Congenital Heart Disease Tests

Updated on 2/11/2009

Most testing for congenital heart disease is performed on an infant or young child. However, if a fetus is at increased risk for congenital heart disease or a prenatal exam has uncovered a potential concern, testing may begin as early as the fifth month of pregnancy. Approximately 10 percent of heart defects don't manifest until adulthood; for these people, testing may not be begin until middle age.

A thorough physical exam and medical history are fundamental to the diagnosis of congenital heart disease. In the medical history, the physician will ask questions about patients' childhood--diseases and procedures they may have had, as well as the health of family members. During the physical exam, the doctor will listen to the heart and lungs for a heart murmur or other unusual sounds. Also the physician will note the condition of the neck veins, measure blood pressure and pulse, and check to see if there is swelling of the feet or ankles. Based on these findings, tests will be ordered to further evaluate the condition of the heart.

Despite the sophistication of many testing procedures and the valuable information they can provide, tests alone do not provide a diagnosis. The physician is ultimately responsible for interpreting test results, so it's vital that he or she has a good grasp of what each test can and cannot reveal in regards to the patient's condition. Before moving forward with a diagnostic test, especially an invasive test like a heart catheterization, review with your physician how the test results will add to his or her understanding of your condition.

This section has more on:

• Blood tests
• Computed tomography (CT or CAT scan)
• Chest X-ray
• Echocardiogram
• Electrocardiogram (ECG or EKG)
• Electrophysiology study (EPS)
• Heart (cardiac) catheterization
• Magnetic resonance imaging (MRI)
• Nuclear cardiac stress testing

Blood tests

Physicians rely on blood tests to help diagnose a wide variety of conditions as well as monitor the efficacy of treatments they've prescribed. Those who have or are suspected of having congenital heart disease often receive the following tests:

• Complete blood cell count (CBC) measures red and white cells, platelets, as well as other characteristics of the blood cells to identify potential blood disorders such as anemia (too few red blood cells) or infection (too many white blood cells).
• Blood cultures - These help identify any bacteria or other microorganisms that may be infecting the heart.
• Blood chemistry is evaluated to assess the functioning of the vital organs as well as the heart and may include lipid levels (cholesterol and triglycerides), coagulation studies to determine the amount of time for blood to clot, electrolytes to monitor kidney function, as well as many other parameters the selection of which are largely based upon the findings of the physical exam and medical history.

Computed tomography (CT or CAT scan)

Computed tomography is a specialized imaging technique that uses X-ray images collected from many different angles around the body to generate detailed cross-sectional images as well as three-dimensional images of the body's internal structures and organs. With congenital heart disease, CT scans are used to identify and delineate structural abnormalities in the heart, lungs, and major arteries.

The procedure is painless and requires the patient to lie as still as possible while a device resembling a giant donut rotates about the body. Called a gantry, it directs small doses of electromagnetic radiation toward the body from various angles. The different tissues absorb varying amounts of radiation. The radiation leaving the body is recorded inside the gantry and interpreted by a computer, which compiles the images for display on a monitor. Sedatives may be used on infants or toddlers having this procedure because movement can blur the image and lead to incorrect results.

Sometimes a contrast medium, or dye, is injected into a vein to help depict the blood vessels and structures of the heart during a CT scan. If a dye is used, patients typically fast for a few hours before the procedure. Although rare, the contrast medium involved in a CT scan may cause an allergic reaction, the most common of which is hives or a feeling of itchiness. In people with asthma, the allergic reaction may manifest as an asthma attack. In very rare instances, a patient may experience swelling in the throat or other areas of the body. If you experience hives, itchiness, or swelling in your throat during or after your CT scan, immediately tell the technologist or doctor.

The CT scan involves exposure to a small amount of radiation. For most patients, the benefits far outweigh the minor risks associated with exposure to this low level of radiation. However, pregnant women may prefer to postpone getting a CT scan until after they've delivered or chose alternative testing procedures. Individuals with pacemakers or internal cardioverter defibrillators who have been advised to avoid MRIs can safely have a CT scan.

Chest X-ray

In a chest X-ray, electromagnetic energy is used to create images of internal tissues, bones, and organs. A chest X-ray can show the size, shape, and position of the heart, and it can detect changes in the lungs related to any heart abnormalities. Chest X-rays are a routine part of any evaluation for congenital heart disease.

