Introduction
Video: This video illustrates the main differences between the CT Coronary Angiogram and CT Calcium Scoring and when each test is indicated.
The heart has been the primary focus of intensive research over the past century, leading to significant advancements in cardiology and cardiac imaging techniques. The CT Coronary Angiogram (CTCA) and the CT Coronary Artery Calcium Score (CAC Score) are commonly used non-invasive diagnostic tools for assessing cardiac health. While the CTCA serves primarily as a diagnostic test, the CT calcium score is a “risk assessment” tool without diagnostic implications. Understanding the distinctions between these two imaging techniques is essential for patient management, as overlooking their differences can lead to severe, life-threatening consequences. In this article, I delineate the differences, limitations, and indications of these imaging techniques.
CT Coronary Angiogram (CTCA)
A CT Coronary Angiogram is a specialized computed tomography (CT) scan that captures detailed images of the coronary arteries. It uses intravenous contrast dye to highlight blood vessels, allowing physicians to evaluate blood flow and identify any narrowing or blockages due to plaque build-up.
Indications for CTCA:
- Suspicion of coronary artery disease (CAD) in patients with chest pain or other symptoms suggestive of angina.
- Evaluation of patients with abnormal stress echocardiogram results.
- Assessment of coronary artery bypass grafts (CABG) or stents.
- Preoperative evaluation before non-cardiac surgery for patients with known CAD or multiple risk factors.
Limitations of CTCA:
- Exposure to ionizing radiation and iodinated contrast dye, which may cause allergic reactions or kidney damage in some patients.
- Inability to accurately evaluate calcified plaques, as they can cause blooming artifacts that may obscure the lumen.
- Inability to measure the physiological significance of stenosis (i.e., whether the stenosis has compromised blood flow).
- Not recommended for patients with known allergy to iodinated contrast dye, severely impaired kidney function, or pregnant women.
CT Coronary Artery Calcium Score (CAC Score)
The coronary artery calcium score measures the amount of calcified plaque in the coronary arteries. It uses a non-contrast CT scan to quantify calcium deposits, which are then used to calculate a score. A higher score indicates a higher risk of future cardiac events.
Indications for CAC Score:
- Asymptomatic patients with low to intermediate risk for CAD to help redefine risk stratification and guide preventive strategies.
- Patients with a family history of premature CAD.
- Evaluate patients with atypical chest pain after a normal functional test like a stress echocardiogram or myocardial perfusion scan.
Limitations of CAC Score:
- Exposure to ionizing radiation, albeit at a lower dose compared to CTCA.
- Inability to detect non-calcified plaque, which can still cause significant stenosis and contribute to CAD.
- No information about the severity of luminal narrowing or blood flow impairment.
Conclusion
The CT Coronary Angiogram and CT Calcium Score are valuable diagnostic tools for assessing cardiac health. CTCA is typically used for individuals experiencing symptoms such as chest pain or when abnormalities are detected during a stress echocardiogram. Although CTCA offers a detailed evaluation of coronary arteries, it involves higher radiation exposure and the use of contrast dye.
In contrast, CAC Score quantifies calcified plaque burden. It aids in risk stratification but lacks information about non-calcified plaque or blood flow impairment. CAC Score is recommended for individuals without symptoms or those with a normal stress echocardiogram to assess future heart attack risk and guide therapy. It’s essential to note that CAC Score should not be used for high-risk individuals, such as those with multiple risk factors for CAD, or Familial Hypercholesterolemia (FH), as it may not detect non-calcified plaques and blockages. This crucial point about CAC Score is further explained in this post, along with a real case study for better understanding.
Physicians should consider the indications and limitations of each technique before recommending them to patients, ensuring the most appropriate test is utilized for each individual's cardiac care. By understanding the roles and limitations of CT Coronary Angiogram and CT Calcium Score in a heart health evaluation, patients and healthcare providers can make informed decisions that best suit the needs of each unique situation. As we continue to focus on heart health in the 21st century, optimizing the use of these diagnostic tools will remain crucial for the early detection and prevention of coronary artery disease.
