A prospective and preliminary observation of cardiovascular responses to the head-up tilting test in patients with over 1-year follow-up after coronary artery bypass grafting

Abstract

Hori et al. have suggested previously that blood pressure during a head-up tilt (HUT) in a patient after CABG at discharge was likely to decrease, even they took exercise therapy. Medication status after CABG and reduced stroke volume, one of index for blood volume, would be related with it. On the other hand, some natural adaptations to orthostatic stress in the patients may be expected over long-term recovery. However, there was no study to assess blood pressure during HUT after CABG while monitoring medication status and stroke volume over a long period. Changes in cardiovascular responses to HUT in 6 patients were preliminarily tested during supine and 15-min 60°HUT before (P0) and after coronary artery bypass grafting (CABG) (P1) and over 1-year after surgery (P2). Mean arterial pressure (MAP) decreased during HUT at P0 and P1 and the decrease at P1 was greater than P0, while it remained unchanged at P2. Heart rate (HR) increased during HUT at P0 and P1 and the increase at P1 tended to be greater than P0, while that at P2 were comparable to P0. Stroke volume (SV) was 30% lower during baseline at P1 and P2 than P0. Cardiac output reduced by HUT at P0, but was not affected at P1 and P2, while the baseline at P2 was lower than P0. Ejection fraction remained unchanged at 3 periods. In conclusion, baseline SV at P2 remained lower than P0, but MAP was maintained during HUT. The present results suggest that although the poor control of blood pressure just after is improved over 1 year after CABG, hypovolemia might not be corrected. Assessments of an exercise regimen over long term after CABG would be expected in the future.