Coronary Endothelial Dysfunction and the Index of Microcirculatory Resistance as a Marker of Subsequent Development of Cardiac Allograft Vasculopathy.

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Cardiac allograft vasculopathy (CAV) is a leading cause of long-term morbidity and mortality after heart transplantation.1 Conventional methods for monitoring for CAV detect CAV after it has developed, which may be too late to modify its course. Endothelial dysfunction and the index of microcirculatory resistance (IMR) assessed soon after transplantation have both been shown in separate studies to predict development of CAV and long-term adverse outcome.2,3 The purpose of this study (URL: http://clinicaltrials.gov. Unique identifier: NCT01078363) is to quantify the combined impact of early endothelial dysfunction and elevated microvascular resistance as a marker of subsequent development of CAV at 1 year after cardiac transplantation. Forty-four heart transplant recipients underwent intracoronary acetylcholine injection (50–100 µg over 30 seconds), coronary physiology assessment, and volumetric intravascular ultrasound analysis performed in the left anterior descending coronary artery within 8 weeks after transplantation (baseline) and at 1 year. Endothelial dysfunction was defined as ≥20% change in diameter of the left anterior descending coronary artery as measured by quantitative angiography after acetylcholine and in comparison with baseline angiography.2 Elevated microvascular resistance was defined as an IMR≥20.3 IMR was assessed with a coronary pressure/thermistor-tipped wire …