Incidence and prognosis of secondary ventricular fibrillation in acute myocardial infarction. Evidence for a protective effect of thrombolytic therapy. GISSI Investigators.

The multicenter randomized study of the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico has provided the opportunity to analyze the impact of thrombolytic treatment on secondary ventricular fibrillation incidence in a large population of patients (11,712) with acute myocardial infarction. A reduction of about 20% in the frequency of secondary ventricular fibrillation was observed among patients allocated to thrombolytic treatment (streptokinase, 2.4% versus control, 2.9%; relative risk, 0.80; 95% confidence interval, 0.64-1.00). Streptokinase appeared to exert its protective effect specifically in patients treated within 3 hours of onset of symptoms (streptokinase, 2.6% versus control, 3.7%; relative risk, 0.71; 95% confidence interval, 0.53-0.95). This protection was essentially due to a reduced incidence of late ventricular fibrillation occurring after the first day of hospitalization. The 311 patients with secondary ventricular fibrillation represented an overall incidence of 2.7%. Such incidence was not related to infarct location or sex but was significantly more common in patients older than 65 years (3.3% versus 2.3% in younger patients). A significant excess of in-hospital deaths was found in patients with secondary ventricular fibrillation compared with those in the reference group (38% versus 24%; relative risk, 1.98; 95% confidence interval, 1.56-2.52). Conversely, secondary ventricular fibrillation was not a predictor of 1-year mortality for hospital survivors. Thrombolytic treatment with intravenous streptokinase affords protection against secondary ventricular fibrillation most probably by a limitation of infarct size. When the arrhythmia complicates the course of infarction, it is associated with an adverse short-term outcome, whereas the long-term prognosis is not influenced.