Comparison of the Coronary Artery Calcium Score and Number of Calcified Coronary Plaques for Predicting Patient Mortality Risk

Multiple coronary artery calcium (CAC) parameters have recently been proposed to improve risk prediction in patients with intermediate clinical risk based on CAC scoring, but outcome data that assess these variables are relatively sparse. We analyzed data from 11,633 consecutive asymptomatic patients undergoing CAC scanning that were followed for 8.8 ± 3.5 years for all-cause mortality (ACM). The patients who had coronary artery calcification were grouped by the number of calcified coronary plaques: 0, 1 to 5, 6 to 20, and >20 plaques. We examined the independent prognostic value of plaque number and its synergistic prognostic value when added to the CAC score. We observed a stepwise increase in ACM with increasing plaque number. In patients with a CAC score of 1 to 99, 6 plaques or more were associated with increased mortality. In patients with CAC scores of 100 to 399, there was a stepwise increase in ACM with increasing plaque number. For CAC >400, the risk of ACM was high regardless of plaque number. After risk adjustment, the number of plaques was a significant predictor of risk for ACM in the patients with an intermediate CAC score. In these patients, additional consideration of plaque number improved net reclassification improvement for predicting ACM by 29%. In conclusion, the number of calcified plaques adds to risk stratification beyond the CAC score in patients with intermediate CAC scores.