Heart Tests – Heart Tests


Image of cardiac MRI courtesy of W. Patricia Bandettini, MD, NHLBI Division of Intramural Research

Heart imaging tests take pictures of your heart or its arteries or blood vessels to help your doctor see whether there are any problems.

Cardiac CT scan

A cardiac computed tomography (CT) scan, also called a “CAT scan,” is a painless, non-invasive imaging test that uses X-rays to take many detailed pictures of your heart and its blood vessels. Computers can combine these pictures to create a three-dimensional (3D) model of your whole heart.

This imaging test can help doctors find heart diseases or problems with the heart or blood vessels supplying blood to the heart or the rest of the body. This test may also be used to check the results of coronary artery bypass grafting or to follow up on abnormal findings from earlier chest X-rays. You may go to a medical imaging facility or a hospital for a cardiac CT scan. The scan itself usually takes only about 15 minutes. However, it can take more than an hour to prepare for the scan, including time to take medicines such as beta blockers to slow your heart rate or nitroglycerin to help dilate your arteries. Before the test, a healthcare provider will inject a contrast dye, often iodine-based, into a vein in your arm. This contrast dye highlights your blood vessels and creates clearer pictures. You may feel some discomfort from the needle or, after the contrast dye is injected, you may feel a warm flush briefly throughout your body or have a temporary metallic taste in your mouth.

The CT scanner is a large, tunnel-like machine that has a table. You will lie still on the table, and the table will slide into the scanner. Talk to your doctor if you are uncomfortable in tight or closed spaces to see if you need medicine to help you relax during the test. During the scan, the technician will monitor your heart rate with an electrocardiogram (EKG). You will hear soft buzzing, clicking, or whirring sounds when you are inside the scanner and the scanner is taking pictures. You will be able to hear from and talk to the technician performing the test while you are inside the scanner. The technician may ask you to hold your breath for a few seconds during the test.

Cardiac CT scans have some risks. In rare cases, the contrast dye may cause damage to the kidneys, particularly in people who have known chronic kidney problems. Your doctor or the imaging center may do a blood test to check your kidney function before the exam. In rare instances, some people may have an allergic reaction to the contrast dye. If you have a known allergy, you may still be able to receive contrast if you receive medicine ahead of time. There is a very slight risk of cancer, particularly in people younger than 40 years old who undergo multiple CT scans, because the test uses radiation.

Talk to your doctor and the technicians performing the test about whether you are or could be pregnant or are breastfeeding.

Rarely, people with lung diseases or heart failure may have breathing problems during cardiac CT scans if they are given beta blockers to slow their heart rates for this imaging test.

Coronary calcium scan

A coronary calcium scan is a CT scan of your heart that measures the amount of calcium in the walls of your coronary arteries. Buildup of calcium, or calcifications, are a sign of atherosclerosis or coronary heart disease.

A coronary calcium scan may be done in a medical imaging facility or hospital. The test does not use contrast dye and will take about 10 to 15 minutes to complete. A coronary calcium scan uses a special scanner such as an electron beam CT or a multidetector CT (MDCT) machine. An MDCT machine is a very fast CT scanner that makes high-quality pictures of the beating heart. A coronary calcium scan will determine a score that reflects the amount of calcium found in your coronary arteries, often referred to as an Agatston score. A score of 0 is normal. In general, the higher your score, the more likely you are to have coronary heart disease. If your score is high, your doctor may recommend more tests.

A coronary calcium scan has few risks. There is a very slight risk of cancer, particularly in people younger than 40 years old who undergo multiple CT scans. However, the amount of radiation from one test is similar to the amount of radiation you are naturally exposed to over one year. Talk to your doctor and the technicians performing the test about whether you are or could be pregnant.

Cardiac MRI

A cardiac magnetic resonance imaging (MRI) is a painless, noninvasive imaging test that uses radio waves, magnets, and a computer to create detailed pictures of your heart. No ionizing radiation is used in this type of imaging. This test can provide information on the type and seriousness of heart disease to help your doctor decide the best way to treat your condition.

Cardiac MRI can help your doctor diagnose heart diseases or problems with the blood vessels. Cardiac MRI can provide an accurate look at the heart muscle, heart chamber sizes and function, and connecting blood vessels. It is an excellent tool to look for scarring of the heart muscle like you might see in a heart attack, or inflammation of the heart as you might see with heart infection. Cardiac MRI may be performed as a resting study or used in combination with a stress medicine or exercise to look for low blood flow to the heart muscle. Cardiac MRI is also an excellent tool for evaluating tumors or clots in the heart and to help your healthcare provider monitor congenital heart disease or problems with your heart valves or aorta. Cardiac MRI may be used when images from other studies like an echocardiogram are not clear. It can also help clarify results from other imaging tests such as chest X-rays and chest CT scans.

