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Understanding Coronary Artery Calcium

M3 India Newsdesk May 06, 2024

Coronary Artery Calcium (CAC), a marker of atherosclerosis, is pivotal in assessing cardiovascular risk. This article underscores its importance in risk stratification, personalised therapy initiation, and shaping preventive strategies for a healthier future.

Coronary Artery Disease (CAD) is a manifestation of coronary atherosclerosis and symptomatic manifestations of CAD vary from sudden cardiac death, to acute along with chronic coronary syndromes and heart failure.

In certain individuals, the process is relentlessly aggressive and accelerated clinical manifestations may lead to premature death. It is also known that almost 50% of all cardiovascular disease-related deaths happen in patients with no prior symptoms or diagnosis.

CAD is the single most important cause of mortality and morbidity across the globe irrespective of gender, social and economic status.

It is thus quite natural that for years researchers have been trying to understand the mechanism of evolvement of disease and predict those who are at high risk for accelerated disease progression.

Risk stratification would enable close monitoring and application of disease-modifying therapies for those at enhanced cardiovascular risk. A patient with a non-obstructive vulnerable plaque with luminal patency for blood flow in coronary arteries may have a normal stress test. This greatly limits the utility of the stress test decreasing its positive predictive value. There are few other patients who are unable to exercise such as those with osteoarthritis and where risk stratification is even more needed.

Coronary Artery Calcium (CAC) is an established non-invasive tool for assessing risk stratification and overall atherosclerotic plaque burden in the asymptomatic primary prevention population. In fact, it is the most robust risk calculator for intermediate-risk populations with more accuracy than other predictors such as estimation of high-sensitivity C-reactive protein and ultrasound testing for carotid-intima media thickness.

CAC is detected by using computed tomography and is quantified with the help of the Agatston method (Table 1). It does not involve high radiation doses as coronary CT angiography and avoids injection of contrast media. The approximate radiation dose for a single test is 1 mSv. Thus, the fact that it is accomplished quickly without exercise effort by the patient is a major advantage.

CAC score Risk
0 A zero score confers a very low risk
1-99 Low risk
100-399 Intermediate risk
101-399 and >75th centile Moderately high risk
≥ 400 High risk

Table 1: The risk category of myocardial infarction and coronary mortality at 10 years by coronary artery calcium score 

The greatest utility of CAC is in patients who are in low-risk or intermediate-risk categories. We must remember that those who are at elevated high risk would not be impacted even if CCS is low or zero. The utility of CAC helps us identify high-risk individuals in intermediate-risk populations so that aggressive pharmacotherapy early if needed could be applied to them.

A low or even zero CAC should always be interpreted in high-risk individuals in the presence of other comorbidities. It must be kept in mind that a zero score would not rule out obstructive CAD if the patient is at otherwise high risk due to the presence of multiple risk factors. CAC remains a viable tool for patients with intermediate pre-test probability. This fact has been highlighted by a study published in the journal by et. al. Thus, it is not worthwhile to perform the test in those with established CAD or those with highly symptomatic status with multiple comorbidities.

CAC progression may happen over each passing decade and it also depends on risk factors present in the patient and the lifestyle the patient pursues.

It is important to understand the risk stratification with the help of CAC, as that would enable a personalised approach for the initiation of therapies such as aspirin, statins and aggressive risk factor management in high-risk individuals. This also helps in forming decisions regarding the rescanning of CAC time intervals.

Keeping in mind the current guidelines and thus summarising the ideal patient who would benefit from CAC would be more than 40 years of age, with an intermediate-risk profile and who is mostly asymptomatic.

How best can we decide on treatment based on CAC?

A score of more than 100 is an indication to start statins. On the other hand, if the score is 0, we may downgrade the risk and reassess the scan after 5 years. This observation is based on MESA (Multi-Ethnic Study of Atherosclerosis ) in which it was observed for 10 years MACE were 1.3%-5.6% for CAC = 0, and from 13.1%-26.6% for CAC >300. When considering other cardiovascular risk factors to be constant, the MESA study found that for each doubling of coronary Artery Calcium (CAC) levels, there was an estimated 14% increase in relative risk.

Perhaps the greatest utility of CAC is in its being non-invasive, quick and without the need for exercise, which is quite a limiting factor for many patients such as those with osteoarthritis. It also helps in patients with kidney disease where contrast conservation is an important prerequisite.

It helps in risk stratification much more than other parameters such as HsCRP and carotid-intima media estimation. CAC also helps in giving the right patient the best current prevention medication such as aspirin and statins.


Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author, Dr. Arun Kochar, is
 an additional director of cardiology at Fortis Hospital, Mohali.

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