Role of Coronary Calcium Scoring in the Assessment of Physiological Ischemia in Patients with Intermediate Stenosis

Abstract

Although coronary artery calcium (CAC) is an established marker of coronary atherosclerosis, whether it also reflects the physiological significance is unknown. This study aims to evaluate if CAC could indicate physiological ischemia in intermediate stenosis defined by an invasive fractional flow reserve (FFR). CAC score (CACS) derived from either whole coronary arteries or individual arteries was measured by computed tomography among patients with intermediate de novo lesions (percent diameter stenosis from 30% to less than 70%). All stenoses were evaluated by invasive FFR; lesions with an FFR ≤ 0.80 were considered significant. We enrolled 119 patients with 143 lesions. Of these, 42 lesions (29.4%) demonstrated significant ischemia by FFR measurement. FFR values had modest but significant correlations with CACS in individual arteries with intermediate stenosis (r = - 0.290; p < 0.001). A receiver operating characteristic curve analysis showed that CACS of individual arteries with intermediate stenosis had 71.4% sensitivity and 67.3% specificity as a predictor of significant ischemia at a cut off value of 145.9. Multivariable analysis showed that percent diameter stenosis and CACS in individual arteries with intermediate stenosis were independent predictors for significant ischemia. By net reclassification improvement analysis, CACS in individual arteries with intermediate stenosis provided incremental prediction for significant ischemia over minimum lumen diameter, percent diameter stenosis, and lesion length. CACS measured in each artery, but not the total CACS, provides additional information as to whether an angiographically intermediate stenosis within the artery is significant enough to cause myocardial ischemia.