Findings of prognostic value in patients with incomplete bilateral bundle branch block complicating acute myocardial infarction

The clinical course, serial electrocardiograms and His bundle electrograms were reviewed in 15 cases of incomplete bilateral bundle branch block complicating acute myocardial infarction. Fourteen patients had evidence of acute anterior wall myocardial infarction, one had additional evidence of acute inferior wall myocardial infarction and one had acute inferior wall myocardial infarction alone. Incomplete bilateral bundle branch block was manifested as right bundle branch block with left anterior hemiblock in 10 patients and as right bundle branch block with left posterior hemiblock in 4. One patient had right bundle branch block with periods of left anterior and left posterior hemiblock. Nine patients died between 9 hours and 6 weeks after admission; the six surviving patients have been followed up for 3 weeks to 6 months. In all patients a His bundle electrogram was obtained at the time of pacemaker insertion. Of the patients with an abnormal H—Q interval (55 msec or greater), eight died and three survived. Of those with a normal H—Q interval only one died and three survived. Examination of serial electrocardiograms showed that the right bundle branch block disappeared in four patients, of whom one died and three survived. Of the remaining patients with persistent right bundle branch block, eight died and three survived. All five patients with left posterior hemiblock had an abnormal H—Q interval, and four of these patients died. We conclude that in this group of patients, the prognosis is poor for those with an abnormal H—Q interval and persistent right bundle branch block and better for those with a normal H—Q interval and transient right bundle branch block.