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Precision Medicine
Importance of the Coronary Artery Calcium (CAC) Score in Risk Assessment and Prevention of Atherosclerotic Cardiovascular Disease
According to the Centers for Disease Control and Prevention (CDC), one individual dies every thirty-six seconds in the United States from cardiovascular disease- the number one cause of death in the United States and a major cause of death globally. Specifically, atherosclerotic cardiovascular disease (ASCVD), which is caused by buildup of plaques in arterial walls can be potentially prevented by the aid of the coronary artery calcium (CAC) score.
In general, it can be difficult to predict an ASCVD event. Traditional risk factors including age, weight, blood pressure and cholesterol levels suggest some risk, but they are insufficient in accurately predicting ASCVD risk in asymptomatic individuals. There is a great need for accurate estimation and prediction of ASCVD risk to minimize cost and misallocation of health care resources.
In a recent review published in the British Medical Journal, Houston Methodist cardiologists Khurram Nasir, MD, MPH, Jerold B. Katz Investigator and Professor of Cardiology and Miguel Cainzos-Achirica, MD, PhD, MPH, Assistant Professor of Preventive Cardiology, discuss the history of the CAC score, key studies leading to its adoption in clinical practice guidelines and its role in the personalization of risk scoring and subsequent management strategies.
Using relatively inexpensive, low-radiation, non-contrast computed tomography scans, the CAC scores can detect and quantify the coronary atherosclerotic plaque. Today, more than 30 years after the inception of the score, there is ample support to continue using CAC as a decision aid when prescribing statins and potentially other preventive medications and interventions.
The CAC score offers critical insight for downstream decision-making and disease management strategies. Notably, that could mean refraining from, or at least delaying, expensive novel therapies, especially if the patient’s calcium score is zero.
Patients with a CAC count of zero have incredibly low rates of cardiovascular events during follow-up — or at least the lowest among their cohort. For instance, a 75-year-old patient with a score of zero does not have zero risk of cardiac events but is within the lowest risk category for their age and markedly lower risk than a 75-year-old with a high score. The same applies to patients with diabetes, severe hypercholesterolemia and other features that increase the average risk of cardiovascular events.
Khurram Nasir, MD, MPH
Professor of Cardiology at
Houston Methodist
Miguel Cainzos-Achirica, MD, PhD, MPH
Assistant Professor of Preventive Cardiology at Houston Methodist
In a context of progressively low estimated ASCVD risk thresholds for consideration of preventive therapy with statins in international primary prevention guidelines, CAC=0, which is associated with low event rates in several populations, has become a particularly powerful prognostic tool and may be incorporated in clinician-patient discussions to guide the safe avoidance of preventive therapy with statins and aspirin. Moving forward, ongoing studies will help define the potential role of CAC informing the personalized allocation of other risk reduction therapies among several populations, such as individuals with diabetes and severe hypercholesterolemia.”
Khurram Nasir, MD, MPH
Professor of Cardiology at Houston Methodist
How long that protection lasts is a subject of ongoing debate and research, though Nasir and Cainzos-Achirica recommend that patients with a CAC score of zero get their levels rechecked every three to five years.
Having a CAC of zero isn't just meaningful for the patient; it's empowering for the patient's physician as well. It allows for enhanced flexibility in terms of deciding what treatments and interventions are most appropriate to keep the patient on a healthy track. For example, if a patient in a traditionally high-risk category has a zero CAC score, you can have a nuanced discussion about taking a daily statin pill — based on lifestyle, interest, familial history, etc. — rather than just prescribing it. A similar reasoning applies to other interventions, with the added consideration of potentially large out-of-pocket costs.
Novel medications such as GLP1 receptor agonists for patients with diabetes or PSK9 inhibitors for patients with severe hypercholesterolemia can cost thousands per year, even with insurance. If the patient has an exceedingly high CAC, the absolute reduction of risk can be dramatic with these interventions. But, if the patient has zero CAC, the reduction in absolute risk will be more modest.
According to Nasir and Cainzos-Achirica, “In a context of progressively low estimated ASCVD risk thresholds for consideration of preventive therapy with statins in international primary prevention guidelines, CAC=0, which is associated with low event rates in several populations, has become a particularly powerful prognostic tool and may be incorporated in clinician-patient discussions to guide the safe avoidance of preventive therapy with statins and aspirin. Moving forward, ongoing studies will help define the potential role of CAC informing the personalized allocation of other risk reduction therapies among several populations, such as individuals with diabetes and severe hypercholesterolemia.”
Studies conducted by Nasir, among others, suggest that patients are more compliant when they have an accurate picture of their burden of plaque. It improves adherence to both lifestyle changes and medication to know how much is riding on these interventions.
Khurram Nasir, Miguel Cainzos-Achirica. Role of coronary artery calcium score in the primary prevention of cardiovascular disease. BMJ. 2021 May 4;373:n776. doi: 10.1136/bmj.n776.
Abanti Chattopadhyay, PhD, May 2022
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