fas-cicle was slight. Right bundle branch revealed slight fibrosis in the first and second

portions but third portion of the right bundle branch was markedly interrupted by

Fig.4. Soft X-ray film of postmortem heart of Case 1, showing mitral ring calcification (MRC) and calcification of the top of the septum (arrows).

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PATHOLOGY OF HEART BLOCK 291

Fig.5. Case 1, a) the end of atrioventricular node (N) and b) the

penetrating portion of the A-V bundle (B), both compressed by giant nodule of calcification of ventricular septum (arrows).

292 OHKAWA, MATSUSHITA, UEDA, AND SUGIURA Jap. Heart J. May, 1977

Fig.7. Electrocardiograms of Case 2, a) taken at 81 years of age, show-ing CHB with QRS pattern of RBBB+LAD, b) showing CHB with QRS pat-tern of LBBB, c) showing 2: 1 A-V block with QRS pattern of RBBB+LAD, and d) taken at 82 years, showing CHB with QRS pattern of RBBB+LAD, when HBE was recorded.

subendocardial fibrosis and endocardial fibroelastosis of the right ventricle (Fig.

6 b).

Case 2: An 81-year-old male was admitted to the Yoiku-in Hospital with a

chief complaint of occasional exertional vertigo. He had never experienced any

syncopal attacks and at the age of 78 he was diagnosed to have hypertension.

Physical examination on admission revealed a well-developed aged man. The

blood pressure was 200/94mmHg, heart rate 42/min, which was CHB with QRS

pattern of RBBB+LAD in ECG (Fig.7 a). Laboratory data showed slight an-

emia, proteinuria and positive serological test for syphilis. The X-ray films of the

chest had no signs of congestion with cardio-thoracic ratio of 58%. The cardiac

index was 2.40L/min/M2 by the dye dilution method. Treatment was done by

antihypertensive drugs and ƒÀ-stimulating agent. Two weeks after admission he

had bronchopneumonia, when his ECG showed transient 2: 1 A-V block (Fig.7 c).

About a half year later the blood pressure was maintained at the level of 150/

•© Fig.6 (opposite page). Case 1, a) the posterior fascicle of the left bundle

branch, revealing complete interruption of conducting cells by fibrosis

(arrows) and b) the third portion of the right bundle branch, showing

disappearance of conducting cells by subendocardial fibrosis and endocardial

fi broelastosis of the right ventricle (arrows).

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Fig.8. His bundle electrogram of Case 2, showing PH interval of 120 msec and besides H potential 'X' spike was recorded (XQ interval: 20 msec).

70mmHg. At the age of 82, the HBE revealed normal PH interval (120 msec) and another spike (X) with 20 msec before QRS wave (Fig.8). The site of block was diagnosed to be distal to A-V bundle. After 35 days from the recording of HBE he died unexpectedly.

Autopsy was performed. The heart weight was 400Gm with hypertrophy of the left ventricle. Coronary arteries showed moderate sclerosis, but there were no

Fig.9. Case 2, the penetrating portion of A-V bundle, revealing about 50% replacement of conducting cells by the fatty tissue.

294 OHKAWA, MATSUSHITA, UEDA, MATSUO, AND SUGIURA Jap. Heart J. May, 1977

Fig.10. Case 2, branching portion of A-V bundle (B) was almost intact but a) the posterior fascicle and b) the anterior fascicle of the left bundle branch disclosed complete interruption of the conducting cells by marked

fi brosis (arrows).

abnormalities in the valves. Histological examination revealed scattered myocar-dial fibrosis but no infarction. The study of the conduction system showed that the S-A node and A-V node were almost intact, with patency of S-A nodal and A-V nodal arteries despite of moderate sclerosis of main coronary arteries. The lower

part of penetrating portion of A-V bundle was replaced by fatty tissue in almost 50% (Fig.9). The branching portion of A-V bundle itself showed moderate changes. Both anterior and posterior fascicles of the left bundle branch revealed complete interruptions of the conducting cells, which were localized in the proximal

portion of the left bundle branch (Fig.10 a, b). The right bundle branch showed fi brotic changes in the terminal half of the first portion and the entire second por-tion (Fig.11 a, b).

