Cardiac Computed Tomography Scan

A cardiac computed tomography (CT) scan is a non-invasive imaging test that uses X-rays and a computer to create detailed pictures of your heart and its blood vessels. It helps doctors look for problems like blockages in the arteries, assess heart structure, and plan treatments. This scan provides important information to help manage your heart health.

What is Cardiac Computed Tomography Scan?

A cardiac computed tomography (CT) scan is a non-invasive imaging test that uses X-rays and computer technology to create detailed, cross-sectional pictures of your heart and its major blood vessels. This test helps doctors see the structure of your heart, identify blockages, and check for other heart-related conditions.

A cardiac CT scan is a specialized type of X-ray that takes many pictures from different angles. A powerful computer then combines these images to create detailed views of your heart. These views can show slices of your heart, much like looking at slices of bread, allowing doctors to see inside the organ without surgery. This scan helps visualize your heart muscle, the four chambers of your heart, and the large blood vessels connected to it, especially the coronary arteries. The coronary arteries are the blood vessels that supply oxygen-rich blood to your heart muscle. By seeing these structures clearly, doctors can detect problems that might not be visible on other types of tests. Sometimes, a special dye called contrast material (or contrast dye) is injected into a vein during the scan. This dye makes your blood vessels and heart chambers show up more clearly on the images. The contrast material helps doctors identify areas of narrowing or blockages in the arteries, as well as other abnormalities.

Why it's ordered

Doctors often order a cardiac CT scan to investigate symptoms like chest pain or shortness of breath, which could signal heart problems. It is commonly used to detect coronary artery disease (CAD), assess heart valve issues, or plan for certain heart procedures, providing crucial details about your heart's condition.

One of the main reasons doctors order a cardiac CT scan is to look for coronary artery disease (CAD). This condition happens when the arteries that supply blood to your heart become narrowed or blocked by a buildup of fatty deposits, called plaque. The scan can show if plaque is present, how much there is, and if it's causing significant blockages. Your doctor might also use this scan to check for calcium buildup in your coronary arteries. This is known as a coronary artery calcium (CAC) score. A higher CAC score can indicate a greater risk of future heart problems. The scan can also help evaluate problems with your heart valves, which control blood flow through your heart, or issues with the aorta, the body's main artery. Cardiac CT scans are also important for planning certain heart procedures. For example, doctors may use the images to guide procedures like transcatheter aortic valve replacement (TAVR), a minimally invasive way to replace a heart valve, or to plan for treatments for irregular heartbeats (arrhythmias). It helps them understand the exact anatomy of your heart before they begin.

How to prepare

Preparing for a cardiac CT scan involves several steps to ensure clear images and your safety. You will typically need to avoid caffeine and nicotine for 12-24 hours and fast for a few hours before the scan. It's also important to discuss all your medications, allergies, and any potential pregnancy with your doctor beforehand.

Before your cardiac CT scan, your doctor or the imaging center will give you specific instructions. It is very important to follow these instructions carefully. You will usually be asked to avoid eating or drinking anything for about four hours before the test. However, you can typically drink water. You should also avoid caffeine and nicotine for 12 to 24 hours before your scan, as these can affect your heart rate and image quality. Tell your doctor about all medications you are currently taking, including over-the-counter drugs, supplements, and herbal remedies. If you have diabetes and take metformin, your doctor may advise you to stop taking it for a day or two before and after the scan, especially if contrast dye is used. Also, inform your doctor about any allergies, particularly to iodine, shellfish, or any previous reactions to contrast dye. If there is any chance you could be pregnant, you must tell your doctor immediately. Radiation from CT scans can be harmful to an unborn baby. You should also wear loose, comfortable clothing to your appointment and be prepared to remove any metal objects, such as jewelry, eyeglasses, or dentures, as these can interfere with the X-ray images.

What to expect during

During a cardiac CT scan, you will lie on a movable table that slides into a large, donut-shaped scanner. An intravenous (IV) line may be placed in your arm for contrast dye, and electrodes will monitor your heart rate. You will be asked to hold your breath briefly at times. The scan itself is usually quick and painless.

When you arrive for your scan, you may be asked to change into a hospital gown. A technologist will explain the procedure and answer any questions you have. They will place small, sticky patches called electrodes on your chest. These electrodes connect to an electrocardiogram (ECG) machine, which monitors your heart's electrical activity and helps time the CT scan images with your heartbeat. If your doctor has ordered a scan with contrast dye, an intravenous (IV) line will be inserted into a vein in your arm. The contrast dye will be injected through this IV line during the scan. You might feel a warm flush throughout your body or a metallic taste in your mouth when the dye is injected; these sensations are normal and usually pass quickly. You will lie on your back on a narrow, motorized table that slides into the opening of the CT scanner. The scanner is shaped like a large donut. The table will move slowly through the scanner while the X-ray tube rotates around you. You will hear humming or clicking noises. It is crucial to lie very still and follow instructions, such as holding your breath for short periods, to ensure clear images. The actual scan typically takes only 10 to 15 minutes.

