Microcirculation in Graft Failure

Abstract

The term microcirculation refers to arterioles, capillaries, and venules with a diameter between 5 and 250 μ(mu)m, with important autocrine and paracrine functions involved in the regulation of normal vascular tone. The methods used to assess microcirculation are noninvasive and invasive techniques demonstrating induced myocardial ischemia, myocardial perfusion defects, coronary flow response to hyperemia, and coronary flow reserve (CFR). Microcirculation dysfunction can accompany lesions of epicardial coronary arteries and of myocytes, or may occur in the absence of other vascular or myocardial lesions. During coronary graft surgery the vascular endothelium and vascular smooth muscle cells are damaged, microemboli appear, and acute thrombosis is favored. Over time, grafts subjected to increased pressure suffer persistent endothelial injury. It is considered that the persistence of microvascular dysfunction explains angina after percutaneous or surgical revascularization. The study of microcirculation may provide important contributions to the understanding of the pathophysiological substrate of myocardial ischemia in patients with coronary artery graft.