Effect of thrombolysis on heart rate variability and life-threatening ventricular arrhythmias in survivors of acute myocardial infarction

Objectives. The aim of the present study was to determine the influence of early thrombolysis on ventricular tachyarrhythmias (clinical and inducible) and heart rate variability in survivors of myocardial infarction at high risk for life-threatening ventricular arrhythmias.Background, A greater electrical heart stability may be important in improving survival in patients treated with thrombolysis. Few data are available about the influence of fibrinolysis on postinfarction arrhythmic events and other prognostic variables, such as inducible ventricular tachycardia and heart rate variability.Methods. The study group comprised 51 consecutive patients who underwent electrophysiologic study within 30 days of infarction, owing to the presence of two or more of the following criteria: left ventricular ejection fraction <40%, late potentials and repetitive ventricular ectopic beats. Thirty patients underwent thrombolysis within 6 h of the onset of symptoms (Group A), and 21 received conventional treatment (Group B). Inducibility of sustained monomorphic ventricular tachycardia was tested in both groups, and the standard deviation of all normal RR intervals during 24-h Holter monitoring was calculated. All patients were prospectively evaluated for occurrence of arrhythmic events.Results. The two groups were similar with regard to left ventricular ejection fraction (mean ± 1 SD 38 ± 6% [Group A] vs. 36 ± 8% [Group B]). Ventricular tachycardia was induced in 6 (20%) of 30 Group A patients versus 14 (67%) of 21 Group B patients (p = 0.002). The standard deviation of normal RR intervals was higher in Group A than in Group B (113 ± 36 vs. 90 ± 39 ms, p = 0.05). In patients with anterior infarction, the standard deviation of normal RR intervals was higher in 19 patients with thrombolysis than in 16 patients with conventional treatment (118 ± 41 vs. 74 ± 24 ms, p = 0.0002). During a mean follow-up period of 23 ± 11 months, 4 (13%) of 30 Group A patients had an arrhythmic event versus 9 (43%) of 21 Group B patients (p = 0.04).Conclusions. After myocardial infarction, in high risk patients, thrombolysis significantly reduced the occurrence of arrhythmic events independently of left ventricular function. This effect may be related to both an improvement in electrical heart stability, as elucidated by electrophysiologic study, and a favorable action on the cardiac sympathovagal balance.