Effects of nifedipine and enalapril on cardiac autonomic nervous function during the tilt test in elderly patients with hypertension.

To clarify the effects of nifedipine and enalapril on cardiac autonomic nervous function during postural changes, power spectral analysis of heart rate variability and humoral factors was performed during tilt tests before and after 3 months of drug administration. The study group consisted of 29 elderly patients with hypertension (mean age, 69 yr), who were divided into two groups: 15 patients received nifedipine (group N) and 14 received enalapril (group E). In group N, systolic blood pressure was significantly decreased and the percent changes in low-frequency coefficient of component variance, normalized low-frequency: high-frequency ratio, and plasma norepinephrine concentration were significantly altered by nifedipine administration. Group E, in contrast, showed no significant decrease in SBP, and only the percent change in high-frequency coefficient of component variance increased significantly after enalapril administration. These results suggest that cardiac autonomic nervous function is markedly impaired during the tilt test after long-term treatment with nifedipine, whereas it is well-maintained after long-term treatment with enalapril.