Coronary collaterals not visible by invasive angiography can provide more than half of normal resting perfusion in patients with coronary artery disease

Abstract

AbstractBackgroundThere is sufficient collateral flow to prevent myocardial ischemia during balloon occlusion in approximately one in five patients. However, the magnitude of myocardial perfusion provided by the coronary collateral circulation during occlusion is unknown. Therefore, the aim of this study was to quantify collateral myocardial perfusion during balloon occlusion in patients with coronary artery disease (CAD).MethodsPatients without angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 hours after PTCA.ResultsThe study included 21 patients (median [interquartile range] age 70 [56-74] years, 48% female). The diameter stenosis ranged from 60-99%, with successful PTCA performed with a mean 5-minute balloon occlusion. The perfusion defect extent was 16 [8-30]% of the LV. The collateral perfusion at rest was 64 [58-68]% of normal perfusion. Collateral perfusion was negatively correlated with perfusion defect size (R2=0.85, p<0.001), and did not differ by sex (p=0.27) or age (p=0.58).ConclusionsThis is the first study to describe the magnitude of coronary microvascular collateral perfusion in patients with CAD. On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provide approximately 60% of the perfusion that reaches the jeopardized myocardium during coronary occlusion.