Long-term prognosis after acute anterior infarction with atrioventricular block.

The purpose of this study was to evaluate the need for permanent pacing in patients who have survived the effects of anterior myocardial infarction with complete heart block and have returned to sinus rhythm but who are left with impairment of intraventricular conduction. We have reviewed 52 patients with complete heart block complicating recent anterior myocardial infarction. Temporary pacing was instituted in all patients. There were 25 hospital survivors who were followed for an average of 49 months. Long-term pacing was established in 4 patients. Of the 21 patients in sinus rhythm, 14 had partial bilateral bundle-branch block with either right bundle-branch block and left anterior hemiblock or right bundle-branch block and left posterior hemiblock; at the end of the follow-up period, 10 of these 14 were alive and well. Furthermore, permanent pacing failed to prevent sudden death in 2 patients. At the present time, therefore, we conclude that long-term pacing is not justified in patients, otherwise asymptomatic, with partial bilateral bundle-branch block persisting after transient complete heart block in anterior myocardial infarction.     

The fate of patients with intraventricular conduction disturbances complicating acute myocardial infarction.

The partial incidence and the early and late mortality were studied in 104 patients with acute myocardial infarction complicated by intraventricular conduction defects. Right bundle branch block and left anterior hemiblock had a greater incidence than the other conduction anomalies, while the hospital mortality was greater for the complete right bundle branch block combined with left anterior or posterior hemiblock, followed in order by complete left bundle branch block. Late morality was higher in cases with complete right bundle branch block combined with left posterior hemiblock and also in cases with focal block or left bundle branch block indicating a poor prognosis for these patients. For the rest sub-groups of patients late mortality was relatively low indicating the possibility of long survival after passing the acute phase. However, longer periods of observation are desirable for further estimation of their ultimate prognosis.     

Natural history of combined right bundle branch block and left anterior hemiblock (bilateral bundle branch block)

One hundred fifteen patients with combined right bundle branch block (RBBB) and left anterior hemiblock (LAH) were separated into two groups depending upon whether RBBB and LAH was associated with acute myocardial infarction (group I, 32 patients) or was a chance electrocardiographic finding (group II, 83 patients).In 10 patients in group I complete heart block developed and in six patients high grade second degree atrioventricular (A-V) block developed. The incidence of serious arrhythmia was twice and mortality was three times the average for the coronary care unit (CCU).The majority of patients in group II had clinical evidence of advanced myocardial disease as manifested by congestive heart failure, healed myocardial infarction and left ventricular dyskinesia. During a cumulative observation period of 262 patient years, complete heart block developed in only two patients, whereas second-degree A-V block of sufficiently high degree to necessitate permanent cardiac pacing developed in three patients.It is concluded that (1) combined RBBB and LAH usually reflects advanced myocardial disease, (2) the clinical course is determined more by the myocardial disease than by the conduction disorder, (3) prophylactic cardiac pacing is not warranted in chronic RBBB and LAH, and (4) cardiac pacing has little impact on mortality when RBBB and LAH are associated with acute myocardial infarction.     

The clinical features and significance of bifascicular block complicating acute myocardial infarction.

Two series of patients with anterior myocardial infarction complicated by right bundle branch block with either left anterior hemiblock (RBBB+LAH) or left posterior hemiblock (RBBB+LPH), have been studied. The first was a retrospective analysis taken from a time when prophylactic pacing wires were not inserted, and the second was a prospective series in whom pacing wires were inserted as soon as the condition defect was seen. The overall prevalence of RBBB+LAH was 3.3% compared to 1.6% for RBBB+LPH, and complete atrioventricular block was seen in 36% of the former and 66% of the latter. From the retrospective data it was apparent that hospital death was usually associated with massive myocardial infarction, although 3 of the 25 patients in this series died in hospital from sudden development of complete atrioventricular block. If the defect was transitory (1-3 days) then the prognosis was that of acute anterior infarction uncomplicated by fascicular block. The policy of prophylactic pacing failed to show any overall change in hospital mortality, and only 3 patients survived long enough to have permanent pacemakers inserted. This procedure has been of benefit to only one of these cases.     

Mechanism and significance of widened QRS complexes during complete atrioventricular block in acute inferior myocardial infarction

Twelve of 35 consecutive patients admitted with complete, atrioventricular (A-V) block complicating acute inferior myocardial infarction manifested widened QRS complexes. The escape beats had the pattern of left bundle branch block in four patients, right bundle branch block in five patients and both left and right bundle branch block in three patients.

