EFFECT OF MORICIZINE ON HEART-RATE-VARIABILITY IN NORMAL SUBJECTS

We investigated the effects of moricizine HCl, a type Ic anti-arrhythm ic agent, on heart rate variability. Decreased heart rate variability is a risk factor for mortality in post-MI and other patient population s, and some antiarrhythmic drugs decrease heart rate variability. Norm al volunteers (10 M, 11 F, age 19-39 years) received blinded placebo a nd moricizine HCl at 200 mg twice daily for 5 days. On day 4, a 24-h E CG was obtained, and time and frequency domain measures of heart rate variability based on normal-to-normal intervals were computed. Moriciz ine decreased both time and frequency domain measures of heart rate va riability. Significant reductions were seen for SDNNIDX (the average S .D. for N-Ns for each 5-min interval in ms) and pNN50 (the proportion of successive N-N differences > 50 ms in percent) in the time domain, and very low (0.0033-0.04 Hz), low (0.04-0.15 Hz) and high (0.15-0.4 H z) frequency power. Similar patterns of change in heart rate variabili ty were seen when data for daytime and nighttime periods were analyzed separately. rMSSD (the root mean square successive difference of N-N intervals in ms), pNN50 and high frequency power are primarily indices of parasympathetic tone. SDNNIDX, and very low and low frequency powe r reflect both sympathetic and parasympathetic tone and longer term va riability. Thus, and longer term components of heart rate variability. This decrease produced by with other type 1 antiarrhythmics.