Effect of thrombolysis on heart rate variability and life-threatening ventricular arrhythmias in survivors of acute myocardial infarction
ABSTRACT 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.
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ABSTRACT: Despite the growing evidence for the positive predictive value of depressed baroreflex sensitivity and/or reduced heart rate variability after myocardial infarction, the mechanisms involved in these autonomic alterations are not fully understood. Specifically, the possible influence of residual ischaemia has not been assessed. To address this problem we studied the spectral analysis of heart rate variability in 21 patients with a first myocardial infarction in whom the only clinical correlate was the presence of residual ischaemia, as documented by the positive response to both an exercise stress test and an echocardiographic stress test. Data from these patients were compared with those obtained in a group of postmyocardial infarction patients similar for several risk factors, age, site of myocardial infarction, but without residual ischaemia. Patients positive for residual ischaemia had lower power in the whole spectrum (1146 +/- 158 vs 1631 +/- 159 ms2, P = 0.032) as well as in the low and high frequency bands of heart rate variability. A nocturnal increase in high frequency was observed in those without residual ischaemia (from 167 +/- 35 to 242 +/- 51 ms2, +45%, P = 0.034), but not in those with residual ischaemia (from 111 +/- 19 to 141 +/- 29 ms2, +27%, ns). Thus, residual ischaemia reduces heart rate variability after myocardial infarction. The autonomic effects of residual ischaemia probably contribute to its negative prognostic value after myocardial infarction.European Heart Journal 02/1997; 18(1):78-83. · 10.48 Impact Factor