Common Tests for Congenital Heart Defects

To ensure you receive the best appropriate care, you cardiologist may recommend a series of tests to measure your heart's function. Before completing any of the following tests, the cardiology staff will discuss with you what the test entails and what it measures. Once the test is completed, your cardiologist will explain the results and whether future care is needed.

Common tests for heart function include:

Electrocardiogram (ECG or EKG)

An electrocardiogram (ECG or EKG) is a test that measures the electrical activity of the heartbeat. An ECG gives two major kinds of information. First, by measuring time intervals on the ECG, a doctor can determine how long the electrical wave takes to pass through different parts of the heart. Finding out how long a wave takes to travel from one part of the heart to the next shows if the electrical activity is normal or slow, fast or irregular. Second, by measuring the amount of electrical activity passing through the heart muscle, a cardiologist may be able to find out if parts of the heart are too large.

Although ECG has "electro" in its name, it doesn't send electricity into the body. Instead, it receives tiny electrical impulses that the beating heart makes and records them in a zigzag pattern on a moving strip of paper.

The test is often performed by a technician who will place stickers on your arms and legs and over the front of the chest. The stickers are then connected to separate wires or leads that connect to the ECG machine. Once the leads are placed, the test is recorded in seconds.

Learn more detailed information about ECGs.

Chest X-rays

The chest X-ray gives the cardiologist information about your lungs and the heart's size and shape. The amount of radiation from a chest X-ray is extremely small and doesn't cause any long-term side effects.

Learn more detailed information about chest X-rays.


An echocardiogram is an ultrasound movie of the inside of the heart. It can detect nearly every congenital heart defect or any problem of the heart muscle function.

The test is often performed by a specialized technician called a sonographer, or by a physician. The test requires placing a few stickers, like those used for the ECG, on your chest to record the heart rhythm. The sonographer will place a special ultrasound device called a probe on the front of your chest, upper abdomen and the root of the neck to record pictures of the heart. The sonographer will make many adjustments in the ultrasound machine during the study to get the clearest pictures possible. An echocardiogram usually takes 40-60 minutes to perform.

Cardiac Catheterization and Angiogram

A cardiac catheterization is a procedure that allows the cardiologist to get direct information about the blood pressures and patterns of blood flow within your heart. An angiogram is an X-ray movie that's taken while contrast, a special fluid that's visible by X-ray, is injected into a cardiac chamber or major blood vessel.

Your cardiologist or nurse will explain the reason for this procedure and how the information obtained from the test will help in your care. They will also explain the test's possible risks, which fortunately are rare. After you've heard about the test and have had a chance to ask questions, you'll be asked to sign a consent form to have the test. Since a catheterization and angiogram require special X-ray equipment that's only found in hospitals or large medical facilities, you will usually have to schedule the test in advance.

Patients may be admitted to the hospital on the day of the catheterization or the day before. For several hours before the catheterization, you'll be told not to eat or drink anything. Before the test is done, you may be given a sleeping medicine by mouth or in a small shot under the skin. An intravenous line (IV) is sometimes placed in one of the veins. During the catheterization a team of nurses, doctors, and technicians will care for you. The catheterization test usually causes little discomfort.

The catheterization involves placing small IV tubes in the vein and artery of a leg, arm or the neck. Through the special IV tubes the cardiologist can pass thinner tubes (called catheters) into the circulation. Catheters are small, hollow plastic tubes that are the size of spaghetti noodles. The doctor will slowly move the catheter through the circulation until it reaches the heart. From there, the doctor can pass the catheter to different chambers of the heart and to the veins and arteries connected to the heart. Your cardiologist can learn very important information about your heart condition from the blood samples and blood pressures measured through the catheter at different places in the circulation.

Cardiologists usually perform angiograms during catheterization. This is done by injecting special fluid, called dye or contrast, through the catheter into a blood vessel or a chamber of the heart. Since the dye is visible by X-ray, an X-ray movie of the circulation can be recorded. An angiogram requires much more X-ray than is needed for a simple chest X-ray. For this reason the test is performed only when it's definitely necessary for your care. Be reassured that many studies have been done that show no long-term effects in people who had cardiac catheterization and angiography.

Sometimes doctors can treat a heart defect during the cardiac catheterization. This is called an interventional or therapeutic catheterization. These treatments include opening up a hole in the wall between the upper chambers, opening up a blocked valve or vessel, plugging off the unnecessary vessel or closing unnecessary holes in the heart. Your cardiologist will discuss these treatments with you before the catheterization.

After the catheterization and angiogram, your medical team will remove the small catheter tubes and IV line from your leg or arm and place a pressure bandage over the area. They will move you to the recovery room after the test is completed and observe you for several hours before discharging you to go home or admitting you to the hospital for more testing and/or observation. After the catheterization, your cardiologist will discuss the results of the test with you.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging is another way to take clear pictures of the heart and measure heart function. The MRI uses painless magnet waves to evaluate the heart and the blood vessels connected to the heart and lungs. Often your medical team will need to place a small IV in your hand.

