The effect of infarct size on atrioventricular and intraventricular conduction disturbances in acute myocardial infarction

Abstract

The effect of infarct size estimated from serial CK-MB isoenzyme determinations on the incidence of atrioventricular and intraventricular conduction disturbances was examined in 250 patients suffering their first myocardial infarction. The size of the infarct was significantly greater ( P < 0.001) in 72 patients with conduction disturbances than in 178 without conduction defects (54 ± 29 vs. 35 ± 22 CK-MB gEq). The largest size was observed in 10 patients with bifascicular block (71 ± 38 CK-MB gEq). Within the group of patients with intraventricular conduction disturbances, the size of the infarct was significantly greater ( P < 0.01) when localized inferiorly rather than anteriorly (91 ± 10 vs. 58 ± 27 CK-MB gEq). The size in those patients with complete atrioventricular block and anterior infarction was larger than in those with an inferior lesion (76 ± 21 vs. 52 ± 33 CK-MB gEq). The size in those patients with inferior infarction and complete block was significantly greater ( P < 0.05) than in patients with similarly positioned infarction without conduction disturbances (52 ± 33 vs. 35 ± 22 CK-MB gEq). There was no significant difference in the size of infarct when inferior infarction was complicated by first- and second-degree block in comparison to those without conduction defects (38 ± 23 vs. 35 ± 22 CK-MB gEq). A correlation was observed between the size of infarction and the incidence of conduction disturbances ( P < 0.001); the greater the size the higher the incidence of conduction disturbances.