His bundle recordings in five patients with escape beats that had a left bundle branch block configuration revealed a His bundle potential preceding the widened QRS complex at His-V intervals of 45 to 60 msec. Bradycardia-dependent left bundle branch block was demonstrated in two patients by His bundle pacing. In three patients the conducted beats had a left bundle branch block configuration after critical lengthening of the R-R interval during second degree A-V block before or after the episode of complete A-V block. In six patients whose escape beats had a right bundle branch block configuration, His bundle recordings did not reveal a His bundle potential preceding these beats.

Our observations suggest that widened QRS complexes with a left bundle branch block configuration could be due to an A-V junctional escape rhythm with phase 4 left bundle branch block. Alternatively in association with a right bundle branch block configuration it is possible that the widened QRS complexes represent a ventricular or fascicular escape rhythm.

Two of 12 patients with widened QRS complexes died. There were no significant differences in immediate mortality, 6 month mortality or mean peak serum glutamic oxaloacetic transaminase (SGOT) values between patients with narrow and widened QRS complexes. This finding suggests that widened QRS complexes during complete A-V block in acute inferior myocardial infarction have no prognostic significance.     

The incidence and mortality of intraventricular conduction defects in acute myocardial infarction

The incidence of intraventricular conduction defects during sinus mechanism was 24 percent in 212 consecutive cases of acute myocardial infarction observed in a coronary care unit. Patients with intraventricular conduction defects had a higher mean age than that for the entire series (P < 0.01), and death occurred at a younger age than in patients without such defects (P < 0.1). The most common isolated defect was left anterior hemiblock (incidence of 9.4 percent). The next most common conduction defect was incomplete bilateral bundle branch block (incidence 7.5 percent); more than half of these patients had right bundle branch block with left anterior hemiblock. Far less frequent were isolated complete right bundle branch block and complete left bundle branch block. Left posterior hemiblock was rare and was not seen in patients without other intraventricular conduction defects either transient or permanent. The hospital mortality rate of the entire series was 21.2 percent. The mortality rate among patients with intraventricular conduction defects was 47 percent which is significantly different from that for the entire series (P < 0.01) and from a series matched by sex and age (P < 0.01). The most innocuous intraventricular conduction defect was left anterior hemiblock (in-hospital mortality rate 25 percent). This was statistically not different from the mortality rate in the total series. Higher mortality rates were associated with other conduction defects which produced QRS prolongation and bifascicular block.     

Bundle branch blocks and/or hemiblocks complicating acute myocardial ischemia or infarction

Despite the bulk of anatomical and histologic evidence supporting the existence of three fascicules in the left branch of the His bundle, the concept of a bifascicular system proposed by Rosenbaum and his school has been adopted by the cardiological community as a practical teaching tool. Left anterior hemiblock (LAH) refers to block of the antero-superior branch of the left branch which is small and left posterior hemiblock (LPH) to block of the postero-inferior branch which is larger. The LAH is more common that the LPH and often associated with a complete right bundle branch block (RBBB). Coronary artery disease (CAD) is a major cause of hemiblocks. In this review article, we discuss various aspects of the relation of hemiblocks with CAD. We looked at the prevalence of LAH in consecutive patients undergoing coronary angiography and who had a significant coronary lesion in one vessel or more. In all patients with LAH, a significant lesion of the left anterior descending coronary artery was present, with in the majority of patients, an impairment of the left ventricular function. Bifascicular block (RBBB with LAH or LPH) can complicate acute myocardial infarction and is often associated with a poor prognosis and the presence of heart failure. Thrombolysis and or early angioplasty in acute myocardial infarction have significantly improved the prognosis and reduced the mortality associated with bifascicular block. Left anterior hemiblock pattern was also observed during angina pectoris occurring at rest or induced by exercise or atrial pacing. In these circumstances, LAH is transient and is likely to be due to ischemia in the anterolateral wall related to a lesion of the main trunk or the proximal left anterior descending coronary artery with the postero-inferior wall being first depolarized. The presence of bifascicular block in acute myocardial infarction still is associated with an unfavorable prognosis as compared to non-bundle branch block patients because of the common association with heart failure and other comorbidities.     