Cardiac MRI may be done in a medical imaging facility or hospital. Before your procedure, a contrast dye to highlight your heart and blood vessels may be injected into a vein in your arm. Some cardiac MRI studies don’t require contrast. The MRI machine is a large, tunnel-like machine that has a table. You will lie still on the table and the table will slide into the machine. Talk to your doctor if you are uncomfortable in tight or closed spaces to see if you need medicine to help you relax during the test. You will hear loud humming, tapping, and buzzing sounds when you are inside the machine as pictures of your heart are being taken. You will be able to hear from and talk to the technician performing the test while you are inside the machine. Your heart rhythm will be monitored by an electrocardiogram, and your pictures will be coordinated with your heart beat. The technician may ask you to hold your breath for a few seconds multiple times during the test.

Cardiac MRI has few risks. In very rare cases, the contrast dye may cause an allergic-type reaction. Talk to your doctor and the technicians performing the test if you are or could be pregnant or are breastfeeding. If you are breastfeeding and need to receive MRI contrast, you may be instructed to discard your breastmilk for up to 2 days after the MRI study.

Tell your doctor if you have:

  • A pacemaker or other implanted device because the MRI machine can damage these devices or cause a metallic implant to move.
  • Had any prior surgeries, even if you do not know if metal was involved. Metal inside your body from previous surgeries (for example from clips or metal parts) can interfere with the MRI machine, cause the metal to move, cause artifacts in your images, or cause local heating. A lot of surgery-related metal is safe in the MRI machine, but it is important for the imaging team to carefully screen you ahead of time.
  • Metal on your body from piercings, jewelry, or some transdermal skin patches because they can interfere with the MRI machine or cause skin burns. Tattoos may cause a problem because older tattoo inks may contain small amounts of metal.

Carotid ultrasound

Carotid ultrasound is a painless imaging test that uses high-frequency sound waves to create pictures of the inside of your carotid arteries. Your carotid arteries are the major blood vessels that supply oxygen-rich blood to your brain. Carotid ultrasound can help detect plaque buildup in one or both of your carotid arteries. It can also see whether the buildup is blocking blood flow to the brain. If combined with Doppler ultrasound, this test can also show how blood is moving through your arteries.

Carotid ultrasound is usually done in a doctor’s office or hospital. This test uses an ultrasound machine, which includes a computer, a screen, and a transducer. The transducer is a handheld device that sends and receives sound waves.

You will lie on your back on an exam table for your test. The ultrasound technician will put gel on your neck where your carotid arteries are located. The gel helps the sound waves reach your arteries. The technician will move the transducer against different areas on your neck. The transducer will detect the sound waves after they have bounced off your artery walls and blood cells. A computer will use the sound waves to create and record pictures of the inside of your carotid arteries and to show how blood is flowing in your carotid arteries. Test results will help your doctor plan treatment to remove or stabilize plaque and help prevent a stroke.

Carotid ultrasound has no risks because the test uses harmless sound waves. They are the same type of sound waves that doctors use to create and record pictures of a baby inside a pregnant woman.

Nuclear heart scan

A nuclear heart scan is an imaging test that uses special cameras and a radioactive substance called a tracer to create pictures of your heart. This imaging test can detect if blood is not flowing to parts of the heart and can diagnose coronary heart disease. It also can check for damaged or dead heart muscle tissue, possibly from a previous heart attack, and assess how well your heart pumps blood to your body.

You may go to a medical imaging facility or a hospital for a nuclear heart scan. Your healthcare team will monitor your heart during this test with an electrocardiogram (EKG). They will take two sets of pictures, each taking 15 to 30 minutes. The first set of pictures is taken right after an exercise or medicine stress test because some problems happen only when the heart is working hard or beating fast. Shortly after the stress test, the healthcare provider will inject the tracer into a vein in your arm. You may bruise at the injection site. You will lie still on a table that slides through a tunnel-like machine as the first set of pictures is taken. The second set of pictures will be taken on either the same day or the next day after your heartbeat has returned to normal.

Nuclear heart scans have few risks. In rare instances, some people have a treatable allergic reaction to the tracer. If you have coronary heart disease, you may have chest pain during the stress test. Medicine can help relieve your chest pain. Talk to your doctor and the technicians performing the test about whether you are or could be pregnant.

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