HEART-RATE-VARIABILITY AND MAJOR ARRHYTHMIC EVENTS IN PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY

This prospective study of 71 patients with idiopathic dilated cardiomy opathy (IDC) and preserved sinus rhythm was designed to evaluate the r elation between heart rate variability (HRV) and subsequent major arrh ythmic events. Standard time- and frequency-domain HRV parameters were obtained from analysis of 24-hour Holter ECG recordings. During a mea n follow-up of 15 +/- 5 months, major arrhythmic events including sust ained ventricular tachycardia, ventricular fibrillation, and sudden ca rdiac death occurred in 10 of the 71 study patients (14%). Neither tim e- nor frequency-domain indices of HRV differed significantly between patients with and patients without subsequent major arrhythmic events. However, there was a trend toward a lower standard deviation of the a verage normal RR interval for all 5-minute segments of the 24-hour rec ording (68 +/- 17 ms vs 80 +/- 31 ms; P = 0.06) in patients with major arrhythmic events. In addition, the percentage of adjacent normal RR intervals differing > 50 ms over the recording period tended to be low er in patients with major arrhythmic events (6% +/- 3% vs 9% +/- 6%; P = 0.08). Our results indicate a tendency toward attenuated parasympat hetic activity in IDC patients with subsequent major arrhythmic events compared to arrhythmia-free patients. Larger studies with longer foll ow-up periods are necessary to clarify the role of HRV measurements fo r arrhythmia risk prediction in patients with IDC.