DISCUSSION

The histological studies of A-V block have been accumulated since the

works by Yater,9) Lev,10) and Lenegre.11) We have also reported the his-

tological studies of the conduction system with various conduction distur-

bances.7),12)-14) In these works the principal sites of lesions in chronic A-V

block have been demonstrated in the branching portion of the A-V bundle

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Fig.11. Case 2, right bundle branch, a) the first portion, showing marked fibrosis and b) the second portion revealing complete disappearance of conducting cells (arrows).

including the beginning of the bundle branches. Despite of newly acquired informations on the A-V block by the His bundle electrograms, there have been only sporadic reports on the comparison of the findings of HBE and of the histology of the conduction system. Rosen, Lev et al1)-4) have re-

ported 10 cases from the view point of these correlations. They demonstrated that A-H block was induced by the lesion of the A-V node and its approaches and H-V block resulted from the lesions of the bundle branches. Hunt et al5) reported 7 cases of heart block complicating acute myocardial infarction, which showed a good correlation between the changes in HBE and histology.

In our 2 cases A-H block in the first case was induced by the lesions of lower part of the A-V node and the penetrating portion of the A-V bundle due to compression by a giant mass of calcification in the ventricular septum and central fibrous body. Remaining cells of penetrating portion of the A-V bundle with degeneration might explain that the case transiently showed nor-mal sinus rhythm. Some cases of CHB were believed to be induced by calcification of central fibrous body and/or septal summit as reported by Naga-

yo,15) Yater,9) and Korn et al.16) We previously reported a case of CHB with atrial flutter, resulting from the similar calcification.17) As in this first

296 OHKAWA, MATSUSHITA, UEDA, MATSUO, AND SUGIURA Jap. Heart J. May, 1977

case heart block induced by mitral ring calcification and its involvement of septal summit and complicated apical diastolic murmur was called Rytand's syndrome.18).19) Calcified lesions of the A-V bundle resulted in split His bundle potentials in 2 cases of Bharati et al.4) Marked difference from our case was the localization of the calcification. In our case it extended from the A-V node to the almost whole penetrating portion of the A-V bundle

(A-H block), while the case of Bharati showed localized calcification, leaving intact portions at both the proximal and distal A-V bundle.

In the second case (H-V block) the site of block was located in the be-

ginning of bundle branches, which might be attributed to pathological 'tri-fascicular block' postulated by Rosenbaum.20) We previously reported21) a typical case of 'trifascicular block' and correlated the electrocardiographic changes and the histology of the conduction system. In the case presented here there was another spike ('X' spike) in addition to the H potential in the HBE. This apparently suggested 'block within His bundle'.22) But, since the interval of X-Q was too short for the potential originating from His bundle and the histological study showed an incomplete lesions (about 50%) in the lower penetrating portion of A-V bundle, intra-His block seems unlikely. Although the configuration of QRS on a surface electrocardiogram was RBBB+RAD pattern, it is not ruled out that the spike 'X' might be the potential of probably the remaining first portion of the right bundle branch. However, almost complete interruption at the second portion of the right bundle branch seems to be a difficulty for this explanation. It may reflect a retro-

grade excitation of the A-V bundle evoked by the anterior fascicle of the left bundle. But from the histological changes of the conduction system such hypothesis may be difficult. Although the potential of the left bundle branch has never been recorded by the right heart catheterization, the 'X' spike may be a potential of left bundle branch itself, because the length of complete interruption of the left bundle branch was short and the remaining

peripheral fascicles were large and intact and because the interval of X-Q is compatible with that reported by Rosen23) on the left bundle potential.

Our study disclosed that the A-H block on HBE indicated the sites of block in not only the A-V node but also in the penetrating portion of the A-V bundle in so far as the lesions continued from the A-V node. Also the lesions in branching portion of the A-V bundle might result in H-V block in so far as the lesions continued to the beginning of both bundle branches. There must be an accumulation of cases to conclude the sites of block from the HBE.

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