Power Spectral Analysis of Heart Rate in Elderly Hypertensive Subjects With or Without Silent Coronary Disease

Much evidence indicates an involvement of the sympathetic nervous system in the genesis of silent myocardial ischemia. The authors assessed autonomic system activity by power spectrum analysis of heart rate variability in 21 elderly hypertensive men with and without angiographically confirmed coronary artery disease and compared the results with those from an age-matched control group. In the analysis an autoregressive algorithm was used to determine the power spectrum from an electrocardiographic recording of 512 consecutive RR intervals. The autonomic nervous system induces two distinct sinusoids: a low-frequency signal attributable to sympathetic activity and a high-frequency vagal response. In the hypertensive patients with coronary disease the authors also evaluated sympathetic activation after double-blind, placebo-controlled administration of metoprolol (100 mg/day), followed by amlodipine (10 mg/day), quinapril (20 mg/day), and amlodipine (5 mg/day) plus quinapril (10 mg/day). (continued on next page) Spectrum analysis showed significantly increased sympathetic activity in the hypertensive patients with coronary disease (low frequency: 58.4 ±2.0, P < 0.001) as compared with controls (36.21 ± 1.0, P < 0.001) and hypertensive subjects without coronary disease (low frequency: 25.2 ±0.6 , P < 0.001) but significantly reduced parasympathetic activity (39.4 ±2.0, P < 0.001) with respect to hypertensive patients without heart disease (42.5 ±2.0, P < 0.001) and controls (60.3 ±2.0). Treatment with metoprolol, quinapril, and amlodipine plus quinapril significantly reduced sympathetic tone (P < 0.05).