The Impact of the Coronary Collateral Circulation on Outcomes in Patients With Acute Coronary Syndromes: Results From the ACUITY Trial
What is the prognostic implication of collateral circulation in patients presenting with acute coronary syndrome (ACS)?
The coronary collateral circulation was assessed by an independent angiographic core laboratory using the Rentrop Score in patients enrolled in the randomized ACUITY (Acute Catheterization and Urgent Intervention Triage Strategy) trial. The baseline characteristics and outcomes were compared between patients with visible collaterals (Rentrop score 1–3) and those without visible collaterals (Rentrop 0) in the vessel with the most severe stenosis.
The study cohort comprised 5,412 patients with moderate- to high-risk ACS. A total of 858 patients (16.0%) had visible collaterals, whereas 4,554 patients (84.0%) had no collaterals. The presence of collateral was not associated with any difference in clinical outcome at 1 year after multivariable adjustment major adverse cardiac events (MACE) (hazard ratio [HR], 0.94; 95% confidence interval [CI], 0.76-1.16; p = 0.55), mortality (HR, 1.03; 95% CI, 0.65-1.62; p = 0.91), myocardial infarction (MI) (HR, 1.07; 95% CI, 0.83-1.38; p = 0.60), and unplanned target vessel revascularization (TVR) (HR, 0.95; 95% CI, 0.71-1.28; p = 0.75). Similar results were observed in an analysis restricted to the subgroup of patients undergoing percutaneous coronary intervention (adjusted HR for MACE, 1.1; 95% CI, 0.76-1.61; p = 0.595), mortality (HR, 0.81; 95% CI, 0.10-6.44; p = 0.999), and MI (RR, 0.86; 95% CI, 0.54-1.35; p = 0.564). The presence of collaterals was associated with an increased risk of unplanned TVR (HR, 2.74; 95% CI, 1.48-5.10; p = 0.004).
The authors concluded that the presence of collateral circulation was not associated with any improvement in outcome of patients with ACS.
The results of this study are in contrast to prior work demonstrating improved outcomes in the presence of coronary collateral circulation. It is conceivable that the benefit of collateral circulation may be most pronounced in patients with stable coronary artery disease (CAD). It is also possible that presence of collaterals simply reflects the presence of more severe CAD, and thus, the presence of collateral may not overcome the implications of a greater burden of CAD when an ACS develops. Although, counterintuitive, this is the largest study on the subject to date, and it could well be that presence of collaterals in patients with ACS may indeed not make a difference in the outcome (other than perhaps permitting retrograde approach to a chronic total occlusion).
Keywords: Coronary Artery Disease, Myocardial Infarction, Acute Coronary Syndrome, Catheterization, Coronary Circulation, Constriction, Pathologic, Collateral Circulation, Percutaneous Coronary Intervention
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