Effect of partial arrhythmia suppression with amiodarone on heart rate variability of patients with congestive heart failure

Background Some antiarrythmic agents that may increase mortality rates have been shown to reduce heart rate variability in patients with heart failure. Amiodarone is a potent antiarrhythmic agent that may reduce mortality rates in heart failure, but little is known about its effects on heart rate variability. Methods and Results The purpose of this study was to evaluate the effect of partial arrhythmia suppression by amiodarone on indexes of heart rate variability in patients with heart failure. Ten clinically stable patients in New York Heart Association class II-III received amiodarone during a 4-week period (600 mg every day for 14 days and 300 mg every day for 16 days), and 24-hour Holter recordings were performed before and after treatment. Heart rate variability indexes were calculated by a semiautomatic method that applies a 20% filter to the temporal series, excluding ectopy and compensatory pauses. After amiodarone administration, there was a significant reduction in pNN50 from 8% +/- 7% to 3% +/- 2% (p < 0.05) and there was a trend toward reduction in rMSSD (p = 0.06). Other time domain indexes did not change significantly. Spec tral analysis demonstrated a significant reduction of low-frequency components (421 +/- 122 to 151 +/- 25 msec(2); p < 0.05) and total power (1503 +/- 314 to 609 +/- 144 msec(2), P < 0.05). Multivariate analysis showed that the observed reduction in pNN50 was strongly associated with the number and the reduction of ventricular premature contractions before and after amiodarone administration (r(2) = 0.94; p < 0.01). Conclusions These findings indicate that despite the use of software corrections for arrhythmia, short-term time domain indexes of heart rate variability may be effected by partial suppression of ectopy.