Aortic reaction to prolonged nonpulsatile left heart bypass

Abstract

We investigated the reaction of the vascular system to prolonged nonpulsatile left heart bypass (LHB) using adult goats that underwent chronic nonpulsatile LHB. On morphological examination of the aorta, we found a decrease in wall thickness, a decrease in constituent volume ratio of smooth muscle, and an increase in the ratio of elastin. The atrophic change was further confirmed by an increase in smooth muscle cell density and an increase in smooth muscle cells, which exhibited atrophy-specific changes on electron microscopic observation. The changes in mechanical properties accompanying these morphological changes were evaluated according to stiffness parameter β and pulse wave velocity. No significant changes in those parameters were caused by prolonged nonpulsatile LHB. The change in vascular contractility was evaluated by the response of systemic vascular resistance to norepinephrine and nitroglycerin administration. Vascular contractility was markedly decreased by prolonged nonpulsatile LHB. These results indicated that the significant morphological changes, including aortic structure and smooth muscle atrophy, were caused by prolonged nonpulsatile LHB. However, these changes did not accompany the changes in mechanical properties. In contrast, this distinctive LHB modality caused a decrease in vascular contractility.