For decades, many investigators have been trying to find the “factors” that increase the risk of Myocardial Infarction (MI). Through many years of intensive and elegant research, they have successfully identified many risk factors, known as “traditional risk factors.” . These include Smoking, Obesity, and sedentary lifestyle, hypercholesterolemia, hypertension, positive family history of myocardial infarction, inflammatory diseases like rheumatoid arthritis, and last but not least, diabetes. Extensive research has proven that we can reduce the risk of MI by modifying these factors significantly.
Nevertheless, despite these massive efforts and findings, we see many young individuals who suffer from myocardial infarction without any “traditional” risk factors. This fact suggests that our current risk calculators, which we developed based on “traditional risk factors,” are not perfect. They have the potential to miss many cases of “preventable” acute coronary syndromes.
During the past 15 years, coronary calcium score has emerged as a reliable tool to add to the already known mix of the risk factors to assess someone’s future risk of acute coronary syndromes by identifying atherosclerosis.
Atherosclerosis, an inflammatory process in the arterial wall, starts at young ages and results in the formation of “plaques” in the arterial wall. As we age, the process of calcification begins in these plaques. We can identify the calcium in x-ray images, which confirms the underlying plaque in the arterial wall. These “plaques” are the main precursors of myocardial infarction.
Image: This CT scan, which belongs to a 60-year-old asymptomatic man, shows significant calcification of the LAD and RCA arteries. It implies that under this bulk of calcium, the process of “atherosclerosis” is progressing fast, which, if not controlled, can result in acute coronary syndrome. He was initially labeled as “low-risk” by his previous care provider based on traditional risk factor calculations. But this mere new fact (high coronary calcium score) will change his previous “low risk” status to “high-risk.”
How Coronary Artery Calcium is measured and how much it costs?
Who needs a Coronary Artery Calcium score check and when should you consider it?
There has been significant debate as to when and in what clinical situation a coronary calcium score should be considered. CAC Score is a preventive tool and should not be used in symptomatic patients. It is another piece of the puzzle to shed more light on someone’s future risk of Acute Coronary Events.
To illustrate how the CAC score check can be helpful, here I present a typical case.
CASE: A 55-year-old man presents to you after his close friend suffered a massive myocardial infarction. They have been colleagues and used to exercise regularly with weekly swimming, cycling, and running regularly and intensely. He does not smoke, eats healthy, and does not have any significant family history of ischaemic heart disease. His cholesterol is on the low side, and has mild hypertension, which is well controlled with a low-dose antihypertensive. He is not complaining of any symptoms indicative of angina. He insists that his friend had the same profile and was at low risk for myocardial infarction. In this scenario, a test that can add significant weight and information to stratify his risk for future IHD is a coronary calcium score. He performs a CAC score, which comes back as 300. A calcium score at this level will move him from low-risk category to moderate to a high-risk category immediately. He will undoubtedly benefit from intensive reduction of his LDL to 1.4-1.6 mmol/L and the addition of Aspirin.
This case clearly illustrates that coronary artery calcium score should be considered in the “low-risk” patients. High-risk patients should be on intensive therapy with Statins and Aspirin, and CAC score does not alter the management.
What is the ideal age to consider coronary artery calcium scoring?
Calcium score should be considered in people between 45-70 years of age. This does not imply people below 40 or above 70 cannot have the test, but the interpretation should be guarded outside this range. Under 40, the zero score’s negative predictive value is not high since there has not been enough time for the lipid-rich-plaques to calcify. This core may be misleading. On the other hand, a high calcium score has a very high positive predictive value at a young age. It shows that they already have coronary plaques and are at a very high risk of future IHD.
Above the age of 70, nearly everyone has calcification of the coronary arteries. Having a positive score in the elderly, unless significantly elevated, does not necessarily signify high risk. On the other hand, a calcium score of 0 in this age group has a very high negative predictive value.
How should we interpret a calcium score of 0?
Coronary artery calcium score should always be interpreted along with the other risk factors and never solely. A calcium score of 0 in a low-risk patient at the right age group has a very high negative predictive value for future IHD, up to 95% in the next 2-5 years. The same calcium score in someone who smokes and has high cholesterol certainly has a lower negative predictive value and should be interpreted carefully. Other risk factors should always be treated and dealt with diligently, even if the coronary calcium score is 0. Patients should always be advised against smoking, treated for hypercholesterolemia and hypertension, and be encouraged to perform regular exercise and eat healthy, even in the presence of a calcium score of 0.
Should the calcium score be ever repeated?
If a calcium score is positive, it should not be repeated ever. The patient needs to be treated aggressively, along with lifestyle modifications. There has been some suggestion that if the calcium score is 0, it may be repeated after 5 years “to see the change.” But in my opinion, if the test was done in a low-risk patient from the right age group, we do not need to repeat the test.
On the other hand, if the zero CAC score was in a 40-year-old patient with pre-diabetes and some other minor risk factors, maybe in 5-10 years, he could have a repeat check. This only applies if he is still in the low to the intermediate-risk group. If he has already moved to the high-risk group, he needs aggressive treatment instead of a calcium score check.
Important message to remember:
In an asymptomatic but high-risk patient (someone with a strong family history of IHD, sedentary lifestyle, and hypercholesterolemia), do not let a low calcium score (even if zero) deter you from intensive medical therapy and further cardiac assessments like stress test. In this scenario, the low (or zero) calcium score has a low negative predictive value. It should not be done as the first-line test for risk assessment.
How should a high calcium score be interpreted?
Coronary artery calcium score should be interpreted according to age. A calcium score of 20 in a 70-year-old person is low but is significantly elevated for 35-40-year-old. Usually, any calcium score above 300-400 should be considered considerably elevated. Intensive medical therapy and risk factor modifications are strongly recommended.
If someone is already on statin therapy, should we bother checking their coronary artery calcium score?
If they have an LDL close to 1.5 mmol/L and are on aspirin, there is no need to check the calcium score. But suppose the LDL is not on target (let’s say above 2 mmol/L). In that case, a very high coronary artery calcium score signifies that statin therapy needs to be intensified. I also find it a potent motivating factor for the patient to change their lifestyle.
- deGoma EM, Knowles JW, Angeli F, Budoff MJ, Rader DJ. The evolution and refinement of traditional risk factors for cardiovascular disease. Cardiol Rev. 2012;20(3):118-129. doi:10.1097/CRD.0b013e318239b924