Intraventricular blocks in acute myocardial infarction.

The electrocardiograms and clinical records of 171 patients with a first recognized myocardial infarction (AMI) were reviewed in order to study the incidence and clinical significance of intraventricular blocks (IVB), especially hemiblocks, when other conditions which could have influenced the prognosis were excluded. Patients with left anterior hemiblock had higher SGOT levels (p less than 0.01), higher incidence of arrhythmias (p less than 0.01) and congestive heart failure (p less than 0.01) compared to the control group without IVB. Isolated left posterior hemiblock was infrequent and did not appear to influence the course of AMI. Bundle branch and bifasicular blocks were associated with the highest incidence of complications and mortality (47 percent), but these patients were older (p less than 0.01) and also had higher SGOT levels than the control group (p less than 0.05). To some extent, mortality and incidence of complications appeared to be related to the degree of myocardial damage, which in turn produced the IVB rather than to the conduction abnormality itself.