Getting a chest X-ray doesn't hurt. Before the test you will need to remove all clothing and jewelry from the waist up. Then you will be asked to stand against the plate containing the X-ray film and roll your shoulders forward while holding your arms at your sides so that they do not interfere with the picture. The radiologist or technician will ask you to take a deep breath and hold it as the X-ray picture is taken. Holding your breath fills your lungs with air and helps your heart and lungs to show up more clearly on the film.

An X-ray involves being exposed to a small amount of radiation. In most cases, the benefits derived from the X-ray greatly outweigh the slight increase in cancer risk posed by the exposure. However, women who may be pregnant should talk with their doctors about alternative testing procedures or special precautions that can be taken to minimize exposure to the developing fetus.

Echocardiogram (ECHO)

Echocardiography is an extremely useful tool for evaluating abnormalities within the heart. In fact, most heart problems can be diagnosed with ultrasound, avoiding the need for invasive heart catheterization for the vast majority of patients. Echos are used to:

• measure the dimensions and shape of the structures of the heart
• evaluate pressure gradients within the heart
• visualize blood flow and valve leakage
• evaluate the condition of the valves
• identify abnormal blood-flow patterns
• evaluate the pumping strength
• assess blood pressures in the arteries of the lungs

Echocardiography relies on ultrasound, the same technology used in fish locators on boats--and prenatal sonograms. A small device that looks like a microphone, called a transducer or probe, directs ultrasound waves into the chest. The returning sound waves are analyzed by a computer that generates images that can be viewed on a video screen. The information collected by the echocardiograph can be displayed three ways: The M-mode echocardiogram looks nothing like a heart. This abstract image is used to measure the size of various structures in the heart and the exact thickness of the heart muscle.

The 2-D echocardiogram provides a moving image that shows how well all the parts of the heart are working. These two-dimensional images offer a view of the heart as if its layers were slices in a loaf of bread.The Doppler echocardiogram helps doctors evaluate the blood-flow paths through the heart. You'll hear a "whoosh" sound during the procedure that represents blood flowing past the heart's various structures.

No preparation is needed for the standard echo known as a transthoracic echocardiogram (TTE). In this procedure, which usually takes one to two hours, a technician applies a watery gel to the chest and then slides the transducer across the chest to scan the heart from various angles. The technician monitors the electrical activity of the heart throughout the procedure using electrodes that are attached to the chest with sticky pads. In some cases, a contrast agent, akin to a dye, is injected into a vein to improve the images from the echo. Most patients say the procedure is painless, although some report slight discomfort from the pressure of the transducer on the chest. This section includes information on three other types of echocardiograms that may be used to evaluate congenital heart disease: the fetal echocardiogram, the transesophageal echocardiogram, and the stress echocardiogram.

Other types of echocardiograms

Other types of echocardiograms that may be used to evaluate congenital heart disease include the fetal echocardiogram, the transesophageal echocardiogram, and the stress echocardiogram.

Fetal echocardiogram. The structures of the heart in a developing fetus are evaluated using a fetal echocardiogram. This procedure is usually performed during the fifth month of pregnancy and poses no known risk to the fetus or mother. Doctors typically order a fetal echocardiogram if an embryo is believed to be at increased risk for developing a congenital heart defect or a prenatal exam has detected abnormal heart sounds in the developing fetus.

Transesophageal echocardiogram (TEE). For more detailed information about the heart valves and possible blood clots in the heart, a transesophageal echocardiogram or TEE may be necessary. In this procedure, the transducer is mounted on the tip of a 1/2 inch-diameter, flexible tube that is inserted through the patient's mouth down into the esophagus, the passageway that runs from the throat to the stomach. The advantage of the transesophageal echocardiogram is that it provides a more detailed image of the heart valves and blood flow because the esophagus is close to the heart.

Patients are asked to fast for at least eight hours before the test; ask your physician about taking medications. This procedure does not interfere with breathing, and patients are given a numbing medication and a mild sedative to make them more comfortable. Most patients rest comfortably during the procedure, which usually lasts between 15 and 20 minutes. Some individuals experience a minor sore throat following this procedure.

