Written by Leonidas Miras, MD, and Lev Lubarsky, DO, FSCCT
Early stages of coronary artery disease (CAD) don’t usually start with symptoms. In fact, plaque can build up in your arteries for years before you ever feel chest pain or shortness of breath. That’s why early detection is so important and why CT cardiac imaging has become such a powerful tool in prevention over the past 20 years. Two tests you may hear about are the coronary calcium score and the coronary CT angiogram (CTA). Although they sound similar, they serve different purposes. Understanding the difference can help your doctor choose the right test at the right time.
The Coronary Artery Calcium Score (CAC): A Window Into Your Future Risk
A calcium score is a quick (less than five minutes and very low X-ray radiation) CT scan that looks for calcified plaque in your coronary arteries. Over time, cholesterol buildup in the arteries can harden and form calcium deposits. This test measures how much of that calcium is present. The result is given as a number, which correlates with your risk of heart disease:
- A score of 0 suggests very low risk.
- Higher scores indicate increasing density and size of the blockage and signify a higher risk for adverse cardiac events over the next 5 to 10 years.
- The CAC score also allows for comparison of your result against people of the same age, ethnicity, and gender (so-called MESA percentile).
What makes this test especially useful is that it helps guide preventive care. For example, if your calcium score is elevated, it should encourage you and your doctor to be more aggressive with cholesterol management, lifestyle changes or possibly medications.
However, the calcium score has an important limitation: It only detects long-standing cholesterol blockages, which already had time to incorporate at least some calcium. It does not show earlier stages of plaque. As such, doing CAC in patients under 45 is not advisable, as a CAC score of zero may not be as predictive of low cardiac risk as it is in people over 45.
Coronary CT Angiogram (CTA)
A coronary CTA is a more advanced CT scan that uses IV contrast to visualize the whole heart and its vessels, inside and out (versus just the silhouette of the vessel and presence of calcium, as is done by CAC scoring). Unlike the CAC score, this test can detect:
- Both calcified and a more recently developed non-calcified plaque.
- The actual degree of narrowing (blockage) in the arteries (so-called percent stenosis).
- The overall structure and anatomy of the heart and the coronary arteries.
This makes CTA incredibly valuable for patients who are experiencing symptoms such as chest pain. It allows us to determine whether there is a significant blockage that might require further treatment and, therefore, in some cases, may replace doing a stress test. CTA is often described as having a very high negative predictive value. Meaning, if the CTA is normal, we can be very confident there is no significant coronary artery disease; it’s been shown to have a “no heart attack warranty” for over two years.
The CTA test does require intravenous contrast, involves slightly more radiation, and may not be suitable for patients with kidney issues, irregular or overly fast heart rate, and very senior patients.
The key difference between CAC score and CTA is, which question are we trying to answer by the result of the test?
- The calcium score helps us understand your cardiac risk over the next decade.
- The coronary CTA helps us determine if your symptoms are secondary to coronary artery disease. In addition, CTA provides an in-depth analysis of all coronary arteries by detecting any composition of blockages. All coronary CTA examinations also include CAC scores.
Which Test Should You Get?
The answer depends on your symptoms and your overall risk profile. If you feel well and are simply trying to understand your heart health, a calcium score is often the best place to start. It gives us valuable information that can guide long-term prevention.
If you are experiencing symptoms, especially chest pain or unexplained shortness of breath with activities, a coronary CTA is a better test. Your doctor will take into account your age, medical risk factors, and clinical picture before recommending the most appropriate test.
The Bottom Line
Both tests are valuable, but they are used in different ways. At North Suffolk Cardiology, our doctors have been using CT technology for more than 15 years, and some have been leaders in advanced cardiac imaging within the medical community. We can provide our expertise in choosing the right test, arranging it and interpreting the actual CT images. CAC and CTA imaging can help answer many common questions, such as: “Do I need to take aspirin?”; “Do I need cholesterol-lowering medication, such as a statin?” and “What are my chances for having a heart attack over the next few years?”
To schedule an appointment with North Suffolk Cardiology, call (631) 941-2000.