Abstract 18654: Impaired Coronary Microvascular Function is Independently Associated with Fatal Cardiac Events at Long-term Follow-Up in Patients with Stable Coronary Artery Disease

Abstract

Background: Coronary microvascular dysfunction is increasingly recognized as an elementary component in the spectrum of coronary artery disease. Coronary flow velocity reserve (CFVR) is importantly determined by microvascular function, and may be considered a direct measure of microvascular function when measured in a reference coronary artery. We sought to determine the prognostic value of microvascular function, as assessed by measuring reference vessel CFVR (refCFVR), for long-term cardiac mortality. Methods: We studied consecutive patients with stable coronary artery disease in whom refCFVR was measured between April 1997 and September 2006 as part of ongoing study protocols. Patients underwent PCI of all ischemia causing lesions, as assessed by myocardial perfusion scintigraphy. Long term follow up was performed to document the occurrence of cardiac death. Results: RefCFVR was determined in 178 patients. During a median follow up of 11.6 years, 38 patients (15%) died of a cardiac cause. Kaplan Meier estimates of long term cardiac mortality showed a difference in mortality for high (≥3.0) and low (<3.0) refCFVR values (Figure). RefCFVR was additionally shown to be independently associated with cardiac mortality at long term follow up after multivariable adjustment (HR 0.432; 95% CI 0.213 - 0.876. P=0.02). Abnormal refCFVR was found to result from significantly lower baseline microvascular resistance, and a consequent increase in baseline flow velocity in patients with an abnormal refCFVR (6.96±2.54 mmHg/cm/s when refCFVR ≥3.0, versus 5.46±1.82 mmHg/cm/s when refCFVR <3.0; P<0.001). In contrast, hyperemic resistances, as well as flow velocities, were comparable between groups (P=NS for both). Conclusion: Impaired coronary microvascular is independently associated with long-term cardiac mortality in patients with stable coronary artery disease.