Nifedipine and captopril exert divergent effects on heart rate variability in patients with acute episodes of hypertension.

Acute changes of heart rate variability (HRV) depict alterations in autonomic influences on cardiovascular system and often precede ventricular arrhythmias. The aim of the study was to assess effects of sublingual 10 mg nifedipine (n = 15) or 25 mg captopril (n = 13) on HRV in consecutive patients admitted to hospital due to severe hypertension. HRV was calculated on-line from 300 cardiac cycles before and 60-90 min after drug administration. At baseline systolic blood pressure (SBP) was > 190 mm Hg and/or diastolic blood pressure (DBP) > 110 mm Hg. Both agents caused similar reduction of blood pressure (BP). Nifedipine reduced variance (-63 +/- 6%; P < 0.0001) and high-frequency (HF) component (-72 +/- 8%; P < 0.0001), and increased both LF/HF ratio (+870 +/- 336%; P < 0.02) and heart rate (+14 +/- 3%; P < 0.0001). Captopril exerted different effects: variance and HF component increased by +176 +/- 55%; (P < 0.007) and +126 +/- 44% (P < 0.015), respectively. LF/HF (low/high frequency) ratio decreased (-44 +/- 19%; P < 0.04) together with heart rate (-4 +/- 1%; < 0.009). It is concluded that captopril, in contrast to nifedipine, increases HRV and decreases LF/HF ratio and therefore is a better choice in hypertensive patients who might be prone to dangerous arrhythmias.