Background: The recruitment of coronary collateral vessels results from an endogenous adaptation to ischemic heart disease (IHD). Presence of collaterals may exert protection at the time of acute or chronic obstructive coronary disease. The protective role of collaterals in patients with extensive coronary artery disease however, has been disputed. We examined the effects of coronary collateral circulation on cardiovascular outcomes, with an emphasis on clinical prognostic value and on a putative role of IHD burden.
Methods: Data analyzed were obtained in the REGRESS study, involving 879 male participants undergoing coronary angiography and being followed for 24 months. Presence of coronary collaterals spontaneously visible on angiography was assessed. Events included: myocardial infarction (MI), coronary heart disease death and percutaneous or surgical coronary intervention. Estimates of relative risks of outcome events were calculated using proportional hazard analysis, with adjustments for confounding factors and stratification for initial revascularization strategy and factors reflecting extent of IHD burden.
Results: Event-free survival after two years was 84% in patients without collaterals, and 92% in patients with collaterals (p=0.0020). The crude HR was 0.48 (95% CI: 0.30-0.77), and 0.38 (0.23-0.65) after adjustment for confounders and cardiovascular risk factors. The protective effect of coronary collaterals was not modified by the extent of IHD burden (interaction p=0.99).
Conclusion: The angiographical presence of coronary collaterals is a clinical predictor of cardiovascular prognosis. Collaterals exert a protective effect on outcome in a broad spectrum of patients. Our data suggest that this protective effect is independent of disease burden, and remains present in patients with extensive IHD.