Bradyarrhythmias, abnormalities of conduction, and indications for pacing in acute myocardial infarction

Bradyarrhythmias and conduction disturbances are not infrequently observed in association with acute MI. The sinus node artery is supplied by the right coronary circulation only slightly more often than the left. As a result of concomitant vagotonia, however, sinus node dysfunction is more common with inferior infarction. This influence, as well as a predominantly right-sided circulation, also makes AV nodal block more frequent with such infarctions. Bradyarrhythmias due to sinus or AV nodal dysfunction often require only observation. If symptomatic, they are usually responsive to vagolytic or chronotropic drugs, but may necessitate pacemaker therapy often only on a temporary basis. The distal conduction system including the bundle branches is supplied mainly, but not exclusively, by the left anterior descending artery. Thus, acute bundle branch block is often associated with anterior MI. The indications for both temporary and permanent prophylactic pacing in this situation remain controversial. Several authors have made recommendations based on risk stratification. We would temporarily pace patients with anterior or indeterminate infarctions and new right or left bundle branch block, and probably those with bilateral bundle branch block of indeterminate age. All patients with new bilateral or alternating bundle branch block should be paced, regardless of infarct site. Permanent prophylactic pacing would appear indicated in patients exhibiting alternating bundle branch block or perhaps new right bundle branch block and left posterior hemiblock. In contrast to this group, the treatment of patients who develop sudden complete heart block, whether transient or permanent, is clear-cut. These patients require continuous (temporary followed without interruption by permanent) pacemaker therapy (Table 3).     

Fascicular conduction distrubances after coronary bypass surgery.

Two hundred patients underogoing coronary bypass graft surgery were studied to determine the frequency and significance fo new fascicular conduction distrubances. The follow-up period ranged from 13 to 39 months. New disturbances developed in 39 patients (20 percent). Isolated right bundle branch block (6 percent) and left anterior hemiblock (6 percent) were the most common disturbances. Righ bundle branch block was usually transient and was not associated with further complications in the follow-up period. However, patients with either transient or persistent left bundle branch block or left anterior hemiblock, or both, had (1) increased later mortality compared with patients without new fascicular conduction disturbances (5 of 26 versus 11 of 161; P less than 0.02), and (2) increased late myocardial infarction (2 of 26 versus 2 of 161; P less than 0.05). New left fascicular conduction disturbances after coronary surgery identified a subset of patients with more extensive ischemic heart disease, suggesting that these patients require close follow-up care.     

Long-term prognosis in patients with bundle branch block complicating acute anteroseptal infarction

In a previous study patients with bundle branch block complicating acute anteroseptal infarction were found to have a high incidence rate of sudden death and late ventricular fibrillation in the first 6 weeks after infarction. Forty-two such consecutive patients were therefore kept within the monitoring area during those 6 weeks. Eighteen (43 percent) of these 42 patients survived and were then followed up for an average of 13 months to assess long-term prognosis and to evaluate whether the in-hospital monitoring period should be extended over 6 weeks. In most of these 18 patients a bifascicular block developed in the acute stage of infarction and in 3 it progressed to transient high degree atrioventricular (A-V) block. Seven of the 18 survivors had potentially lethal complications during the first 6 weeks. Four of these seven underwent aneurysmectomy between 10 and 20 weeks after infarction, and one of them died of a surgical complication. Major cardiac events occurred in 3 of the 17 survivors. None of these patients died during the follow-up period. In one patient complete A-V block developed after aneurysm resection; this was the only patient treated with permanent pacing. Fifteen of the 17 patients were in functional class I or II.These results indicate that (1) patients with bundle branch block complicating acute anteroseptal infarction who survive the first 6 weeks after infarction have a good prognosis during the 1st year, and (2) extension of the in-hospital monitoring period is not necessary. The results further suggest that prophylactic permanent pacing does not affect prognosis in these patients.     

Atrioventricular and intraventricular conduction in hyperkalemia

Twelve patients exhibited electrocardiographic evidence of fascicular block during hyperkalemia. Isolated left posterior hemiblock occurred in four, isolated left anterior hemiblock in two, right bundle branch block with left anterior hemiblock in two, right bundle branch block with left posterior hemiblock in one, left bundle branch block with abnormal left axis deviation in two and advanced atrioventricular block in one. In all seven patients with sinus rhythm the P-R interval shortened after correction of hyperkalemia. Electrophysiologic studies using His bundle recording and atrial pacing in one patient revealed intraatrial conduction delay and marked prolongation of conduction time in the His-Purkinje system. It is concluded that conduction defects in the specialized intraventricular conduction system are common in hyperkalemia and result in electrocardiographic patterns of fascicular block.     

