Effect of verapamil on heart rate variability in subjects with normal hearts.

Heart rate variability on 24-hour electrocardiographic recording was assessed in 23 patients without structural heart disease before and after 2 months of oral treatment with verapamil prescribed for paroxysmal atrioventricular nodal reentrant tachycardia. Verapamil had no significant effect on overall heart rate variability in the frequency domain, but it increased ultra low frequency power and decreased the low-frequency/high-frequency ratio, deemed to be a marker of sympathetic activity.