Coronary collaterals: an important and underexposed aspect of coronary artery disease.

Abstract

Important risk factors for cardiovascular disease (CVD) have been identified, but they fail to explain why some patients with atherosclerosis become symptomatic and have recurrent symptomatic disease, and others do not. Apart from the extent of coronary atherosclerosis (among other factors), the sensitivity of organs to episodes of ischemia is probably of importance. An organ may be less sensitive to episodes of ischemia if supplied with sufficient blood flow by well-developed collateral vessels. Unfortunately, some organs or even some individuals do not appear to have well-developed collateral vessels, if developed at all. At present, it is not clear why there are differences between individuals in their capability of developing a sufficient collateral circulation. The potential of individuals to develop coronary collateral circulation has so far been largely neglected but may play a major role in determining myocardial vulnerability. In the present article, we propose why coronary collaterals are important, and why this individual potential to develop collaterals should be considered an additional indicator of cardiac vulnerability. Also, we review determinants that play a role in collateral coronary blood supply. Coronary collaterals, or “natural bypasses,” are anastomotic connections without an intervening capillary bed between portions of the same coronary artery and between different coronary arteries (Figure 1).1 Collateral circulation potentially offers an important alternative source of blood supply when the original vessel fails to provide sufficient blood.2 Timely enlargement of collaterals may even avoid transmural myocardial infarction (MI) and death in symptomatic patients.3 As early as in 1956, Baroldi et al4 demonstrated the presence at birth of mostly corkscrew-shaped collaterals in normal human hearts, with a lumen diameter of 20 to 350 μm and lengths ranging from 1 or 2 cm to 4 or 5 cm. In hearts with typical findings of coronary disease at autopsy, …