What is a Cardiac CT?
A cardiac computed tomography (CT) scan is a painless, non-invasive imaging test that uses X-rays and computer technology to create detailed pictures of your heart and blood vessels. Unlike traditional X-rays, CT scanning creates three-dimensional images that allow doctors to see the heart from multiple angles.
The test is particularly useful for detecting coronary artery disease, evaluating the heart's structure, and identifying problems with heart valves, the aorta, and other major blood vessels. It can also measure the amount of calcium in the walls of the coronary arteries, which can indicate the presence of plaque buildup.
Types of Cardiac CT Scans
There are several types of cardiac CT scans, each designed to evaluate different aspects of heart health:
Common Types
- Coronary CT Angiography (CCTA): Uses contrast dye to create detailed images of the coronary arteries, showing blockages or narrowing
- Calcium Scoring (Coronary Calcium Scan): Measures the amount of calcium deposits in coronary arteries without contrast dye
- CT Angiography of Great Vessels: Evaluates the aorta and other major blood vessels
- Cardiac Structure and Function CT: Assesses heart chambers, valves, and overall cardiac anatomy
Why You Might Need This Test
Your doctor may recommend a cardiac CT scan for various reasons:
- To diagnose coronary artery disease or assess its severity
- To evaluate chest pain or other symptoms that might indicate heart disease
- To check for calcium deposits in coronary arteries (risk assessment)
- To plan treatment before a heart procedure
- To evaluate heart anatomy before heart valve surgery
- To check for problems with the aorta, such as aneurysms or dissections
- To assess the heart and blood vessels before or after surgery
- To evaluate the function of heart valves
- To investigate the cause of heart failure symptoms
- As an alternative to invasive coronary angiography in some cases
Preparing for Your Cardiac CT
Proper preparation helps ensure the best possible images. Your healthcare team will provide specific instructions, but general preparation typically includes:
- Avoid caffeine for 12 hours before the test (coffee, tea, soda, chocolate, energy drinks)
- Avoid eating for 4 hours before the test, though you can usually drink water
- Tell your doctor about all medications you're taking; you may need to hold certain medications
- Inform your doctor if you have kidney problems, diabetes, asthma, or allergies (especially to contrast dye or iodine)
- Let them know if you're pregnant or might be pregnant
- Remove jewelry and metal objects before the scan
- Wear comfortable, loose-fitting clothing without metal fasteners
What to Expect During the Test
Understanding what happens during a cardiac CT can help ease any anxiety about the procedure:
The Procedure
- Duration: The entire process typically takes 30-60 minutes, though the actual scanning takes only 10-15 minutes
- Position: You'll lie on your back on a narrow table that slides into the CT scanner (a large, donut-shaped machine)
- Heart rate control: You may receive medication (beta blocker) to slow your heart rate for clearer images
- Electrodes: Sticky patches placed on your chest will monitor your heart rhythm during the scan
- Contrast dye: If needed, contrast material will be injected through an IV in your arm, which may cause a warm sensation
- Breath holding: You'll need to hold your breath for a few seconds while images are taken
- Communication: You can hear and speak with the technologist throughout the test via intercom
After the Test
After your cardiac CT scan, you can typically resume normal activities immediately. If you received contrast dye, you'll be encouraged to drink plenty of water to help flush it from your system.
A radiologist will analyze the images and send a detailed report to your doctor, usually within a few days. Your doctor will then discuss the results with you and explain what they mean for your heart health and treatment plan.
Risks and Limitations
While cardiac CT is generally safe, there are some considerations to keep in mind:
- Radiation exposure: CT scans use X-rays, which involve exposure to radiation. The amount is small and considered safe, but repeated scans should be avoided when possible
- Contrast dye reactions: Some people have allergic reactions to contrast dye, ranging from mild (itching, rash) to severe (difficulty breathing)
- Kidney function: Contrast dye can affect kidney function, especially in people with existing kidney problems
- Not suitable for everyone: People with irregular heart rhythms or very high heart rates may not get optimal images
- Cannot evaluate function: While CT shows structure well, other tests may be needed to assess how the heart functions
Understanding Your Results
Your doctor will explain your cardiac CT results in detail. For coronary calcium scans, results are given as a calcium score:
- 0: No calcium detected (low risk of coronary artery disease)
- 1-99: Mild disease (low to moderate risk)
- 100-399: Moderate disease (moderate to moderately high risk)
- 400 and above: Severe disease (high risk of heart attack)
Interpreting Angiography Results
For coronary CT angiography, results will indicate whether there are any blockages in your coronary arteries, their location, and severity. Based on these findings, your doctor will recommend appropriate treatment, which might include lifestyle changes, medications, or procedures to improve blood flow.