The Coronary Computed Tomography Angiography (CCTA) is a non-invasive imaging test used for heart health assessment. This procedure uses X-rays and computer technology to create detailed, three-dimensional images of the coronary arteries, the blood vessels supplying the heart muscle. The primary purpose of CCTA is to visualize the inner walls of these arteries to detect atherosclerotic plaque buildup and identify any narrowing, known as stenosis, that could impede blood flow. CCTA provides valuable information that helps medical providers diagnose or rule out coronary artery disease.
Preparing for the Procedure
Successful CCTA imaging relies heavily on careful patient preparation. Patients are typically instructed to fast, avoiding solid food for about four hours before the scan to ensure optimal image quality and reduce the risk of nausea from the contrast dye. Maintaining hydration by drinking water is important, but sugary or alcoholic beverages should be avoided.
A strict restriction on stimulants is required; all caffeine and nicotine products must be avoided for at least 12 to 24 hours prior to the procedure. Stimulants increase the heart rate, which can lead to blurry, non-diagnostic images. A slow heart rate (60 to 65 beats per minute or less) is preferred, and patients may be given a beta-blocker medication to temporarily slow their heart rate before or during the test.
Patients must inform the medical team about any pre-existing conditions, particularly allergies to iodine or shellfish, as the procedure uses an iodine-based contrast material. Kidney function is reviewed because the contrast dye is cleared by the kidneys, and poor kidney health increases the risk of complications. Patients with diabetes taking metformin are often asked to temporarily stop the medication for 48 hours after the procedure to prevent a rare interaction.
How the Test is Performed
An intravenous (IV) line is inserted, typically into a vein in the arm, to inject the contrast material later in the procedure. Electrocardiogram (ECG) leads are placed on the chest to monitor the heart’s electrical activity and rhythm. This monitoring is crucial because the CT scanner uses the heart’s rhythm to time the X-ray pulses, capturing images when the heart is at its stillest.
The patient is positioned on the movable table of the CT scanner. Just before the scan begins, nitroglycerin may be administered under the tongue to temporarily widen the coronary arteries, making them easier to visualize. The iodinated contrast dye is then rapidly injected through the IV line, allowing the blood vessels to become brightly visible. Patients often feel a brief, warm flushing sensation and may experience a metallic taste in their mouth, both of which are normal and quickly subside.
The CT scanner table moves the patient through the gantry as the X-ray machine rapidly takes multiple cross-sectional images of the heart. During this quick, 10-to-15-minute scan, the patient is asked to hold their breath for about 15 seconds to prevent motion blur and ensure image clarity. The entire appointment, including preparation, usually takes between 45 minutes and two hours, though the actual scanning process is much shorter.
Understanding the Results
CCTA provides detailed insight into the condition of the coronary arteries. The images reveal the presence, location, and composition of atherosclerotic plaque, which can be categorized as soft (non-calcified), calcified (hard), or mixed. Visualizing soft plaque is a key advantage, as this type is often considered more prone to rupture and is not detected by a simple Coronary Artery Calcium (CAC) scan, which only measures hardened deposits.
Results are standardized using the Coronary Artery Disease Reporting and Data System (CAD-RADS), which categorizes the severity of the disease based on the degree of luminal narrowing, or stenosis. Stenosis is measured by comparing the narrowed segment to a normal section of the vessel. Categories range from mild (less than 50% narrowing), to moderate (50% to 69%), and severe (70% to 99%).
Minimal or mild disease (CAD-RADS 1 or 2) suggests a low risk of a near-term cardiac event and typically leads to preventative therapy. A moderate blockage may prompt further functional testing, such as a stress test, to determine if the narrowing restricts blood flow. Severe stenosis (CAD-RADS 4 or 5) often suggests a need for more invasive procedures like catheterization or revascularization. The report may also include modifiers describing the overall plaque burden and high-risk plaque features.
Safety Considerations
Safety considerations for CCTA relate primarily to the use of iodinated contrast dye and exposure to ionizing radiation. The contrast material carries a small risk of an allergic reaction, ranging from mild symptoms like itching to a severe systemic reaction. Staff are trained to manage these events, and patients with known contrast allergies may receive pre-medication.
The contrast dye also temporarily impacts kidney function, especially in individuals with compromised renal health. Kidney function is checked before the procedure, and patients are encouraged to drink plenty of fluids afterward to help flush the contrast from their system.
The CCTA test involves exposure to ionizing radiation from the X-rays, which carries a small increase in the lifetime risk of developing cancer. Modern CT technology uses techniques like prospective ECG triggering and lower tube voltage to significantly reduce the radiation dose, often achieving doses comparable to other common cardiac imaging tests. The radiation dose is generally low (around 10 millisieverts, or mSv), and this risk must be balanced against the benefit of accurately diagnosing coronary artery disease. Medical professionals follow the principle of keeping the radiation dose “As Low As Reasonably Practicable” (ALARP).