Significance of Early and Late Atrioventricular Block in Patients with a Q Wave Acute Inferior Myocardial Infarction

Abstract

One hundred and seventeen consecutive patients (mean age 55 years) with Q wave acute inferior myocardial infarction (MI) were studied. Of these, 62 developed atrioventricular (AV) conduction disorders (group I) and 55 did not (group II). The AV block occurred early (within 24 h) in 38 (Ia) and later in 24 patients (Ib). We report the in-hospital morbidity and mortality of these acute MI patients. There were no significant differences between group Ia and Ib patients with respect to coronary artery disease risk factors. Right ventricular MI was diagnosed in 14 (36%) and 7 (29%) group Ia and Ib patients, respectively (p = NS), and in 5 (9%) of group II patients. Mean peak serum creatine kinase was highest in group Ia patients (2,403 IU/1) compared to 1,860 IU/1 in group Ib and 1,369 IU/1 in group II. There was cardiogenic shock in 11 patients with 10 deaths in group Ia, while in group II, 2 patients had cardiogenic shock and 3 died (p < 0.01). Only mortality was significantly higher in group Ia compared to group Ib (p < 0.05). Cardiogenic shock was twice the rate in group Ib (n = 4) compared to group II (n = 2; p < 0.05), but there was no difference in mortality. A complete AV block was present in 32 patients (84 %), with 25 (66 %) requiring a pacemaker in group Ia, compared to 9 (37%), with 8 (33%) requiring a pacemaker, in group Ib (p < 0.01). We conclude that prognosis is poor with the appearance of an AV block ≤ 24 h after Q wave acute inferior MI, although mortality in patients with late AV block ( > 24 h) remains similar to those without this complication. Cardiogenic shock may be higher in patients with AV block ≤ 24 h.