Prognostic Value of Coronary Artery Calcium in the PROMISE Study (Prospective Multicenter Imaging Study for Evaluation of Chest Pain)

BACKGROUND: Coronary artery calcium (CAC) is an established predictor of future major adverse atherosclerotic cardiovascular events in asymptomatic individuals. However, limited data exist as to how CAC compares with functional testing (FT) in estimating prognosis in symptomatic patients. METHODS: In the PROMISE trial (Prospective Multicenter Imaging Study for Evaluation of Chest Pain), patients with stable chest pain (or dyspnea) and intermediate pretest probability for obstructive coronary artery disease were randomized to FT (exercise electrocardiography, nuclear stress, or stress echocardiography) or anatomic testing. We evaluated those who underwent CAC testing as part of the anatomic evaluation (n=4209) and compared that with results of FT (n=4602). We stratified CAC and FT results as normal or mildly, moderately, or severely abnormal (for CAC: 0, 1-99 Agatston score AS, 100-400 AS, and >400 AS, respectively; for FT: normal, mild=late positive treadmill, moderate=early positive treadmill or single-vessel ischemia, and severe=large ischemic region abnormality). The primary end point was all-cause death, myocardial infarction, or unstable angina hospitalization over a median follow-up of 26.1 months. Cox regression models were used to calculate hazard ratios (HRs) and C statistics to determine predictive and discriminatory values. RESULTS: <0.001). Overall discriminatory ability in predicting the primary end point of mortality, nonfatal myocardial infarction, and unstable angina hospitalization was similar and fair for both CAC and FT (C statistic, 0.67 versus 0.64). Coronary computed tomographic angiography provided significantly better prognostic information compared with FT and CAC testing (C index, 0.72). CONCLUSIONS: Among stable outpatients presenting with suspected coronary artery disease, most patients experiencing clinical events have measurable CAC at baseline, and fewer than half have any abnormalities on FT. However, an abnormal FT was more specific for cardiovascular events, leading to overall similarly modest discriminatory abilities of both tests. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01174550.