Prognostic value of heart rate variability for sudden death and major arrhythmic events in patients with idiopathic dilated cardiomyopathy

OBJECTIVE This study was designed to evaluate the prognostic value of heart rate variability for sudden death, resuscitated ventricular fibrillation or sustained ventricular tachycardi in patients with idiopathic dilated cardiomyopathy. BACKGROUND Previous studies have shown that heart rate variability could predict arrhythmic events and sudden death in postinfarction patients, but the prognostic value of heart rate variability for arrhythmic events or sudden death in patients with idiopathic dilated cardiomyopathy has not been established. METHODS Time and frequency domain analysis of heart rate variability on 24-h electrocardiographic (ECG) recording was assessed in 116 patients with idiopathic dilated cardiomyopathy (91 men, aged 51 ± 12 years, left ventricular ejection fraction 34 ± 12%). RESULTS Mean follow-up (± SD) was 53 ± 39 months. Sixteen patients reached one of the defined study end-points (sudden death, resuscitated ventricular fibrillation or sustained ventricular tachycardia) during follow-up. Using multivariate analysis, only reduced standard deviation of all normal-to-normal intervals (SDNN) (p = 0.02) and ventricular tachycardi during 24-h ECG recording (p = 0.02) predicted sudden death and/or arrhythmic events. For SDNN, cutoff level of 100 ms seemed the best for the risk stratification. CONCLUSIONS Decrease in heart rate variability is an independent predictor of arrhythmic events and sudden death in idiopathic dilated cardiomyopathy, whether the mechanism of sudden death is ventricular tachyarrhythmi or not.