Coronary Computed Tomography Angiography (CCTA) is a non-invasive medical imaging examination that provides detailed, three-dimensional pictures of the coronary arteries, which supply blood to the heart muscle. This test uses a specialized computed tomography (CT) scanner and an intravenous contrast dye to visualize the blood vessels. The purpose of CCTA is to detect potential abnormalities in blood flow and is a common tool for evaluating patients experiencing symptoms of heart disease.
The Purpose and Function of CCTA
A physician will typically order a CCTA to detect and assess the presence of Coronary Artery Disease (CAD), which involves the buildup of plaque in the coronary arteries. The primary function of the test is to clearly identify any narrowing, or stenosis, within these vessels, often caused by fatty deposits composed of calcium, cholesterol, and fat. CCTA is highly effective at visualizing both hard, calcified plaque and softer, non-calcified plaque, providing a comprehensive view of the artery walls. The test helps determine if chest discomfort or shortness of breath is a result of reduced blood flow due to blocked arteries. CCTA also offers a tool for risk stratification, especially when combined with a non-contrast Coronary Artery Calcium (CAC) score. While the CAC score measures only hardened plaque, the full CCTA scan with contrast can visualize the entire extent of the disease, guiding decisions about the need for further, invasive procedures like traditional angiography.
Preparing for the Scan
Proper patient preparation is important for obtaining clear, diagnostic images, as the heart is a constantly moving organ. Patients are typically instructed to fast from food for about four hours before the test, though they are encouraged to drink plenty of water for hydration. This fasting helps minimize potential nausea from the contrast dye and ensures a smoother procedure.
A major preparatory step involves controlling the heart rate, as a slower, more regular beat provides a sharper image. Patients are advised to avoid all sources of caffeine, as well as nicotine, for 12 hours prior to the scan, as these can elevate the heart rate. To achieve an optimal heart rate, often targeted at 60 to 65 beats per minute or less, a patient may be given a beta-blocker medication, either orally or intravenously, before the scan begins.
The CCTA Procedure
Upon arrival for the CCTA, a nurse or technologist will insert an intravenous (IV) line, usually in the arm or hand, to administer the contrast material later in the procedure. Small, sticky patches called electrodes are placed on the chest and connected to an electrocardiogram (EKG) machine to continuously monitor the heart’s electrical activity and rhythm. This EKG monitoring allows the CT scanner to precisely time the X-ray acquisition to the brief moment when the heart is between beats, minimizing motion blur.
The patient lies on the CT scanner table, which slides into the large, open, doughnut-shaped machine. Just before the images are acquired, an iodine-based contrast dye is rapidly injected through the IV line. This contrast material travels through the bloodstream, temporarily making the coronary arteries highly visible on the CT images. Patients commonly feel a warm, flushing sensation and may experience a metallic taste in their mouth as the dye circulates, which are expected side effects. The technologist will instruct the patient to hold their breath for a brief period, typically 10 to 15 seconds, while the scanner quickly captures the necessary images.
Understanding the Results
A physician, often a cardiologist or radiologist, interprets the CCTA images to create a comprehensive report. The images reveal the location, extent, and severity of any plaque buildup or blockages within the coronary arteries. The results are often classified using a standardized system that describes the degree of narrowing, ranging from normal arteries with no disease to significant stenosis.
The findings guide the patient’s next steps in care; for example, a normal result may allow the physician to rule out CAD as the cause of symptoms and explore other possibilities. Results showing non-obstructive CAD, which is a mild plaque burden without significant narrowing, generally lead to recommendations for lifestyle changes and medication to reduce future risk. Conversely, the identification of a severe blockage often prompts a discussion about more intensive treatments, such as further testing or interventional procedures to restore blood flow.