Ventricular arrhythmias in the late hospital phase of acute myocardial infarction. Relation to left ventricular function detected by gated cardiac blood pool scanning

Abnormalities of left ventricular function and extent of myocardial infarction were studied in relation to prevalence of late ventricular premature contractions (VPCs) in 36 patients in the convalescent stage of acute myocardial infarction (MI). Left ventricular ejection fraction (EF) and percent akinesis (%A) were calculated from gated cardiac blood pool scans; myocardial infarct size was estimated from peak CPK values; and VPCs were detected by 24 hour ambulatory ECGs 2-4 weeks following hospitalization for acute MI. Twenty two patients had either zero (class O) or <30/hour unifocal VPCs (class I). Fourteen patients had > 30/hour unifocal (clas II), multifocal (class III) or coupled VPCs (class IV), including ventricular tachycardia. Thirteen of 14 class II-IV patients had EF <40% compared with only 8 of 22 class O-I patients. Class II-IV patients had significantly lower mean EF (30.5 ± 2.3 SE to 49.6 ± 4.0) P<0.01, higher mean %A (28.1 ± 2.2 to 16.9 ± 3.7) P<0.05, and higher mean peak CPK (1350 ± 187 to 721 ± 155) P<0.05 than class O-I patients. These data suggest that VPCs may not be an independent risk factor for sudden cardiac death in the convalescent phase of MI.