Noncalcified Atherosclerotic Plaque Burden at Coronary CT Angiography: A Better Predictor of Ischemia at Stress Myocardial Perfusion Imaging Than Calcium Score and Stenosis Severity

OBJECTIVE. The purpose of this study was to examine the relation between the coronary CT angiographic findings of calcified and noncalcified plaque burden and stenosis severity and the myocardial perfusion imaging finding of ischemia. MATERIALS AND METHODS. Seventy-two patients (41 men, 31 women; mean age, 56 years) underwent coronary CT angiography and stress-rest SPECT myocardial perfusion imaging. Calcium scoring was performed. Coronary CT angiograms were analyzed for stenosis and noncalcified or mixed plaque. A plaque analysis tool was used to calculate the volume of noncalcified plaque components. SPECT images were analyzed for perfusion defects. Data were analyzed per patient and per vessel. RESULTS. A total of 53 purely noncalcified, 50 mixed, and 201 purely calcified plaques were detected. Forty-five stenoses were rated >= 50%, 19 of those being >= 70%. Myocardial perfusion imaging depicted perfusion defects in 37 vessels (13%) in 24 patients (18 reversible, 19 fixed defects). Vessels with >= 50% stenosis had significantly (p = 0.0009) more perfusion defects in their supplied territories (11 with, 22 without perfusion defects) than did vessels without significant lesions (26 with, 229 without perfusion defects). In vessel-based analysis, the sensitivity of coronary CT angiography in prediction of any perfusion defect on myocardial perfusion images was 30% with 91% specificity, 33% positive predictive value, and 90% negative predictive value. Between vessels with and those without perfusion defects, there was no significant difference in Agatston or calcium volume score (p = 0.25), but there was a significant difference in noncalcified plaque volume (44 +/- 77 vs 19 +/- 58 mm(3); p = 0.03). Multiple stepwise regression analysis showed noncalcified plaque volume was the only significant predictor of ischemia (p = 0.01). CONCLUSION. At coronary CT angiography, noncalcified plaque burden is a better predictor of the finding of myocardial ischemia at stress myocardial perfusion imaging than are calcium score and degree of stenosis.