Ischemia-associated intraventricular conduction disturbances during exercise testing as a predictor of proximal left anterior descending coronary artery disease

To determine the incidence and significance of transient intraventricular conduction abnormalities occurring in association with myocardial ischemia during exercise testing, the recordings of 2,200 consecutive exercise tests were reviewed. Ten patients (0.45%) were identified as having both ischemia and intraventricular conduction abnormalities that developed transiently during the exercise test. In all 10 patients both typical angina and electrocardiographic evidence of ischemia developed during exercise. Among the 10 patients, left anterior hemiblock developed in 4, left posterior hemiblock in 2, right bundle branch block (RBBB) in 2, RBBB with left axis deviation in 1, and left anterior hemiblock progressing to complete left bundle branch block (LBBB) in 1. All 10 patients had cardiac catheterization showing significant obstruction of the left anterior descending (LAD) coronary artery at or before the origin of the first septal branch. Eight patients were treated surgically and 2 medically, all with relief of ischemic symptoms. Nine of the 10 had repeat exercise stress testing without angina or electrocardiographic evidence of ischemia and without recurrence of the transient intraventricular conduction disturbance.It is concluded that the development of transient intraventricular conduction abnormalities associated with myocardial ischemia during exercise testing is an uncommon occurrence (0.45%). When such conduction disturbances do develop, the existence of significant disease in the proximal portion of the LAD coronary artery is strongly suggested. With control of myocardial ischemia, the transient conduction disturbances during exercise are ameliorated.     

Atrioventricular block with lidocaine therapy

A case is presented of complete atrioventricular (A-V) block occurring after a 50 mg bolus injection of lidocaine. Base-line studies before administration of lidocaine showed evidence of trifascicular block manifested by complete right bundle branch block, left anterior hemiblock and a markedly prolonged H-V interval. Advanced A-V block and then complete A-V block distal to the His bundle developed after administration of lidocaine. Lidocaine should be used with caution in patients with trifascicular disease; if it is administered to such patients, insertion of a temporary pacemaker catheter should be considered.     

Conduction defects in acute myocardial infarction in the Chinese in Hong Kong

In order to delineate the conduction defects complicating acute myocardial infarction in the Chinese, 636 Chinese patients admitted into one of the three medical units of a general hospital in Hong Kong in the period 1973-80 were reviewed. A relatively high incidence of conduction defects was observed, including atrioventricular block (11.3%), right bundle branch block (12.7%) and left bundle branch block (3.3%). Right bundle branch block (whether isolated or combined with left fascicular block) and atrioventricular block complicating anterior Q-wave infarction were ominous, with a high incidence of pump failure, cardiogenic shock and cardiac arrhythmias. These are markers of massive infarction. Atrioventricular and bundle branch blocks complicating inferior Q-wave infarction were benign. Left bundle branch block appeared to be a more chronic lesion, with moderate mortality, and isolated left anterior hemiblock did not adversely affect the short-term outcome. These results conform well to the patterns seen in Western series. The high incidence of conduction defects, in particular right bundle branch block and atrioventricular block complicating anteroseptal infarction, indicates a more serious clinical spectrum of acute myocardial infarction in the Chinese, and could have contributed to a higher hospital mortality in the Chinese series.     

Studies of acute myocardial infarction with intermittent bundle branch and hemiblock

Two cases of transient hemiblock occurring during the course of acute myocardial infarction are reported. The transient manifestation permits the accurate evaluation of the diagnostic features of the hemiblocks as modified by acute infarction. One case reflects the development of left bundle branch block due to bilateral post-divisional block which inter alia permits the study of left bundle branch block in the presence of acute myocardial infarction.     

The significance of bundle branch block during acute myocardial infarction.

Analysis of the course of 71 patients with acute myocardial infarction complicated by bundle branch block (BBB) confirms a high incidence of atrioventricular (A-V) block (42 per cent) and severe pump failure (35 per cent) in these patients. Hospital mortality was not correlated with BBB per se, but rather with the associated development of second or third degree A-V block (57 per cent with A-V block vs. 12 per cent without A-V block; p less than .0005) or severe pump failure (35 per cent with vs. 11 per cent without severe pump failure; p less than .001). However, late mortality was high and not significantly different among those surviving hospitalization whether transient A-V block was present or absent. Eight of 11 late deaths were sudden. Temporary pacing could not be shown to alter hospital survival statistically, but made the onset of complete heart block a hemodynamically smooth and clinically undetectable event in several patients who later survived. The place of permanent pacing in these patients cannot be clearly determined on the basis of this study or in the available literature. More data obtained either by pooling the experience of several centers or from a prospective randomized study are needed to determine the indications for permanent pacemakers.     

