Prognostic Value of Coronary Artery Calcium Scoring in Addition to Single-Photon Emission Computed Tomographic Myocardial Perfusion Imaging in Symptomatic Patients

Background-The prognostic value of coronary artery calcium (CAC) scoring on top of myocardial perfusion imaging with single-photon emission computed tomography (SPECT) in patients suspected for coronary artery disease is not well established. Methods and Results-Four thousand eight hundred ninety-seven symptomatic patients without a history of coronary artery disease referred for SPECT and CAC scoring were included. Major adverse cardiac events (MACEs) were defined as late revascularization (>90 days after scanning), nonfatal myocardial infarction, and all-cause mortality. The frequency of abnormal SPECT increased with higher CAC scores, from 12% in patients with CAC scores of 0 to 19%, 32%, 37%, and 50% among those with CAC scores 1 to 99, 100 to 399, 400 to 999, and >= 1000, respectively (P<0.001). During a median follow-up of 940 days (25th to 75th percentile, 581-1377), a total of 278 MACEs were observed. Overall incidence of MACE was 2.3% per year. A stepwise increase of MACE was present with increasing CAC scores, both in patients with normal SPECT (annual event rate CAC score 0: 0.6%; CAC score >= 1000: 5.5%) and abnormal SPECT (annual event rate CAC score 0: 0.4%; CAC score >= 1000: 7.6%). After multivariate analysis, both SPECT and CAC score were independent predictors of MACE (CAC score >= 1000: hazard ratio, 7.7; P<0.001 and large perfusion defect on SPECT: hazard ratio, 3.7; P<0.001). Conclusions-CAC score and SPECT are independent predictors of MACE in patients suspected for coronary artery disease. Our findings strongly support performing a CAC score in addition to SPECT in symptomatic patients to better define the risk of events during follow-up.