HEART RATE VARIABILITY POWER SPECTRA IN NORMAL SUBJECTS AND IN PATIENTS WITH CARDIAC DYSFUNCTION.

The power spectrum of heart rate variability (HRVPS) in humans has two major peaks; a 0. 1-Hz peak due to baroreflex control and a respiratory peak (0. 25-0. 35 Hz). Results are presented of investigations of normal subjects during the resting state, regulated breathing, standing, and during and following steady-state exercise. HRVPS results are also given for patients with autonomic neuropathy, following orthotopic cardiac transplantation, and during the acute stage of myocardiac infarction. In normal subjects, the 0. 1-Hz peak power increased significantly from supine to standing position and during post-exercise states (p less than 0. 05) while the 0. 1-Hz peak power was reduced during exercise (p less than 0. 05). Donor allografts from transplant patients showed a broad-based pattern with no consistent peaks. In patients with postural hypotension the 0. 1-Hz peak was nonexistent. In patients with myocardial infarction, the HRVPS appeared to be influenced by size rather than site of infarct.