To discern the relative prognostic role of complete atrioventricular block (CAVB) in patients with acute myocardial infarction (AMI), 908 consecutive patients with AMI were studied over a 7-year period. Of the 559 patients with anterior wall AMI, 13 (2.3%) demonstrated CAVB, of whom 10 (76.9%) died in the hospital (vs 10.4% in those without CAVB) (p less than 0.001). In 349 patients with inferior wall AMI, 30 (8.6%) developed CAVB, of whom 6 (20%) died (vs 6.3% in those without CAVB) (p less than 0.01). In anterior wall AMI, all 5 patients with narrow QRS complexes (vs 8/11 with wide QRS complexes) (p = NS) died; in inferior wall AMI, 4/25 with narrow QRS complexes (vs 2/5 with wide QRS complexes) (p = NS) died. The mortality rate of patients with an escape frequency of less than or equal to 50/min did not differ significantly from that of patients with greater than 50/min regardless of the site of infarction or whether a pacemaker was used. In anterior wall AMI, the mortality rate of paced patients was 70% (7/10) compared to 100% (3/3) of non-paced patients (p = NS). In inferior wall AMI, the mortality rate of paced (5/25) and non-paced (1/5) patients was both 20%. Thus, none of the clinical parameters such as escape rhythm, the width of escape QRS complexes and pacemaker therapy discriminated the survivors from the deaths. In anterior wall AMI, episodes of cardiac standstill or bradycardia were of short duration, and pacemaker therapy was only one of the therapies applied.(ABSTRACT TRUNCATED AT 250 WORDS)