[Electrophysiologic study of the intraventricular conduction disorders complicating acute myocardial infarct. Evaluation in the acute phase and follow-up].

In order to investigate the natural history and to evaluate the long-term risk of progression of the intraventricular (IV) conduction disturbances (CD) that complicate acute myocardial infarction (AMI), we prospectively followed the electrophysiological evolution of the IVCD in 47 patients admitted to our CCU in the years 1978-81 (34 anterior wall AMI, 13 inferior wall AMI; LAFB in 7, RBBB in 12, RBBB + LAFB in 13, RBBB + LPFB in 7, and LBBB in 8 cases). Only patients who acquired the IVCD after AMI and who did not develop 2 or 3 or 3 degrees degree AV blocks during the acute phase were considered. A His bundle recording (HBR) was obtained in every patient at the time of IVCD appearance. The HV interval was greater than 55 msec in 13 and less than or equal to 55 msec in 34. The study was repeated in 37 survivors after 3-20 months, mean 12. No significant change in infra His bundle conduction time was demonstrated at repeat HBR; the HV interval remained to be prolonged in all 8 patients with previously prolonged HV interval, and normal in all 29 patients with previously normal infra His bundle conduction time. The incidence of infra His bundle conduction delays was correlated with the degree of cardiac functional impairment, either during the acute phase or at follow-up. Late cardiac mortality rate was significantly higher for patients with HV prolongation during AMI (6/13 = 46%), compared to patients with normal HV interval (5/34 = 14%), (p less than 0.01). Two patients died suddenly during the follow-up period, both had had HV prolongation during AMI; all other deaths were due to reinfarction or to congestive heart failure. Our data indicate that patients who develop an IVCD, without advanced AV block, during AMI, do not exhibit late progressive deterioration of their infra His bundle conduction, whether it was normal or prolonged during AMI. The risk of late AV block seems to be negligible for patients with normal HV interval, while it cannot be overlooked in patients with prolonged HV interval during the acute phase of myocardial infarction.