Risk stratification for malignant arrhythmic events in patients with an acute myocardial infarction: role of an open infarct-related artery and the signal-averaged ECG.

BACKGROUND

There is increasing evidence that an open infarct-related artery results in increased electrical stability of the heart and that this effect is at least in part responsible for the favorable outcome of these patients. In the thrombolytic era the optimal strategy for risk stratification remains controversial. This study examined the predictors of serious arrhythmic events during the first year after myocardial infarction.

METHODS

A total of 222 patients with acute myocardial infarction, 41.4% of whom were treated with thrombolysis, were studied. At hospital discharge, signal-averaged electrocardiography was performed on 196 subjects and Holter monitoring on 200. One hundred and ninety-seven patients underwent coronary angiography. Left ventricular ejection fraction was determined in 201 subjects.

RESULTS

An open infarct-related artery was documented in 106 patients. The incidence of late potentials was 34% (66 patients). Twenty-four patients (10.8%) had an arrhythmic event during follow-up (sudden death in seven, sustained ventricular tachyarrhythmias in 15, unexplained syncope in two). Signal-averaged electrocardiography had a sensitivity of 94% and a specificity of 72% for prediction of arrhythmic events. An occluded infarct-related artery was 78% sensitive and 58% specific, a left ventricular ejection fraction below 40% had a sensitivity of 71% and specificity of 80%, and Holter monitoring was only 38% sensitive and 92% specific. A combination of late potentials plus an occluded infarct-related artery was 68% sensitive and 84% specific. Positive predictive value was low for all variables examined, but could be improved by the combination of several risk factors. The highest positive predictive value was provided by the combination of an abnormal signal-averaged ECG and complex ventricular arrhythmias on ambulatory ECG. On multivariate analysis, in rank order, presence of late potentials, ejection fraction below 40%, high-grade ventricular ectopic activity and an occluded infarct-related artery were predictive of arrhythmic events.

CONCLUSION

Among patients surviving an acute myocardial infarction, the occurrence of malignant arrhythmic events can be reliably predicted by the combination of an abnormal signal-averaged ECG, left ventricular dysfunction, complex ventricular arrhythmias on Holter monitoring and an occluded infarct-related artery at the time of hospital discharge.