I had a CT calcium score of 0 4 years ago. Because I had a higher than usual cholesterol recently 281 my doctor repeated the CT calcium score test. This time it was 6. Does that slight change justify starting on statin therapy.
Thank you for your question.
A change in your CT calcium score can seem concerning, but it’s important to interpret this result within a broader clinical context. Decisions about starting statin therapy—or any medical treatment—should not be based solely on the coronary calcium score. While the CAC score can provide insight into coronary calcification, it is one piece of a much larger puzzle.
The value of a CAC score lies in its integration with other risk factors, including cholesterol levels, blood pressure, smoking status, family history of heart disease, age, and other lifestyle considerations. The best approach is to discuss these risk factors comprehensively with your healthcare provider to determine whether statin therapy is appropriate for you based on your overall risk profile, not just a single test result.
A few months ago, my father had a calcium CT scan, his score was 1420. He has since seen a cardiologist and they have significantly increased his dose of cholesterol medication and requested a stress test in 5 weeks time. My question is, with his score being so significantly high, why hasn’t he requested an urgent angiogram and possible stents? Or will this come after the stress test?
Hi Laura,
The Coronary Calcium Score (CAC score) is primarily a “risk-assessment” tool. It’s used to gauge a person’s risk of future heart events, especially for those initially categorized as low-risk based on traditional evaluations. A high CAC score, like your father’s, reclassifies a person into the high-risk category, necessitating more aggressive medical management, including aggressive cholesterol reduction. It also serves as a powerful motivator for adopting a healthier lifestyle.
However, the CAC score should not be used to dictate invasive procedures like angiograms directly. The decision for such procedures is largely driven by the patient’s symptoms and clinical presentation. Your father’s cardiologist is adopting a systematic approach that aligns with best practices. I encourage you to trust and follow their guidance.
I thought the CT coronary angiogram would also be able to tell you if you had soft plaque as well as calcified plaque and distinguish between the two. I just had a CT coronary angiogram with contrast and it did not distinguish between the 2 types and the was the purpose of obtaining the test. Why is that?
CT Coronary Angiogram (CTCA) uses intravenous contrast to highlight areas of blockage, and it can, indeed, visualise both calcified and soft (non-calcified) plaques. However, while detecting calcified plaques is straightforward, detecting soft plaques can be challenging. Modern CT scanners offer impressive resolution but might sometimes miss small or diffuse soft plaques, especially if the plaque is not associated with an area of stenosis or arterial narrowing. The interpretation can also vary based on the radiologist’s or cardiologist’s expertise.
I was scheduled for a nuclear stress test I have had a cardiac arrest 3 years ago and a defibrillator and stents were put in. I have been symptom free the entire time. To my knowledge I was never given a CCS or CTCA. Would it be useful to have these? and if so, should it be fore or after the NST
Hi, Given your history of cardiac arrest and prior angioplasty, a coronary calcium score is not relevant to your care and is not recommended. CAC score is typically ordered for certain “low-risk” individuals to verify their risk status. You’re considered high-risk, necessitating intensive medical therapy and lifestyle changes. Whether to opt for a Nuclear Stress Test or CT Coronary Angiogram depends on your specific circumstances, symptoms and indications for testing. Your cardiologist, who knows your full medical history, would be in the best position to guide you in this regard.
Thank you. Great explanation. I had score of 215 and was wondering why my doctor did not order the angiogram. I understand it better now as I have no symptoms, Your site was most beneficial in explaining the whole thing.
Thank you for taking the time to comment on the post, and I’, glad you found it helpful. The distinction between CT calcium scoring and CT coronary angiogram is crucial for patients and practitioners. For those particularly interested in reading more about the coronary calcium score, I’ve discussed this topic in detail in this post. It provides further context on how it plays a role in cardiovascular risk assessment.
excellent explanation between the difference of Coronary Calcium score and Coronary Angiogram
Thank you. Glad it was useful.