A Coronary Computed Tomography Angiography (CCTA) is a non-invasive medical imaging test that uses a powerful X-ray machine, known as a CT scanner, to produce detailed, three-dimensional images of the arteries supplying blood to the heart muscle. The procedure involves injecting an iodine-based contrast dye into a vein, which travels through the bloodstream to highlight the coronary arteries. This process allows physicians to visualize the internal structure of the blood vessels without the need for an invasive catheter inserted through the groin or wrist.
Diagnostic Goals
A physician typically orders a CCTA to evaluate a patient presenting with symptoms suggestive of blockages in the heart’s arteries. The test is most frequently used to assess the cause of unexplained chest pain, particularly in individuals whose risk of Coronary Artery Disease (CAD) is categorized as low or intermediate. By visualizing the coronary tree, the scan can quickly rule out significant narrowing or blockages, which helps prevent unnecessary invasive procedures.
The CCTA is highly effective for identifying the presence and extent of atherosclerotic plaque buildup, which is composed of fat, cholesterol, and calcium deposits. The scan helps determine a patient’s risk profile and guides decisions regarding preventive medications or lifestyle modifications. The test is also used to check the patency of existing coronary artery bypass grafts or to assess whether previously placed stents remain open.
Patient Preparation Requirements
Successful CCTA imaging relies on minimizing heart motion during the scan, which necessitates a specific preparation regimen designed to slow the heart rate. Patients are typically instructed to fast from solid food for at least four hours before the test to prevent nausea and improve image quality. Drinking water is usually permitted, but beverages containing caffeine, such as coffee, tea, or soda, must be avoided for 12 to 24 hours prior to the procedure, as caffeine can elevate the heart rate.
Before the scan, a blood test is required to check kidney function by measuring creatinine levels. This step is necessary because the iodine-based contrast dye is processed and eliminated by the kidneys, and impaired function can increase the risk of complications.
If the heart rate is too high upon arrival, the patient will receive a beta-blocker medication, often administered orally or intravenously, with the goal of achieving a rate below 60 to 70 beats per minute. Patients must also communicate any known allergies to iodine or shellfish, or existing conditions like diabetes, which may require holding certain medications, such as metformin, following the contrast injection.
The Scanning Procedure
Upon arrival for the procedure, a nurse or technologist will place an intravenous (IV) line, often in the arm, for the rapid injection of the contrast dye. Sticky electrode patches, known as EKG leads, are attached to the chest to monitor the heart’s electrical activity throughout the scan. These leads are essential because the CT scanner synchronizes its imaging acquisition with the most stable part of the cardiac cycle, a process called “gating,” to minimize motion blur.
The patient is positioned on a motorized table that slides into the center of the CT machine. Immediately prior to the scan, a sublingual medication like nitroglycerin may be given to temporarily widen the coronary arteries, further improving image clarity. During the acquisition, the contrast dye is injected, and the patient may experience a brief, warm, flushing sensation spreading throughout the body, which is a normal reaction. The technologist will provide specific instructions, requiring the patient to hold their breath for a short duration while the scanner rapidly captures the necessary images.
Interpreting the Results
The resulting CCTA images are analyzed by a radiologist or cardiologist to identify and characterize abnormalities within the coronary arteries. One primary finding is the Coronary Artery Calcium (CAC) score, also known as the Agatston score, calculated from a non-contrast portion of the scan. This score quantifies the amount of calcified plaque present; a score of zero indicates no measurable calcium, and a higher score correlates to a greater burden of disease.
The core result of the CCTA is the assessment of stenosis, which is the degree of narrowing in the artery caused by plaque buildup. The report details the location, severity, and composition of any plaque, differentiating between soft, non-calcified plaque and hard, calcified plaque. These findings are standardized using the Coronary Artery Disease-Reporting and Data System (CAD-RADS), which assigns a score from 0 (no disease) to 5 (complete blockage) to communicate severity. Results showing a high degree of stenosis, typically 50% or more, may lead to recommendations for further diagnostic procedures or intervention, while lower scores often guide treatment toward aggressive risk factor management.