Coronary Artery Calcium Scoring Does Not Add Prognostic Value to Standard 64-Section CT Angiography Protocol in Low-Risk Patients Suspected of Having Coronary Artery Disease

Coronary CT angiography (CCTA) and Coronary Artery Calcium Scoring (CACS) have been validated as means to predict adverse cardiac outcomes (i.e., cardiac death or myocardial infarction) in low-risk patients. This single-center retrospective cohort study sought to evaluate which imaging modality had the highest predictive value. The authors enrolled 4338 patients aged > 30 years with no known coronary artery disease (CAD) and new symptoms and risk factors for CAD. Each patient underwent CCTA and CACS by standard imaging protocols, and the amount of radiation exposure was calculated. Two independent radiologists determined the CACS and level of CAD was categorized into non-obstructive and by one-, two-, or three-vessel disease, based on CT imaging. Patients were followed by electronic medical record review or telephone interviews for an average of 828 days ± 380 days for the clinical outcomes of cardiac death, non-fatal myocardial infarction (MI), unstable angina requiring hospitalization, or revascularization. This study found that patients with clinical CAD tended to have risk factors of increased age, male gender, history of hypertension, diabetes, and dyslipidemia, with a significantly higher CACS and a higher amount of CAD seen on CCTA. A total of 3% of patients developed an outcome event. The authors noted that CACS was not an independent predictor of any cardiac outcome, but the presence of CAD on CCTA was. Additionally, both a CACS of > 400 or two- to three-vessel CAD on CTTA had an 80% or less event-free survival rate. Overall, CAC scores were more predictive than patient history-based risk factors for predicting adverse events, but there was no difference in combining CACS with CCTA in predicting adverse outcomes than CCTA alone, which was higher than CACS alone. The authors concluded that CCTA is a better predictor of adverse cardiac outcomes than CACS. In addition, there is no increase in predictive value from adding CACS with CCTA and that by doing CCTA alone, radiation exposure could be limited, though in comparison, CACS has a significantly lower 1.8 mSV vs. 8.8 mSV average amount of radiation.