1. From this cohort study of long-term mortality in asymptomatic adults, coronary artery calcification (CAC) effectively predicted long-term (15-year) all-cause mortality after adjusting for other cardiac risk factors.
Evidence Rating Level: 2 (Good)
Study Rundown: Heart disease is the leading cause of death in Americans, and accurate prediction of risk of death from heart disease could help guide preventive management. Coronary artery calcification (CAC)—a reflection of disease in arteries that supply the heart—has been shown to be associated with short-term outcomes in patients without symptoms of heart disease. This study sought to examine CAC as a predictor of long-term (15-year) mortality among these patients. Overall, patients with more CAC were at higher risk of death than patients with lower CAC. After accounting for several known risk factors for heart disease, such as hypertension, high cholesterol, diabetes and smoking, CAC was found to be highly predictive of time to death. Furthermore, when CAC was added to a model predicting death among patients without symptoms, the model’s ability to predict death improved. Notably, this study was limited in that it did not compare the predictive model using CAC with existing clinical tools that are in widespread use to anticipate adverse outcomes from heart disease, such as the Framingham risk score. In addition, unlike markers such as blood pressure or cholesterol, CAC score requires patients to undergo a CT scan and is currently not recommended for low-risk, asymptomatic patients. Nevertheless, this study suggests that screening patients for CAC may help guide patients and providers about risk of long-term but nonetheless premature death.
In-Depth [prospective cohort]: This observational cohort study evaluated CAC scoring in 9715 patients from the area surrounding Nashville, Tennessee. All patients were asymptomatic by self-report. After adjusting for known risk factors for coronary artery disease (CAD), CAC was highly predictive of all-cause mortality by 15-years of follow-up (p<0.001 by Cox proportional hazard modeling). There was a graded relationship between CAC score and all-cause mortality, with increased CAC score associated with greater risk of mortality at 10 and 15 years. CAC also successfully stratified patients within risk groups that had been determined using traditional risk factors for coronary artery disease. Furthermore, approximately 40% of patients who died but who were deemed low- or intermediate-risk by the traditional CAD risk factor model were reclassified as high-risk when CAC was included in the model. Notably, a large proportion of patients who survived the study follow-up period were also re-classified as high-risk when CAC was included. Comparisons with existing risk-prediction scores, as well as risk-benefit analyses given the potential harms from CT scanning, will be needed to further define the role of CAC scoring in clinical practice.
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