Coronary Calcium Score coronary calcification

Coronary Calcium Score (Coronary Artery Calcification): Nuts and Bolts

Backgorund:

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.” [1]. 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. Research has proven we can significantly reduce the risk of MI by modifying these factors.

Despite these massive efforts and findings, still some young individuals suffer from myocardial infarction without any “traditional” risk factors. This fact suggests that our current risk calculators, which were 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.

Click to enlarge

Figure 1: 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 syndromes (heart attack). He was initially labeled as “low-risk” 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?

When should consider Coronary Artery Calcium check? 

There has been significant debate as 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 (if someone has chest pain or shortness on breath). It is another piece of the puzzle to shed more light on someone’s “future risk of a Heart Attack”. 

Before considering a calcium score, it is crucial to calculate the patient’s baseline risk of a heart attack. This can be done by many online calculators like this online calculator from the American College of Cardiology. It needs a few baseline information like the presence of Diabetes, Hypertension or high cholesterol levels. Smoking status, age and medications are other components. Based on this information, a 10-year risk estimate is generated. The patient will be categorised either as low-risk, intermediate-risk, and high-risk for future heart attacks. 

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 only be considered in “low to intermediate-risk” patients.  A high coronary calcium score can change someone’s risk from low to high but not the other way. A low or even zero calcium score does not change the status of a high-risk patient to a low-risk. A “high risk” individual will remain “high risk” regardless of their calcium score. High-risk patients should be on intensive therapy with Statins and Aspirin, and encouraged to change their lifestyle.

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 mean that 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 in the context of other risk factors and never solely. A calcium score of 0 in a low-risk patient is highly reassuring. However, the same score in someone who smokes and has high cholesterol or blood pressure is much less predictive. Other risk factors should always be treated and dealt with diligently, regardless the coronary calcium score. Patients should always be advised against smoking, treated for hypercholesterolemia, hypertension, diabetes and be encouraged to perform regular exercise and eat healthy, even with a calcium score of 0.

Figure 2: This example shows a significant narrowing in a coronary artery while there is no calcium. This person has been a “high risk” patient with a calcium score of zero! If no further assessment had been done, he would have had a significant heart attack. This example illustrates why Coronary Calcium Score is not a test for “high-risk” patients. 

In high-risk patients, a low or zero calcium score can provoke leniency toward treatment goals by doctors and non-adherence to medical therapy by patients with detrimental consequences.

Calcium-score-zero-and-severe-coronary-stenosis
J Am Coll Cardiol. 2008 Jul, 52 (3) 216–222 -- Click to enlarge

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.

Should the calcium score be ever repeated?

If the calcium was elevated, it should not be repeated ever. The patient is at high risk, and they need intensive treatment for their risk factors and lifestyle modifications. There is also mounting evidence that statins and Aspirin would reduce the risk of heart attack significantly in this scenario.

If the calcium score was 0, in the lower tier of the age group, the test might be repeated after 5 years “to look for a significant rise”. This is especially more sensible if they have a few risk factors like high cholesterol or blood pressure.

If someone is already on statin therapy, should we bother checking their coronary artery calcium score?

If they take Aspirin and statin with an LDL close to 1.5 mmol/L, there is no need to check the calcium score. But suppose the LDL is not on target (let’s say above 2 mmol/L), and they have a very high coronary artery calcium score. This suggests that their cholesterol management needs to be intensified. I also find it a potent motivating factor for patients to change their lifestyles and adhere to medical treatment.

In the following video, I present a real case and show how Coronary Calcium Score can change someone’s cardiovascular risk profile, how it can be helpful or harmful in different scenarios.

How to interpret Coronary Calcium Score, explained with a case:

The coronary artery calcium score is only another puzzle piece to add to the overall risk factors mix. Like any other test in medicine, it has pros and cons, can be helpful or harmful and should be used judiciously. It clarifies someone's risk for future ischaemic heart disease and should never be interpreted solely without having the whole picture in mind.

Coronary Artery Risk Factors

References:

  1. 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. 
  2. Maureen M et al. Noninvasive Evaluation With Multislice Computed Tomography in Suspected Acute Coronary Syndrome: Plaque Morphology on Multislice Computed Tomography Versus Coronary Calcium Score. J Am Coll Cardiol. 2008 Jul, 52 (3) 216–222
Dr Reza Moazzeni MD, FRACP

Dr Reza Moazzeni MD, FRACP

Dr Moazzeni is a Consultant Cardiologist practising at Westmead and St Leonards in Sydney, NSW. He has a special interest in cardiac imaging, including Echocardiogram, Stress Echocardiogram, CT coronary angiogram, coronary artery calcium score, and preventive medicine.

Heartcare Sydney

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My score went from a zero to 32 in a span of 4 years. as a 60 year old male, should I be concerned?

very informative. Thanks

Thank you. Very informative!

This discussion and particularly the video was excellent. I have a family history of heart disease. Starting with my primary physician and the through screening programs offered by a local hospital I’ve had regular vascular, CT scans and calcium scores.

The results were interpreted for me by my primary physician, but frankly I never really understood what she was telling me. Your video was extremely helpful in understanding how plaque develops.

Have you made, or do you know of other videos related not the issues that I should understand related to “intervention” options that – base on my family history – will likely be needed at some point?

Great review of the subject and video, thank you

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