Coronary Artery Imaging: State of the Evidence for Primary Prevention

August 26 - 27, 2019
NIH, Porter Neuroscience Building, Room 640, Bethesda MD


The National Heart, Lung, and Blood Institute (NHLBI) convened a workshop of multidisciplinary experts in areas of cardiovascular epidemiology, coronary imaging, clinical trials, and clinical practice.  After reviewing the state of the evidence for coronary artery imaging in risk assessment, working group members deliberated on considerations for potential designs of clinical trials to address current gaps in knowledge. 


A large number of myocardial infarction, stroke, and heart failure events occur in the United States as the result of long term exposure to elevated atherogenic blood lipid levels. Many of these cardiovascular events occur in individuals without pre-existing clinical cardiovascular disease (CVD).  Since atherogenic blood lipid levels can be lowered significantly with drugs in most individuals, recent guidelines have based treatment recommendations on identifying individuals with sufficient risk-to-benefit from drug treatment within a 10-year period (see the 2018 AHA/ACC Multisociety Guideline on the Management of Blood Cholesterol and 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease). These guidelines recommend statin treatment for high-risk individuals with 10-year CVD risk ≥20%. They also recommend consideration of, or the initiation of, statin treatment for those at intermediate risk (estimated CVD risk of 7.5% to 19.9%) and select individuals at borderline risk (5-7.5%) after a clinician-patient discussion and in the context of considering additional clinical risk-enhancing factors.

These guidelines have based their CVD risk assessment on the 2013 Pooled Cohort Equation (PCE). The PCE is based on a combination of data from five cohorts and is used to estimate the 10-year primary risk of atherosclerotic CVD among patients without pre-existing clinical CVD who are between 40 and 75 years of age (2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk). However, the guidelines acknowledge that in many cases, assessment of atherosclerotic CVD risk may still be uncertain even after assessment of PCE and consideration of risk-enhancing factors. In these cases, the guideline authors concluded that the use of coronary artery calcium (CAC) is reasonable as a shared-decision making tool to guide risk-based decisions for initiation of statin therapy for those at intermediate or selected borderline risk.  Epidemiological research has concluded that CAC screening by non-contrast computed tomography (CT) improves the accuracy of the 2013 PCE and other similar risk assessment tools (Nasir K, et al., JACC 2015;66:1657-68;Valenti  et al., Int J Cardiol. 2015 May 6; 187:534-540). 

A wide range of CVD guidelines over the last decade have considered the role of CAC in risk assessment and in decision making about the use of statins in the primary prevention of CVD. When comparing the recent aforementioned AHA/ACC guidelines with recommendations from other major professional societies, there is no agreement in the role of CAC screening among these guidelines. This is largely because there is a lack of definitive randomized clinical trial evidence to show that CAC screening is a superior strategy for CVD risk assessment and prevention compared to traditional risk assessment without CAC. Barriers to the conduct of such trials have been the large sample size needed and the lack of consensus that this is a very high priority question. The recent enhancement of the state of the art of pragmatic trials by the NIH Collaboratory and the creation of larger networks and cohorts like PCORNET may make large scale prevention trials more feasible.