Assessing Coronary Calcium Thresholds on Attenuation-Correction CT With Myocardial Perfusion Imaging Equating to Secondary Prevention

BACKGROUND: Patients with a coronary artery calcium (CAC) score >300 on dedicated CAC scoring computed tomography (CT) are at equivalent risk of major adverse cardiac events (MACE) as those with established atherosclerotic cardiovascular disease (ASCVD). OBJECTIVES: The aim of the study was to identify the extent of CAC on CT performed for attenuation correction (CTAC) as part of nuclear myocardial perfusion imaging that equates to secondary prevention. METHODS: We retrospectively studied 17,901 patients (48% female, age 64 ± 12 years, body mass index 30 kg/m2 [26-36]) who underwent nuclear myocardial perfusion imaging with CTAC (single photon emission computed tomography/CT or positron emission tomography/CT) at a single center. Prior ASCVD was defined as myocardial infarction (MI), cerebrovascular accident, peripheral artery disease, or prior revascularization. A semiquantitative visually estimated CAC score was obtained by scoring CAC in each coronary artery from 0 (absent) to 3 (severe), yielding a total score of 0 to 12 (zero, mild 1-2, moderate 3-6, and severe ≥7). The primary outcome was the composite of death, MI, or late revascularization. RESULTS: Among 13,852 patients without prior ASCVD (CAC zero 45%, mild 23%, moderate 21%, severe 11%) and 4,049 with ASCVD, 2,006 patients (11%) experienced MACE during a median follow-up of 25 (Q1-Q3: 10-43) months. In multivariable Cox regression, patients with severe calcification had no difference in risk for MACE, MI, or all-cause mortality vs ASCVD patients (P > 0.05). CONCLUSIONS: Patients without prior ASCVD but with severe CAC (score ≥7) on CTAC demonstrated a risk for cardiovascular events and mortality comparable to those with known ASCVD, highlighting the need for more aggressive management in this high-risk primary prevention group.