The test usually takes 30-60 minutes to perform, and you must be perfectly still for the test. During the test you will lie on a table within the magnet. Most of your body will be within a small tunnel in the center of the magnet. This can be disturbing even for adults, but many centers have special headphones and video masks that can help to keep you calm during the test. If needed, your cardiologist will give you medicine to minimize any anxiety during the test.

Sometimes the test is done instead of or in addition to the cardiac catheterization and angiogram. Your cardiologist will decide if you need either test or both.

Learn more about Magnetic resonance imaging (MRI).

CT (Computerized Tomography) of the Heart

The CT scan uses multiple X-ray images to take an X-ray movie of the heart and lungs without placing catheters into the circulation. Like the MRI, this test sometimes takes clearer pictures than an angiogram. The test only requires a simple IV in the hand, and it can be done more quickly than an MRI. Unlike MRI imaging, the CT scan uses about the same amount of radiation as is needed for an angiogram.

Transesophageal Echocardiogram (TEE)

A transesophageal echocardiogram is a special type of ultrasound "movie" of the heart that produces much clearer pictures than a standard echocardiogram that's performed on your chest. To complete the study, the doctor places a special long tube with a small ultrasound "camera" on the end, called a TEE probe, in your esophagus, while you are sedated.

Your cardiologist may recommend a TEE when the standard echocardiogram isn't clear enough to make the suspected diagnosis or if you are having heart surgery so the surgeon and anesthesia team have more information to guide treatment after surgery. This occurs most frequently in adolescent and adult patients. The TEE also helps the surgical team determine whether the procedure has been successful or if additional repair is needed prior to leaving the operating room.

The risk of a TEE is minimal.

Learn more about Transesophageal Echocardiogram (TEE).

Special Heart Rhythm Testing

Holter Monitor

Holter monitor is a way to record every beat of your heart for 24 hours. Your cardiologist my recommend a Holter monitor to make sure that you aren't having any dangerous heart rhythms that might need more treatment.

A Holter monitor is a small recorder that is attached to your body by stickers similar to those used to make an electrocardiogram. It doesn't hurt, but sometimes the stickers can irritate the skin during the recording time. You will keep a diary of events during the 24-hour period that you wear the monitor. This record will help the doctors know when you are active, sleeping or having any symptoms that might be caused by a heart rhythm problem.

Once you have completed the recording, you will return the recorder to the heart center for review. A technician will process the information from the recorder for your cardiologist to review.

Since a Holter monitor is usually only worn for 24 hours, it's particularly helpful when you are having symptoms that are happening at least once a day. If symptoms are happening less often, your doctor may recommend an event monitor instead.

Download a printable Holter Monitor Diary (PDF).

Learn more about Holter Monitors.

Event Monitor

Event monitoring is a way to record the heart rhythm when your symptoms occur less than once a day. The event monitor is a recorder that's even smaller than a Holter recorder. You will wear it for most of each day — typically for 30 days at a time. The monitor is always recording, but not saving. When you have a symptom, you'll push a button on the recorder, which will save the rhythm just at that time and sometimes for a brief time before the button was pushed. When a recording has been made, you’ll send it using your mobile device to either the doctor’s office or a monitoring company that works with your doctor. You’ll be told how to do this.

Implantable Event Recorder

An implantable event recorder, which is also known as an implantable loop recorder, is a device that can record your heart rhythm for up to 14 months. This device is placed under the skin through a minor operation. This is the best way to record very serious rhythm problems that may be happening rarely. The recorder records certain heart rhythms automatically and when you or your child places a special activator over the device. Your cardiologist will use a special instrument to display and print the heart rhythms that the recorder saved.

Learn more about Cardiac Event Recorders.

Pacemaker/ICD Transmission

Patients who have pacemakers and ICDs routinely send a rhythm strip or a recording to check pacemaker/ICD function. A new technology allows ICD and pacemaker patients to send all their device information, including settings and recordings of arrhythmias, to their doctors using mobile devices.

Learn more about Devices for Arrhythmias.

Exercise Stress Testing

Exercise stress testing is a test of your heart rhythm and stamina while you exercise. You may run on a treadmill at standard speeds and ramps or ride a stationary bike at a steadily increasing resistance, while connected to ECG leads, which continually record your heart rhythm. In some centers you may also need to breathe into a tube so the amount of oxygen you use can be measured. This gives information about how well the heart works.

The stress test gives information about the effect on exercise on your blood pressure, heart rate, heart muscle and heart rhythm. If you have symptoms during exercise, this test will help to recreate them to see whether they are caused by the heart.

The test takes about 10-15 minutes to set up, 10-15 minutes to do and an additional 10-15 minutes of observation afterward. If you're scheduled for the test, you should bring gym clothes and sneakers appropriate for jogging.

Learn more about exercise stress testing.

Electrophysiology (EP) Study

An electrophysiology study is a specialized cardiac catheterization that looks at the heart's electrical or rhythm function instead of its blood flow. The heart's rhythm function is what controls the start of each heartbeat and controls the heart rate.

Your doctor may require an EP study to fix an abnormal fast rhythm problem or to assess the potential for developing abnormal rhythms (arrhythmias) that may need treatment with medication or surgery.

Learn more about Electrophysiology Studies (EPS).