In my cardiology practice, I encounter a fair number of young to middle-age patients who are interested in screening for cardiovascular disease. For some, it’s just curiosity, while others are eager to explore their own health due to having a strong family history of heart attacks or strokes, or because they themselves have had one or more cardiac risk factors (smoking, diabetes, high cholesterol, high blood pressure).
One test that often comes up is a coronary artery calcium score. This test uses a CT scanner to detect calcium in the walls of the coronary arteries. There is a standardized scoring system (agatston score) which is calculated based on the extent and density of the calcium. The test is usually not covered by insurance, but is typically available at a cost of less than $100. It usually takes about 10-15 minutes to perform, and exposes a patient to a low dose of radiation (similar to that of a mammogram).
Calcified cholesterol plaques develop in the arterial walls due to a complex interplay of cholesterol in the blood, inflammation, hormones, and metabolic factors. The identification of cholesterol plaques is indicative of a chronic process, meaning that the plaques seen on a coronary calcium study have been developing over many years.
The coronary calcium score gives no information on whether or not there is narrowing of a particular vessel, only on the presence and extent. It does allow us to separate patients into different risk categories, and to refine cardiovascular prognosis. If the score is elevated (typically >400 or 75th percentile for age and gender), we may consider performing a stress test in order to determine if there is any physiologic significance to the plaque buildup (by not allowing enough blood to reach the heart muscle).
Calcified plaques tend to be more stable than less mature soft plaques, meaning they are less likely to rupture and result in an abrupt heart attack. They can, however, cause progressive narrowing of a blood vessel to the point where blood flow to the heart muscle is compromised and a patient experiences chest pain (angina).
So when is the best time to utilize a coronary calcium study? In patients we deem to be at intermediate risk for cardiovascular events over the subsequent decade.
Typically, when deciding a patient’s risk for cardiovascular events, we take into account traditional risk factors and also use something called the Pooled Cohort Risk Assessment Equation. This is a tool which estimates a patient’s future risk of cardiovascular events using information such as age, cholesterol numbers, and the presence or absence of high blood pressure, tobacco use, and diabetes. It was developed by following outcomes in various populations over time.
While the equation is good at estimating general risk based on population data, it is imperfect at predicting individual risk due to variances in genetics and lifestyle. Typically, the tool is utilized in patients aged 40-79 years old. The calculator will place patients into one of several risk categories including low (<7.5%), intermediate (7.5%-20%), or high (>20%).
It is in the middle category (intermediate) where use of calcium scoring is most beneficial to refine risk, and to help make clinical decisions regarding use of cholesterol medications and aspirin. Additionally, the presence of coronary calcium can be a wonderful motivating factor to initiate lifestyle changes such as dietary modification and exercise.
While many patients younger than 40 will have some plaque buildup, usually this is too immature to become calcified. Current guidelines do not recommend using calcium scoring as a tool in this population (men younger than 40 and women younger than 50). It is also not recommended in those deemed to be at high risk (>20%) or low risk (<7.5%) by the Pooled Cohort Equation, or those with known coronary artery disease (especially if they have had a previous heart attack, stents, or bypass surgery). Scoring is unlikely to influence treatment decisions in any of these populations.
It is currently not recommended to do serial testing as many soft plaques may become calcified (more stable) with lifestyle changes and cholesterol medications. There is some preliminary data that changes or stability in calcium level over 5 years might have some prognostic value, however this strategy is currently not mainstream.