Myocardial infarct size: correlation with cardiac arrhythmias and sudden death.

The study was made in order to determine the relationship between myocardial infarct size and the incidence of cardiac arrhythmias during acute myocardial infarction (AMI). In 317 consecutively admitted patients infarct size was estimated from serial serum CK-MB measurements. The ECG was continuously monitored during 18 days in hospital, and all electrocardiographic recordings were analysed daily. All patients were followed up one year after discharge. The median infarct size was larger among the 220 patients with arrhythmias than among the 97 patients without (814 Ul-1 vs 419 Ul-1, P less than 0.0001). There was a significant relationship between the estimated infarct size and the following arrhythmias: ventricular ectopic beats, sinus tachycardia, and atrioventricular block, whereas supraventricular ectopic beats showed no such relation. Patients with heart failure, however, had a high incidence of ventricular arrhythmias regardless of the size of their infarcts. The follow-up study demonstrated that the ventricular arrhythmias positively correlated with infarct size were also associated with significantly increased one-year mortality among hospital survivors. Thus, the present study indicates that not only pump failure, but also cardiac arrhythmias are connected with the negative influence of infarct size on prognosis.