Coronary Artery Calcium Scoring

Why is this test done?

It’s a common fact that coronary artery disease is the number one killer in the United States. But did you know the majority of people experiencing their first heart attack don’t have high cholesterol?

Among many of these patients, coronary artery disease – often leading to heart attacks – develops as a result of cholesterol plaque buildup that can calcify in the coronary arteries. This calcium can be detected by a cardiac computed tomographic scan (CT scan).

Traditional clinical risk prediction tools (like Framingham risk score) that use age, gender, smoking status, cholesterol levels, etc. fail to identify a significant proportion of patients who are at high risk of experiencing a coronary event. A CT scan has proven to provide incremental prognostic power over clinical variables alone. Thus, a calcium scan can help to identify the highest risk patients and alter treatments that may positively affect their outcomes.

How is the test done?

No special preparations are needed for the test. Unlike traditional CT scans, intravenous contrast isn’t used, so an IV line isn’t required. The entire CT scan takes just a few seconds.

What are the risks?

There’s always the risk of a falsely positive calcium score caused by things such as calcification outside the coronary arteries, metal clips, etc. This can be avoided by careful quality control of the heart scan. On the flip side, an accurate calcium score only detects calcified plaque in the coronary arteries, which is a late stage in the development of atherosclerosis. Therefore, even if the calcium score is zero, there could be soft, non-calcified plaque that isn’t detected and can cause future heart attacks.

The CT scan, like many other medical tests, leads to a small amount of radiation exposure – approximately 1 – 2 milliseivers of radiation (mSv). To puts things in perspective, the annual radiation dose we receive from natural sources is around 3 mSV per year.

Some of the other radiation doses for tests commonly used in medicine are:

  • Chest X-ray: 0.02 mSV
  • Routine CT chest: 5-15 mSV
  • CT abdomen: 10-37 mSV
  • Nuclear stress test: 10 to 20 mSV

Who should get a coronary calcium score?

This test is recommended for people who are considered intermediate risk of cardiac events (10 to 20 percent risk of heart attack over the next 10 years). These are generally men over the age of 45 and women over the age of 55 with or without some cardiac risk factors. People at a younger age will also quality if they have cardiac risk factors. The American College of Cardiology endorses coronary calcium scoring with a Class IIa recommendation for screening patients at intermediate risk of coronary artery disease.

This test is not for

  • Individuals who are “low risk.” For instance, someone who is younger than 55 years of age and has no cardiac risk factors would be considered low risk (less than 10 percent risk of heart attack in the next 10 years). Although strong data shows that high calcium scores are predictive of coronary events among low-risk individuals, current guidelines don’t recommend calcium scoring for this group due to the very large number of people who’d have to be unnecessarily tested to detect a small group with significant coronary calcium.
  • Individuals who are at high risk. People who’ve already had a heart attack or are over the age of 65 and have many cardiac risk factors are already considered high risk and need to be on aggressive therapy.

How can I get this test done?

Discuss your medical history and cardiac risk factors with your primary care physician. Ask whether a coronary calcium score would help identify your risk of having a heart attack in the next 10 years, and help guide your treatment plan to reduce your risk. Your physician will need to order this test. This test is done in the Radiology Department at the hospital.

What do I do with the results?

The score from a CT scan is based on the density and extent of calcification. Studies have shown that a calcium score of 0 predicts a 0.4 percent risk of coronary artery disease per year, which is very low risk. Most studies show that the risk of cardiac events increase approximately 3.8 fold for a score of 1-100, 7 for a score of 100-300 and 9 for a score greater than 400. The Society for Heart Attack Prevention, an independent nonprofit organization suggests the following plan of action based on calcium scores:

  • 0 - Low Risk: Address risk factors as appropriate
  • 1 - 99: Moderately high risk. Aggressive risk factor modification. Consider decreasing LDL to <130 mg/dl (optional <100 mg/dl)
  • 100 - 400: High risk. Aggressive risk factor modification, Consider decreasing LDL to < 100 mg/dl (optional <70 mg/dl)
  • Greater than 400: Very high risk. Aggressive risk factor modification, Consider decreasing LDL to < 70 mg/dl. Consider cardiology referral. A stress test may be considered (ACC/AHA class IIa recommendation)

A percentile score based on age and gender may also be calculated by using this calculator. Many studies suggest that a percentile score greater than 75 percent also suggests high risk and may merit aggressive treatment that may include a statin.