A Computed Tomography (CT) scan uses X-rays and computer processing to create detailed, cross-sectional images of the body’s internal structures. By taking multiple images from various angles, the technology constructs high-resolution, three-dimensional views of organs and tissues. Specialized protocols have been developed to capture the rapid motion of the heart. These cardiac CT scans provide specific anatomical information, allowing visualization of the heart muscle, its chambers, and major blood vessels.
Different Types of Cardiac CT Scans
Cardiac CT scans primarily evaluate heart health using two methods: Coronary Artery Calcium (CAC) Scoring and Coronary CT Angiography (CCTA). CAC scoring is a quick, non-contrast scan that measures the amount of calcified plaque within the coronary arteries. This measurement results in the Agatston score, which predicts future cardiovascular risk.
CCTA is a more detailed examination requiring an intravenous injection of iodine-based contrast dye. The contrast highlights the coronary arteries, allowing direct visualization of the vessel walls. CCTA assesses the degree of narrowing (stenosis) and characterizes the type of plaque, including both calcified and non-calcified material. For both scans, the CT machine synchronizes with the heart’s electrical activity to minimize motion blur and capture clear images.
Identifying Coronary Artery Disease
Cardiac CT scans are effective for diagnosing Coronary Artery Disease (CAD), caused by plaque buildup in the heart’s arteries. A CAC score of zero indicates no detectable calcified plaque, suggesting a low risk of a heart attack in the short term. A score of 101 to 400 suggests a moderate amount of plaque and a moderate to high chance of future cardiac events, prompting changes in treatment plans.
The CCTA provides an anatomical map of the coronary arteries, quantifying plaque burden and the degree of stenosis. It identifies non-calcified plaque, which is often rich in lipids and considered vulnerable to rupture, an event that can trigger a heart attack. Identifying the location and severity of narrowing helps determine if a blockage restricts blood flow, guiding decisions on whether a patient requires intervention or aggressive medical therapy.
Visualization of Heart Structure and Aorta
Beyond the coronary arteries, the cardiac CT scan provides comprehensive imaging of the entire heart and the great vessels. This allows for the assessment of the pericardium, identifying conditions such as inflammation or excessive fluid collection. The scan is valuable for evaluating the aorta, the body’s largest artery, to detect life-threatening conditions like aneurysms or aortic dissection (a tear in the wall’s inner layer).
The detailed 3D reconstruction capabilities of the CT scan play a significant role in planning complex structural heart procedures. It is frequently used to precisely measure the heart’s chambers and major valves, which is essential for pre-procedural planning of interventions like Transcatheter Aortic Valve Replacement (TAVR). CT can also visualize congenital heart defects in adults, such as abnormal connections between chambers or vessels, providing anatomical detail that other imaging modalities may miss.
What Cardiac CT Scans Cannot Determine
While cardiac CT scans excel at showing heart anatomy, they have limitations in assessing the organ’s function. The scans do not measure the heart muscle’s pumping ability, known as the ejection fraction, which measures heart failure. CT scans also cannot detect irregularities in the heart’s electrical system, meaning they are not used for diagnosing arrhythmias or electrical conduction issues.
The technology does not always determine the functional impact of an observed blockage. Although CCTA identifies narrowing in an artery, it does not directly show whether that stenosis limits blood flow to the heart muscle (ischemia). For a full assessment of blood flow dynamics and muscle function, a CT scan is often used with other diagnostic tools, such as an echocardiogram or a stress test.