Comparison of verapamil versus felodipine on heart rate variability in hypertensive patients

Objective We evaluated the effect of two calcium channel blockers, verapami l and felodipine, on heart rate variability in hypertensive patients. Design Time and frequency domain measures of heart rate variability were ob tained from 24 h Holter recording in 25 previously untreated hypertensive p atients without left ventricular hypertrophy, before and after 3 months of verapamil slow-release treatment (240 mg once daily) or felodipine extended -release treatment (10 mg once daily). Results Blood pressure values decreased with both drugs. Measures of heart rate variability, comparable at baseline in the two groups, were unchanged after felodipine. After verapamil, the average RR interval, the square root of the mean of the squared differences between all adjacent normal RR inte rvals (r-MSSD) and the percentage of differences between all adjacent norma l RR intervals >50 ms (pNN50), measures of vagal modulation of heart rate, increased (from 735 +/- 67 to 827 +/- 84 ms, P < 0.001; from 30 +/- 10 to 4 4 +/- 15 ms, P < 0.001; and from 3 +/- 2 to 7 +/- 6%, P < 0.01, respectivel y) and were higher than after felodipine. The coefficient of variation, a m easure that compensates for heart rate effects, increased only after verapa mil (from 5.8 +/- 1.3% to 6.6 +/- 1.0%; P < 0.05). High frequency power and its coefficient of component variance, both representing the vagal modulat ion of heart rate, increased after verapamil (from 5.33 +/- 0.29 to 5.80 +/ - 0.27 In units, P < 0.001 and from 1.9 +/- 0.3 to 2.2 +/- 0.25%; P < 0.05) . Finally, the low to high frequency power ratio, an indicator of sympathov agal balance, with a high value suggesting a sympathetic predominance, decr eased after verapamil (from 2.16 +/- 0.41 to 1.36 +/- 0.35; P < 0.001), con firming the improvement in vagal modulation of heart rate. Conclusion In hypertensive patients, despite a comparable anti-hypertensive effect, verapamil, but not felodipine, has favourable effect on cardiac au tonomic control. J Hypertens 1999, 17:707-713 (C) Lippincott Williams & Wil kins.