In this prospective multicenter trial of chest pain patients without known CAD, 64-multidetector row CCTA possesses high diagnostic accuracy for detection of obstructive coronary stenosis at both thresholds of 50% and 70% stenosis. Importantly, the 99% negative predictive value at the patient and vessel level establishes CCTA as an effective noninvasive alternative to ICA to rule out obstructive coronary artery stenosis. (A Study of Computed Tomography [CT] for Evaluation of Coronary Artery Blockages in Typical or Atypical Chest Pain; NCT00348569).

Background-Coronary endothelial dysfunction may be an early marker for cardiac allograft vasculopathy (CAV) in orthotopic heart transplant recipients. Using serial studies with intravascular ultrasound and Doppler flow-wire measurements, we have previously demonstrated that annual decrements in coronary endothelial function are associated with progressive intimal thickening. The present study tested whether endothelial dysfunction predicts subsequent clinical events, including cardiac death and CAV development. Methods and Results-Seventy-three patients were studied yearly beginning at transplantation until a prespecified end point was reached. End points were angiographic evidence of CAV (Ͼ50% stenosis) or cardiac death (graft failure or sudden death). At each study, coronary endothelial function was measured with intracoronary infusions of adenosine (32-g bolus), acetylcholine (54 g over 2 minutes), and nitroglycerin (200 g) into the left anterior descending coronary artery; intravascular ultrasound images and Doppler velocities were recorded simultaneously. Of the 73 patients studied, 14 reached an end point during the study (6 CAV and 8 deaths, including 4 with known CAV, 1 graft failure, and 3 sudden). On the last study performed, the group with an end point had decreased epicardial (constriction of 11.1Ϯ2.9% versus dilation of 1.7Ϯ2.2%, Pϭ0.01) and microvascular (flow increase of 75Ϯ20% versus 149Ϯ16%, Pϭ0.03) endothelium-dependent responses to acetylcholine compared with the patients who did not reach an end point.Responses to adenosine and nitroglycerin did not differ significantly. Conclusions-Endothelial

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