Conduction disturbances due to anteroseptal myocardial infarction and their treatment by endocardial pacing

Conduction disturbances complicated anteroseptal myocardial infarction in 70 patients admitted to a coronary care unit. The hospital mortality rate of these patients was 73 per cent. Right bundle branch block (RBBB) was the commonest abnormality, and this progressed to complete atrioventricular (A-V) block in one third of cases. Nearly all cases of A-V block were complicated by episodic ventricular asystole. Surprisingly, A-V block was no more common in patients showing partial left bundle branch block (LBBB) in addition to RBBB (partial bilateral BBB) than in those who had pure RBBB. In patients who died, proximal obstruction of the anterior descending coronary artery was a constant finding, although extensive involvement of other vessels was also frequent. Neither prophylactic demand pacing for RBBB nor pacing for established A-V block appeared to reduce the high hospital mortality rate, although pacing was considered to have been life saving in two patients. Pacing prolonged life for a few days in a large proportion of patients who died, however, and in several of these patients the conduction disturbances were reversible and death finally occurred from another cause. Pacing would be a useful temporary procedure if some more definitive treatment for this condition was available.