Prevalence and prognostic significance of ventricular arrhythmias after acute myocardial infarction in the fibrinolytic era. GISSI-2 results

Abstract

Background: Several studies performed before the advent of thrombolysis have shown that the presence of ventricular arrhythmias is an independent risk factor for subsequent mortality in patients recovering from acute myocardial infarction. Since fibrinolysis affects the natural history of infarction and may alter the clinical relevance of different risk factors, the aim of the present study was to establish the prevalence and prognostic value of ventricular arrhythmias in post-myocardial infarction patients treated with fibrinolytic agents during the acute phase.

Methods and results: Twenty-four-hour Holter recordings obtained before discharge from the hospital in 8,676 post-myocardial infarction patients of the GISSI-2 study were analyzed for the presence of ventricular arrhythmias. Patients were followed for 6 months from the acute event; total and sudden cardiovascular mortality rates were computed, and relative risks in univariate and multivariate analyses were calculated. Ventricular arrhythmias were present in 64.1% of the patients, more than 10 premature ventricular beats per hour were recorded in 19.7% of the patients, and nonsustained ventricular tachycardia was present in 6.8% of the patients. Ventricular arrhythmias were more frequent when signs or symptoms of left ventricular damage were present. During follow-up, there was a total of 256 deaths 2.0% in patients without ventricular arrhythmias, 2.7% in patients with one to 10 premature ventricular beats per hour, 5.5% in those with more than 10 premature ventricular beats per hour, and 4.8% in those with complex premature ventricular beats. Even after adjusting for several risk factors, the presence of frequent (more than 10 premature ventricular beats per hour) ventricular arrhythmias remained a significant predictor of total (RRCox, 1.62; 95% confidence interval, 1.16-2.26) and sudden mortality (RRCox, 2.24; 95% confidence interval, 1.22-4.08). On the other hand, the presence of nonsustained ventricular tachycardia was not associated with a worsening of the prognosis in the adjusted analysis (RRCox, 1.20; 95% confidence interval, 0.80-1.79).

Conclusions: This study shows that approximately 36% of patients recovering from acute myocardial infarction presented with less than one premature ventricular beat per hour in Holter recordings obtained before discharge from the hospital, whereas almost 20% of patients showed frequent (more than 10 premature ventricular beats per hour) ventricular arrhythmias. Due to the large size of the population of this study, these figures may be used as a reliable estimate of the prevalence of arrhythmias in postinfarction patients treated with fibrinolytic agents during the acute phase. Frequent premature ventricular beats are confirmed as independent risk factors of total and sudden death in the first 6 months following the acute event; the significance of nonsustained ventricular tachycardia in this population appears more controversial.