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[Effect of nifedipine and enalapril on cardiac autonomic activity in elderly hypertensive patients].

To clarify the effect of the calcium antagonist Nifedipine and the ACE inhibitor Enalapril on cardiac autonomic activity, power spectral analysis of heart rate variability (PSA) was conducted in 39 elderly patients with essential hypertension (mean age: 63: +/- 11 years) before and after treatment. Twenty patients were treated with 10-20 mg of Nifedipine (N group) and 19 with 5 mg of Enalapril (E group) for 3 months. beta-blocker (Atenolol 12.5 mg) was added to Nifedipine in 12 patients of the N group for 1 month, and the modified effect of Atenolol on cardiac autonomic activity was also evaluated. Blood pressures were significantly reduced in both N and E groups after the treatment. The low frequency component (LF) in PSA, which was considered to be a quantitative marker of cardiac sympathetic activity, increased significantly and the high frequency component (HF), which was a marker of cardiac parasympathetic activity, significantly decreased with increase of PNA levels in N group after the treatment. However, the LF decreased significantly after addition of Atenolol. On the other hand, there was little significant change in LF and PNA in E group. These results suggest that Nifedipine increased cardiac sympathetic activity and that Enalapril had little influence on the cardiac sympathetic tone, while both antihypertensive agents significantly reduced blood pressure itself.