Pictures of the fascicular block inacute myocardial infarct with special reference to left anterior hemiblock and the bifascicular block of the anterior type]

In the etiology of uni, bi- and trifascicular block pictures the acute myocardial infarction plays an important role. From the topographic relations of the supply of coronary vessels to the coduction system certain correlations between localisation of infarction and kind of blocking are to be explained. The electrocardiographic changes of the individual block pictures are explained. 765 (581 males, 184 females) patients with acute myocardial infarction were examined concerning frequency and prognosis of the left anterior hemiblock and the bifascular block of anterior type (left anterior hemiblock, right bundle branch block). A left anterior hemiblock could be proved in 90 cases (11.8%), a bifascicular block of anterior type in 38 cases (5%). With 30% the lethality of the first group was not essentially above the lethality of patients with infarction without block pictures (29.6%). In patients with bifascicular block of anterior type it was significantly incrased with 68.4%. The two block forms were nearly exclusively found in the anterior wall infarction and its combination with a posterior wall infarction, respectively. 11 patients, out of whom 9 died, showed a transition of the bifascicular block into a trifascicular one. In 6 cases a left anterior hemiblock had preceded. The results concerning frequency and prognosis much correspond with the reports of other authors. In the bifascicular block, apart from the danger of a sudden asystolia, also the most cases larger size of the extension of the infarction with the adequately higher risk of a muscular insuficiency might be responsible for the bad prognosis. The therapeutic possibilities and necessities deriving from this are explained.     

Chronic right bundle branch block and left posterior hemiblock: Clinical, electrophysiologic and prognostic observations

Twenty-one patients with long-term right bundle branch block and left posterior hemiblock were studied electrophysiologically and then followed up prospectively. The group consisted of 19 men and 2 women aged 61 ± 2.7 years (mean ± standard error of the mean). The majority of patients had either hypertensive cardiovascular disease (48 percent) or primary conduction disease (33 percent). Initial electrophysiologic studies revealed A-H intervals of 58 to 152 msec (mean 98 ±7.7) and H-V intervals of 40 to 80 msec (mean 52 ± 2.1). Six patients (29 percent) had prolonged H-V intervals. The follow-up period ranged from 91 to 1,231 days (mean 671 ± 68). Three of 21 patients (14 percent) needed a permanent pacemaker after development of the following symptomatic conduction disease: sinoatrial block on day 3 of follow-up; second degree atrioventricular (A-V) block, site undetermined, on day 118; and second degree A-V block proximal to the His bundle on day 398. One patient died suddenly (on day 571), and two others died of noncardiac causes.

In conclusion, combined right bundle branch block and left posterior hemiblock was associated with less trifascicular disease than reported previously. The clinical course of most of the patients was benign and the incidence of sudden death was relatively small. Symptomatic conduction disease occurred but could be definitely related to trifascicular disease in only one patient. These short-term data suggest that prophylactic pacemaker insertion is not routinely indicated in patients with chronic right bundle branch block and left posterior hemiblock.     

Smoldering myocarditis with intermittent complete A-V block and Stokes-Adams syndrome A histopathologic and electrocardiographic study of “trifascicular” bundle branch block

This is a clinicopathologic study of a 46 year old woman with smoldering chronic idiopathic myocarditis and intermittent complete atrioventricular (A-V) block. Her electrocardiograms showed left posterior hemiblock, complete right bundle branch with 2:1 A-V heart block, and eventually complete A-V heart block due to bilateral or “trifascicular” bundle branch block. The pathologic examination revealed organizing myocarditis with fibrosis of the summit of the ventricular septum, associated with severe old destruction of the origin of the left bundle branch, more recent partial destruction of the right bundle branch, and acute degeneration and inflammatory changes mostly of the branching portion of the A-V bundle, the bifurcation and both bundle branches.     

Prognostic Factors in Atrioventricular Block Complicating Acute Myocardial Infarction

Summary: Atrioventricular block (A-V block) was documented in 150 (13.8%) of 1083 patients with acute myocardial infarction. Those with A-V block differed significantly from the remainder, being older, having higher peak levels of serum lactic dehydrogenase and a greater incidence of left ventricular failure and of death in hospital.
These differences were due mainly to the inclusion of 90 patients with complete heart block (CHB). Among those patients whose CHB complicated anterior infarction there was a significantly greater incidence of previous infarction.
Lesser grades of A-V block and right bundle branch block (RBBB) commonly heralded the onset of CHB, which occurred more frequently in those with inferior infarction.
Markers of death in those with CHB were anterior infarction, RBBB, and a slow subsidiary pacemaker with a wide ventricular complex. Pacing is recommended for all patients with CHB and for those with RBBB; the reasons for this are presented in detail.