Use of cardiac CT and calcium scoring for detecting coronary plaque: implications on prognosis and patient management

Clinicians often use risk factor-based calculators to estimate an individual''s risk of developing cardiovascular disease. Non-invasive cardiovascular imaging, particularly coronary artery calcium (CAC) scoring and coronary CT angiography (CTA), allows for direct visualization of coronary atherosclerosis. Among patients without prior coronary artery disease, studies examining CAC and coronary CTA have consistently shown that the presence, extent and severity of coronary atherosclerosis provide additional prognostic information for patients beyond risk factor-based scores alone. This review will highlight the basics of CAC scoring and coronary CTA and discuss their role in impacting patient prognosis and management.Coronary artery disease (CAD) is the leading cause of morbidity and mortality in most industrialized nations throughout the world.¹ Given the burden of coronary heart disease (CHD) to patients and society as a whole, much work has been carried out to determine patients'' risk of adverse cardiovascular events. Such risk estimations are important as they often inform the need for preventive therapies such as lipid-lowering medications and aspirin. For instance, the Framingham risk score (FRS) uses age, gender, total cholesterol, high-density lipoprotein cholesterol, smoking status, systolic blood pressure and blood pressure treatment status to estimate 10-year risk of a myocardial infarction in patients without heart disease or diabetes.² More recently, the 2013 American College of Cardiology/American Heart Association (ACC/AHA) guidelines on treatment of blood cholesterol identified four groups of individuals who may potentially benefit from statin therapy: patients with known atherosclerotic cardiovascular disease (ASCVD), low-density lipoprotein cholesterol ≥190 mg dl⁻¹, diabetes and a ≥7.5% estimated 10-year risk of developing ASCVD determined by a risk calculator.³ However, these guidelines also suggest that in selected individuals not in the aforementioned groups, and for whom a decision to initiate statin therapy is otherwise unclear, additional risk factors such as a coronary artery calcium (CAC) score of ≥300 Agatsiton units or ≥75th percentile for age, sex and ethnicity can be considered.³ The European Society of Cardiology also included CAC in its 2012 European Guidelines on cardiovascular disease (CVD) prevention by stating that CAC should be considered for cardiovascular risk assessment in asymptomatic adults at moderate risk (3–6

Table 1.

Recommendations for coronary artery calcium testing according to recent guidelines

Guideline	Recommendations for CAC testing
2013 American College of Cardiology/American Heart Association Guidelines3,4	IIb indication; level of evidence B “if, after quantitative risk assessment, a risk-based treatment decision is uncertain, assessment (of CAC) may be considered to inform treatment decision making.”a
2012 European Society of Cardiology Guidelines5	IIa indication; level of evidence B “(CAC) should be considered for cardiovascular risk assessment in asymptomatic adults at moderate risk”
2010 Appropriate Use Criteria for Cardiac CT6
Appropriate	Intermediate risk OR low risk and family history of premature CADb
Inappropriate	Low risk AND no family history of premature CADb
Uncertain	High risk

Open in a separate windowCAD, coronary artery disease; ASCVD, atherosclerotic cardiovascular disease; LDL-C, low-density lipoprotein cholesterol.^aAfter discussion with patient when decision to initiate statin therapy is unclear among selected individuals who are not in one of the four statin benefit groups, defined as those with (i) clinical atherosclerotic cardiovascular disease, (ii) primary elevation of LDL-C ≥190 mg dl⁻¹, (iii) age of 40–75 years with diabetes and LDL-C of 70–189 mg dl⁻¹ or (iv) age of 40–75 years without clinical ASCVD or diabetes and LDL-C of 70–189 mg dl⁻¹ and estimated 10-year ASCVD risk ≥7.5%.^bFirst-degree relative male <55 years of age or female <65 years of age.The use of imaging to directly measure the burden of atherosclerosis can provide a more personalized risk assessment than using risk factor-based calculators. CAC scoring can be used to determine the actual presence and extent of calcified coronary artery plaque, whereas coronary CT angiography (CTA) visualizes calcified and non-calcified plaque, as well as the severity of luminal stenosis. While CAC testing is most commonly performed for risk assessment in asymptomatic individuals, coronary CTA is commonly performed in patients who have symptoms suggestive of underlying CHD. This review will discuss these two imaging modalities and how to use the results of these tests in patient management.