Neurohumoral and Pharmacologic Regulation of Collateral Perfusion

Abstract

In most species including humans, gradual coronary occlusion induces the development of coronary collaterals (1, 2). In some species these develop from preexisting vessels, and in others they develop anew (3). An aspect of coronary collateral development is the formation of a mature medial layer (4). This newly developed vascular smooth muscle provides a substrate for collateral vasomotion, and the regulation of collateral blood flow by neurohumoral influences. Furthermore, collateral perfusion must traverse not only collateral vessels but also vessels proximal to the collaterals per se, and also arterioles downstream from the collaterals. This series of resistances results in a unique situation in which regulation of collateral perfusion is subject to control mechanisms not present in normally perfused myocardium. In this chapter, several aspects of regulation of perfusion to collateral dependent myocardium will be considered, including unique vasomotor properties of mature collaterals, regulation of collateral perfusion by vessels proximal to the collaterals, and finally new findings regarding alterations of the vasomotor characteristics of recipient arterioles distal to collaterals.