Importance of collateral circulation in coronary heart disease.

AIMS Collateral arteries are a common but inconsistent finding in coronary heart disease (CHD). We endeavoured to review the methods for coronary artery collateral assessment, the predictors and clinical importance of collateral blood flow, and the potential for therapeutic augmentation of collateral anastomoses. METHODS AND RESULTS While many methods have been used to assess collateral blood flow only a few have been formally validated. Collateral flow index, as determined by measurement of intra-coronary pressure or flow velocity, is the most robust measure of collateral flow. These techniques have led to important advances in our understanding of collateral artery function. Coronary collateral arteries may prevent myocardial ischaemia in healthy subjects and in patients with CHD. A functional collateral circulation may lead to reduced ischaemia, preservation of ventricular function, and an improved prognosis. Recent trials have demonstrated that vascular progenitor cell therapies may improve ventricular function following acute myocardial infarction, raising the possibility of effective biological treatments to improve myocardial blood flow and prognosis in CHD. CONCLUSIONS Coronary collateral anastomoses represent a prognostically important adaptive response in patients with CHD. Therapeutic augmentation of collaterals with emerging biological therapies represents a desirable goal for treating CHD patients.