Effect of prolonged nonpulsatile left heart bypass on vascular control status

Abstract

We investigated the vascular control status, including vasoactive hormones, systemic vascular resistance (SVR), and baroreceptor sensitivity, in prolonged nonpulsatile left heart bypass (NLHB). Nine goats underwent pulsatile left heart bypass (PLHB) with a ventricular assist device (VAD). Two weeks postoperatively, the VAD was replaced with a centrifugal pump and NLHB was subsequently conducted for 4 weeks. Thirteen healthy goats were also evaluated to obtain normal control data. The aortic pulse pressure on average was 37 mmHg for controls; 36mmHg at the end of PLHB; and 11, 9, 12, and 12mmHg at the end of the first, second, third, and fourth NLHB weeks, respectively. Plasma norepinephrine (NE), vaso-pressin (VP), renin activity (RA), and endothelin-I (ET) levels were measured for controls and at each point during PLHB and NLHB. The baseline SVR and the minimum SVR values after nitroglycerin injection were determined at each point during PLHB and NLHB. Baroreceptor sensitivity was calculated as the regression slope between R-R intervals and mean aortic pressure for controls and at each point during PLHB and NLHB. The plasma levels of NE, VP, RA, and EN did not change significantly during the entire course of the experiments. The baseline and minimum SVR values after nitroglycerin injection remained unchanged during PLHB and NLHB. Furthermore, the baroreceptor sensitivity did not change significantly during the entire course of the experiments. These results indicate that prolonged NLHB does not affect vascular control status, including the major vasoactive hormone levels, SVR, and baroreceptor sensitivity.