COMPARISON OF 3 RECUMBENT POSITIONS ON VAGAL AND SYMPATHETIC MODULATION USING SPECTRAL HEART-RATE-VARIABILITY IN PATIENTS WITH CORONARY-ARTERY DISEASE

Patients with coronary artery disease (CAD) have depressed vagal modul ation. Because the mortality risk from acute myocardial infarction is lower in patients with higher vagal modulation, methods that can incre ase vagal modulation are desirable for patients with CAD. The right la teral decubitus position has been found, in young healthy subjects, to lead to the highest vagal modulation among 3 recumbent positions usin g spectral heart rate variability (HRV) analysis, This study investiga ted which recumbent position can give rise to the highest vagal modula tion in patients with severe CAD. Twenty-seven patients scheduled for coronary artery bypass graft surgery and 17 patients with angiographic ally normal coronary arteries were studied. Spectral HRV analysis was performed in random order on these patients in 3 recumbent positions: namely, the supine, left lateral decubitus, and right lateral decubitu s positions. Normalized high-frequency power was the highest, whereas normalized low-frequency power and low/high-frequency power ratio in t he right lateral decubitus position were the lowest, among the 3 recum bent positions in both groups of patients, The lower the normalized hi gh-frequency power in the supine or left lateral decubitus position, t he higher the increase in the normalized high-frequency power when the position was changed from supine or left lateral decubitus to right l ateral decubitus in patients with severe CAD. Right lateral decubitus position can lead to the highest vagal modulation and the lowest sympa thetic modulation among the 3 recumbent positions in patients with sev ere CAD. Therefore, the right lateral decubitus position can be used a s an effective physiologic vagal enhancer in patients with severe CAD. (C) 1998 by Excerpta Medica, Inc.