The pathophysiology of the collateral circulation (arteriogenesis)

Since the mid 1980s a new strategy is coming from bench to bedside termed a ngiogenesis. This process involves sprouting of capillaries and finally res ults in newly developed microvessels which belong to the capillary level. I mportantly these newly formed capillary tubes lack vascular smooth muscle c ells, they are not surrounded by mural cells and are fragile and prone to r upture. Therefore these networks remain susceptible to hypoxic regulation, fail to become remodelled and are unable to sustain proper circulation: the y cannot adapt to changes in physiological demands of blood supply. Since a therosclerosis affects large conductance arteries, capillary sprouting from compromised vessels cannot provide an adequate supply of blood how to the endangered tissue. However, the body provides a natural system of pre-exist ing collateral arteries, which may bypass sites of arterial occlusion. Thes e vessels can dramatically increase their lumen by growth SO as to provide enhanced perfusion to the jeopardized ischaemic regions. This process - ter med arteriogenesis - finally results in fully functional and structurally n ormal arteries which can ameliorate the ensuing detrimental effects of vess el obstruction in many regions of the body. Hallmarks of arteriogenesis are increased levels of shear forces (rather than ischaemia), the invasion of circulating monocytes land their pluripotent precursors), and the substrate s of arteriogenesis are pre-existing colateral arterioles. Copyright (C) 20 00 John Wiley & Sons, Ltd.