Understanding your results

After your cardiac CT scan, a doctor specializing in medical imaging (radiologist) will analyze the detailed pictures and send a report to your referring physician. Your doctor will then discuss these findings with you, explaining what they mean in the context of your overall health and symptoms, and outline any necessary next steps.

Once your cardiac CT scan is complete, the images are sent to a radiologist. This medical doctor has special training in interpreting X-rays and other imaging tests. The radiologist will carefully examine all the pictures of your heart and blood vessels for any signs of disease or abnormalities. They will then prepare a detailed report summarizing their findings. This report is sent to the doctor who ordered your scan. Your referring doctor will then review the radiologist's report along with your medical history, symptoms, and the results of any other tests you have had. It is important to remember that your doctor is the best person to explain what your specific results mean for you. If your results are normal, it means no significant blockages, calcium buildup, or other heart problems were found. If abnormal findings are present, they could indicate conditions like coronary artery disease, issues with heart valves, or problems with the aorta. Your doctor will explain the nature and severity of any findings and discuss potential treatment options or further diagnostic tests that may be needed.

Risks

While generally safe, a cardiac CT scan carries a few potential risks. These include a small amount of radiation exposure, a rare chance of an allergic reaction to the contrast dye, and, even more rarely, kidney problems from the dye, especially for those with pre-existing kidney conditions. Your doctor will weigh these risks against the benefits.

One of the main concerns with any CT scan is exposure to radiation. A cardiac CT scan uses X-rays, which involve a small amount of ionizing radiation. The amount of radiation is similar to the natural background radiation you would be exposed to over several months. For most people, the diagnostic benefits of finding a serious heart condition outweigh this small risk. Doctors always aim to use the lowest possible radiation dose to get clear images. If contrast dye is used, there is a small risk of an allergic reaction. Most reactions are mild, such as hives, itching, or a feeling of warmth. More severe reactions, like difficulty breathing or a serious allergic response (anaphylaxis), are very rare. You should always inform your doctor and the technologist if you have any known allergies, especially to iodine or previous contrast dyes. Another rare risk associated with contrast dye is kidney damage, particularly in people who already have kidney disease. To help prevent this, you may be advised to drink plenty of fluids before and after the scan. If you have kidney problems, your doctor will discuss alternative tests or special precautions. Cardiac CT scans are generally avoided during pregnancy due to potential risks to the developing baby from radiation.

Frequently asked questions

Is a cardiac CT scan painful?

A cardiac CT scan is generally not painful. You might feel a slight pinch when the intravenous (IV) line is inserted for contrast dye. Some people experience a warm sensation or metallic taste when the dye is injected, but these feelings usually pass quickly. You will lie still on a table, and the scan itself is non-invasive.

How long does a cardiac CT scan take?

The actual scanning part of a cardiac CT scan is quite fast, often taking only 10 to 15 minutes. However, the entire appointment, including preparation, changing, IV placement, and post-scan instructions, can take longer, typically around 30 to 60 minutes in total.

Can I eat or drink before a cardiac CT scan?

You will usually need to fast (not eat) for about four hours before your cardiac CT scan. You can generally drink water. It's also important to avoid caffeine and nicotine for 12 to 24 hours before the test, as these can affect your heart rate and the quality of the images.

What is contrast dye and why is it used?

Contrast dye is a special liquid injected into a vein during some cardiac CT scans. It helps to highlight your blood vessels and heart chambers, making them show up more clearly on the X-ray images. This allows doctors to better identify blockages, narrowing, or other abnormalities in your heart's structures.

Is a cardiac CT scan safe if I'm pregnant?

Cardiac CT scans are generally avoided during pregnancy because the radiation exposure could potentially harm the developing baby. If you are pregnant or suspect you might be, it is crucial to inform your doctor immediately so they can consider alternative imaging methods if necessary.

What if I have a pacemaker or other implanted device?

Having a pacemaker or other implanted medical device is generally safe for a cardiac CT scan. Unlike MRI scans, CT scans do not use strong magnetic fields that could interfere with these devices. However, you should always inform your doctor and the technologist about any implanted devices you have before the scan.

Sources

• MedlinePlus — Cardiac Computed Tomography Scan
• Mayo Clinic — Cardiac Computed Tomography Scan
• Cochrane Library — Cardiac Computed Tomography Scan