Coronary Artery Calcium Score and Risk Classification for Coronary Heart Disease Prediction

Abstract

Context Coronary artery calcium score (CACS) has been shown to predict future coronary heart disease (CHD) events. However, the extent to which adding CACS to traditional CHD risk factors improves classification of risk is unclear. Objective To determine whether adding CACS to a prediction model based on traditional risk factors improves classification of risk. Design, Setting and Participants CACS was measured by computed tomography on 6,814 participants from the Multi-Ethnic Study of Atherosclerosis (MESA), a population-based cohort without known cardiovascular disease. Recruitment spanned July 2000 to September 2002; follow-up extended through May 2008. Participants with diabetes were excluded for the primary analysis. Five-year risk estimates for incident CHD were categorized as 0-<3%, 3-<10%, and ≥10% using Cox proportional hazards models. Model 1 used age, gender, tobacco use, systolic blood pressure, antihypertensive medication use, total and high-density lipoprotein cholesterol, and race/ethnicity. Model 2 used these risk factors plus CACS. We calculated the net reclassification improvement (NRI) and compared the distribution of risk using Model 2 versus Model 1. Main Outcome Measures Incident CHD events Results Over 5.8 years median follow-up, 209 CHD events occurred, of which 122 were myocardial infarction, death from CHD, or resuscitated cardiac arrest. Model 2 resulted in significant improvements in risk prediction compared to Model 1 (NRI=0.25, 95% confidence interval 0.16-0.34, P<0.001). With Model 1, 69% of the cohort was classified in the highest or lowest risk categories, compared to 77% with Model 2. An additional 23% of those who experienced events were reclassified to high risk, and an additional 13% without events were reclassified to low risk using Model 2. Conclusions In the MESA cohort, addition of CACS to a prediction model based on traditional risk factors significantly improved the classification of risk and placed more individuals in the most extreme risk categories.

2016 SCCT/STR guidelines for coronary artery calcium scoring of noncontrast noncardiac chest CT scans: A report of the Society of Cardiovascular Computed Tomography and Society of Thoracic Radiology

“…26 It has outperformed risk factor based paradigms such as the Framingham Risk Score (FRS), 3 the European Society of Cardiology Score 4 and the 2013 AHA/ACC Pooled Cohort Equations, 5 and, in 3 prospective, population-based outcome trials demonstrated an extremely high net reclassification index (NRI) of the FRS, ranging from 52% to 66% in the intermediate risk group. 16,27,28 The inclusion of CAC in guidelines is summarized in Table 2. Formal recognition of the power of CAC occurred in 2010, 10 30 Subsequently, the 2013 ACC/AHA Guideline on the Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults assigned a class IIb (may be considered) recommendation to CAC, and recommended its use in patients in whom the Pooled Cohort Equation risk decision was unclear.…”

“…Those at very low risk and those at very high risk have not been considered ideal candidates, since the results of the calcium scan will change their risk status less often (12e16% for low risk, and 34% for high risk) than for intermediate risk patients (56%). 16,27,28 However, since the information is in every scan irrespective of the indication for the NCCT examination, it appears prudent to report it irrespective of the scan indication. The usual concepts of inclusion and exclusion criteria do not apply since cardiac risk assessment is never the primary indication for a NCCT examination.…”

Cardiovascular Event Prediction and Risk Reclassification by Coronary, Aortic, and Valvular Calcification in the Framingham Heart Study

“…Development and progression of atherosclerosis are strongly associated with major cardiovascular risk factors. Subclinical atherosclerosis manifesting as coronary artery calcification (CAC) is associated with future coronary heart disease (CHD), independent of traditional risk factors, and CAC improves discrimination and classification of CHD risk overall and in persons at intermediate risk by placing more persons in the most extreme risk categories 3, 4. Similar associations with incident CHD and/or CVD have been reported for noncoronary calcifications including the thoracic and abdominal aorta using either plain radiographs5, 6, 7, 8, 9 or computed tomography (CT) scans10, 11, 12 and for aortic sclerosis using echocardiography 13.…”

Imaging Cardiovascular Calcification

“…It predicts future cardiovascular risk beyond the traditional Framingham risk score alone 29, 30, 31, 32. An elevated CACS may portend an increased risk of cardiovascular events in some patients 33.…”