Long-term survival of patients with incomplete bundle-branch block complicating acute myocardial infarction

Clinical and electrophysiologic findings in acute ischemic intraHisian bundle-branch block

Clinical and electrophysiologic features of acute ischemic right bundle-branch block (RBBB) that are reversible by His bundle pacing were analyzed in nine patients. All had large anterior myocardial infarctions (mean peak CK-MB = 185 +/- 71 IU/l), and six showed increased pulmonary capillary pressures. The RBBB occurred within 48 hours of infarction, and in six patients it was associated with left fascicular block. The HV intervals that were measured 1 to 4 days after infarction were normal in all patients. Progression to complete atrioventricular (AV) block occurred in three patients, and one patient required permanent cardiac pacing. Sustained ventricular tachycardia developed in two patients, and ventricular fibrillation developed in five. During a mean follow-up period of 26 months, four patients died (three of them suddenly). The RBBB disappeared in only one case. Acute ischemic intraHisian RBBB occurred in the setting of massive myocardial infarctions complicated by ventricular tachycardia or fibrillation and by a high mortality rate during the follow-up period. The RBBB rarely reverted spontaneously, and the His-Purkinje conduction time was frequently normal.

Long-term prognostic significance and electrophysiological evolution of intraventricular conduction disturbances complicating acute myocardial infarction

Fifty-nine patients with post-infarctional, isolated intraventricular conduction disturbances (IVCD) who survived the acute stage of myocardial infarction were followed up after hospital discharge for a mean period of 11.4 +/- 4.8 months. Fourteen patients (24%) had HV interval prolongation (greater than 55 ms) during AMI (group A), and 45 patients had normal HV intervals (76%, group B). His bundle recordings were repeated during follow-up in 48 survivors after a mean period of 7.2 +/- 0.7 months. Infranodal conduction delay in the acute stage of infarction was correlated with a higher incidence of heart failure during AMI (78% of patients in group A vs 22% in group B, p less than 0.001), and with higher rate of cardiac mortality during follow-up (50% in group A vs 13% in group B, p less than 0.01). Survivors of group A showed a higher functional NYHA class, a higher incidence of CHF, and a higher prevalence of complex ventricular arrhythmias at Holter monitoring. No statistically significant difference in late sudden death was evident between the two groups of patients, and the global incidence of late AV block was 2%. At repeat His bundle recording no significant change (greater than 5 ms) in HV interval could be demonstrated in comparison to the acute phase recording, neither in patients with prolonged nor in patients with normal HV time. We conclude that HV prolongation in patients with isolated, post-infarctional IVCD is correlated with a worse prognosis, both during acute infarction and during the follow-up period, which presumably reflects wider anatomic damage in comparison to patients with normal HV time. The low incidence of late AV block and the electrophysiological demonstration of the stability of infranodal conduction several months after AMI indicate that these patients do not require permanent prophylactic pacing after acute myocardial infarction.

Pullout His bundle/electrophysiologic studies using leads previously inserted via the subclavian vein

Conventional electrophysiologic studies involve the insertion of several catheter electrodes, positioned to pace and record from the high right atrium, His bundle region, and the right ventricular apex. The present study was undertaken to determine whether similar information could be obtained during removal of temporary pacing leads previously inserted via the subclavian vein, without the need for further invasive studies. Attempts to record a His bundle potential were successful in 157 of 200 patients (79%). A His bundle potential could be recorded during low right atrial pacing on 24 of 58 attempts. The Wenckebach cycle length was compared during high and low right atrial pacing in 34 patients, and did not differ significantly. Ventricular stimulation from the right ventricular apex and right ventricular inflow tract could be performed for assessment of ventricular vulnerability. Similarly, high right atrial pacing for sinus node testing was readily accomplished. In conclusion, detailed electrophysiologic studies can be performed during termination of temporary pacing, in sufficient detail to provide results equivalent to those of a more formal study.

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

In a previous study patients with bundle branch block complications acute anteroseptal infarction 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.

Bundle branch block after myocardial infarction--a long term follow-up

Fifty-two patients with myocardial infraction complicated by bundle branch block (27 RBBB and 25 LBBB) survived the hospital period (1967--1972), and were followed up to December 1976. Actuarial survival curves revealed a worse mortality up to five years (P less than 0.05) for LBBB (68%) than for RBBB (33%). All deaths occurred in the first four years. In RBBB, additional hemiblock (seven patients) did not increase the risk of heart block nor worsen the prognosis--one death in seven patients (14%) compared to eight in 20 patients with isolated RBBB (40%). The previous literature on long term survival of BBB was reviewed. Recommended treatment for BBB, a marker of severe myocardial damage, includes antiarrhythmic prophylaxis for anteroseptal infarction with RBBB, aneurysmectomy in selected subsets of patients, and possibly prevention of RBBB or its complications by treatment for reduction of infarct size during the very early phase after onset of infarction.

The prognostic value of the HV interval in patients with acute myocardial infarction and bundle branch block

HV intervals were measured in 42 of 119 patients in the acute phase of myocardial infarction associated with bundle branch block (BBB). The mean HV intervals of patients with right, left and incomplete bilateral BBB were similar. The hospital and subsequent mortality of patients with prolonged HV intervals did not differ significantly from that of patients with normal HV intervals. The HV interval appeared to remain stable over the following months in most patients in whom it was remeasured. We conclude that the HV interval cannot be used to select patients who might benefit from prophylactic long term pacing.

Histopathology of conducting system in left anterior hemiblock

In 8 cases of left anterior hemiblock, combined with right bundle-branch block in 7, serial sections of the conducting system of the heart were examined histologically. In all cases there were pathological changes in the left bundle-branch but the anterior part of it was predominantly affected in only 2 cases. Acute changes were found in 6 cases of early myocardial infarction, and fibrosis in 2 cases of chronic heart disease. Reversible lesions may have a pathogenetic role in acute hemiblocks. The right bundle-branch was disrupted by fibrosis in 6 of the 7 cases with right bundle-branch block, and minor changes in the AV node were observed in 1. The widespread damage to the left bundle-branch in the majority of the present cases does not seem to be consistent with the limited clinicopathological correlation implied by the terms anterior fascicular block or hemiblock. Other cardiac lesions within the left bundle-branch and outside it may contribute to this electrocardiographic pattern.