[Complete bundle-branch block and myocardial infarct. Natural history. Comparative study].

Myocardial infarction (MI), (and especially anteriorly situated necrosis) was complicated by complete branch block (CBB) in 9.7% of cases (45 patients out of 462). A comparison of the short- and long-term outcome in two groups of patients (group A: 45 cases of MI complicated by CBB; group B: 45 cases of MI with no atrio-ventricular or intra-ventricular conduction defects) showed that there was a much bigger immediate mortality in group A, which was not changed by temporary cardiac pacemaking, and depended on the extent of myocardial destruction. A study of the long-term outcome showed that there were more deaths in group A (recurrence of MI, intractable cardiac failure). However, the incidence of sudden death was equal in the two groups (group A 15%, group B 13%), and there was no obvious explanation in the absence of electrocardiographic tracings. Therefore this study lends no support to the argument which favours prophylactic implantation of a cardiac pacemaker during the course of MI complicated by CBB.