The correct answer is: B. Maximize risk factor modification by starting a low-dose aspirin and statin therapy.

Atherosclerosis is necessary for nearly all coronary events. The development of atherosclerosis is multifactorial. There is significant heterogeneity in the contribution of common traditional modifiable risk factors including apolipoprotein B (apoB)-containing lipoproteins, smoking, diabetes, hypertension, and sedentary lifestyle to atherogenesis.¹ In participants from the Multi-Ethnic Study of Atherosclerosis (MESA) without atherosclerosis as measured by coronary artery calcium (CAC), even the presence of multiple modifiable risk factors was associated with low event rates (3.1%). In contrast, in those with elevated CAC and no modifiable risk factors, the event rates were significantly higher at nearly 11%.¹

While risk estimators are improving in accuracy,^2,3 the presence of subclinical atherosclerosis (primarily by CAC) has consistently been an additive predictor of coronary events in individuals and further discriminates between those at higher and lower risk for events.^4-6 The case patient is at elevated risk because of the burden of subclinical atherosclerosis and, therefore, answer choice A is incorrect.

The recent 2013 ACC/AHA guidelines on cholesterol treatment take a risk-based approach to recommendations for statin therapy.⁷ The patient in this case has a low estimated 10-year risk at 3.7%. The current guidelines suggest a risk discussion in this case based on the patient's family history of premature coronary heart disease (CHD). Subclinical atherosclerosis imaging by CAC scanning can help with this discussion.⁸

Recently, eight-year follow-up from the Dallas Heart Study showed that among participants with a family history of MI, those without CAC experienced a significantly lower CHD event rate of 1.9% compared to 8.8% in those with any CAC.⁹ The case patient has a CAC score >100 that places him above the 75th percentile for his age, gender, and ethnicity. We would recommend moderate- or high-intensity statin therapy during a risk discussion based on an estimated 10-year event rate that exceeds 7.5%. Furthermore, recent data support the use of aspirin in those with CAC >100. Therefore, answer choice B is the correct answer.

Subclinical atherosclerosis imaging with CAC scanning has been endorsed by several committees to assist with risk assessment. The 2010 ACC/AHA risk assessment guidelines gave CAC scanning a IIA recommendation in those deemed to be at intermediate risk for CHD events.¹¹ In the 2010 appropriate use criteria for cardiac CT endorsed by multiple societies, CAC scanning was deemed appropriate among low-risk asymptomatic patients with a family history of premature CHD in addition to those at intermediate risk.¹² Most recently, the 2013 ACC/AHA risk assessment guidelines gave CAC scoring a IIB recommendation. Specifically, the committee suggests that if there is uncertainty about whether to start pharmacotherapy after risk estimation, then CAC scoring could be considered.²

An important consideration in this case is the use of CTA to identify subclinical atherosclerosis. While coronary CTA is a more specific and sensitive test for atherosclerosis, there is no evidence that CTA adds significantly to CAC scanning in an asymptomatic population. However, CTA may identify vulnerable features of plaque that are not picked up by CAC scanning, such as those present in the case example.¹³ Motoyama et al. identified high-risk features for acute coronary syndromes (ACS) in asymptomatic subjects on CTA including positive remodeling and low-attenuation plaque, in addition to spotty calcification in those presenting with ACS.^14,15 A small preliminary study suggested a benefit of statin therapy on plaque volume and the amount of low-attenuation plaque.¹⁶ The role of CTA in asymptomatic, primary prevention patients is actively under investigation.¹⁷ The benefits of CTA should be weighed against exposure to contrast, expense, and the need to train readers. With rapidly advancing technology, CTAs can now be performed with the equivalent radiation exposure of two mammograms.¹⁸

Currently, the use of CTA is useful in appropriate symptomatic patients, particularly in chest pain protocols in the emergency department.¹⁹ Many of these patients have mild or moderate, non-obstructive atherosclerosis that is unlikely to be the cause of their presenting symptoms, but should be managed with aggressive preventive therapies. In symptomatic patients from the CONFIRM registry, there is an increased hazard of mortality in those with non-obstructive atherosclerosis on CTA compared to those without atherosclerosis on CTA.²⁰

Some have advocated for stress testing in those with CAC scores > 400; however, the patient in this case does not meet this criteria.^21,22 Therefore, answer choices C and D are incorrect as the patient is asymptomatic.

References

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17. U.S. National Institutes of Health.Detection of Subclinical Atherosclerosis in Asymptomatic Individuals (Decide CTA). (ClinicalTrials.gov website). 2009-2014. Available at: http://clinicaltrials.gov/ct2/show/NCT00862056?term=DECIDE-CTA. Accessed June 22, 2014.
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