Stress Echocardiogram. A stress echocardiogram is done under conditions that increase the work of the heart, so pumping capacity and efficiency of the heart as well as any blockages of the coronary arteries can be evaluated. Patients undergoing a stress echo are asked to fast for three hours before the exam, wear comfortable clothing, and take medications as usual unless otherwise instructed.

The stress echo starts by obtaining images of the heart at rest. Then the technician will take additional images after the workload of the heart has been increased. For an exercise stress test, patients usually use a treadmill or a stationary bicycle to reach their peak exercise level. For patients who are unable to exercise, a medication is injected to simulate the effects of exercise on the heart, usually dobutamine. Dobutamine causes the heart rate to gradually increase. After receiving the drug, some people experience a slight flushing in the cheeks, a tingling scalp, and the uncomfortable feeling that their heart is beating faster and harder. Atropine is another medication that may be used but it has potentially serious side effects for people with glaucoma.

Although echocardiography uses ultrasound, which poses no known risk to the body, a stress test is not completely risk free. On rare occasions, a heart problem can occur during a stress test. To detect any problems that may arise, blood pressure and the heart's electrical activity are monitored continuously throughout the test. The technicians who administer the test are trained to treat potential complications that may arise.

Electrocardiogram (ECG or EKG)

An electrocardiogram (ECG or EKG), an electrical recording of the activity of the heart, is routinely performed to evaluate congenital heart defects. The ECG records the timing and duration of each electrical phase of the heartbeat. The ECG can provide clues about thickening of the heart muscle, structural abnormalities, heart rhythm abnormalities, inadequate blood and oxygen supply to the heart muscle, or enlargement of the heart's chambers--quickly, inexpensively, and with no risk to the patient. If the ECG indicates an abnormality, additional testing is usually needed to confirm a diagnosis.

In an ECG, the electrical activity of the heart is recorded by electrodes that are temporarily attached to the skin with sticky pads. The electrodes transmit the heart's electrical impulses to a device that records these impulses as wave-shaped lines on a scrolling paper or on a monitor. This output is called a tracing. Different waves represent different areas of the heart. The main components of the ECG tracing are:

• the P wave, representing electrical currents in the atria,
• the QRS complex, representing electrical currents in the ventricles
• the T wave, representing the electrical recovery period of the ventricles

An ECG can reveal the strength and duration of the electrical impulses in the heart. It also can show a deviation in the electrical firing sequence of the heart, which normally starts in the atria and proceeds to the ventricles.

The actual ECG reading takes only 30 to 60 seconds. The test requires no preparation on the part of the patient. Usually, 12 to 15 electrodes are attached to various parts of the body, including one on each arm and each leg and six across the chest. The remaining electrodes are attached at other sites in the chest, neck, and back. After the leads are attached, the readings are recorded. There is no discomfort associated with this test. This section includes information on other types of ECG used in the evaluation of congenital heart defects.

Other types of ECG

Other types of ECG used in the evaluation of congenital heart disease include:

Continuous or Ambulatory ECG. A Holter monitor is a portable ECG device that makes a continuous recording of the heart's electrical activity during a patient's daily routine. Usually worn for 24 to 72 hours, the Holter monitor, which is the size of a small deck of cards, can detect intermittent heart rhythm irregularities.

Event monitor. For irregular heartbeats that occur sporadically, the patient can carry a small, portable ECG device known as an event monitor. Event monitors may be the size of a small paperback novel, with electrodes that attach to the chest, or even as small as a credit card that merely needs to be placed upon the chest to pick up the electrical impulses. When symptoms arise, the patient turns on the event monitor to record the ECG. The recording can be transmitted across telephone lines.

Exercise ECG. Also known as a stress test, this procedure assesses how well your heart is working. It can detect coronary circulatory problems and abnormalities caused by insufficient blood and oxygen supply to the heart muscle. Rhythm abnormalities triggered by exercise may also be detected and used to identify exercise limits and develop an individual fitness program.

Minor preparations are required for an exercise test, usually involving diet restrictions. The exercise ECG is performed with the individual on a treadmill or stationary bike, so wear comfortable clothing and athletic shoes. The exercise portion of the test usually lasts five to 15 minutes; with the entire test lasting 30 to 40 minutes. The exertion level will increase gradually at regular intervals until the peak exertion level, as determined by the healthcare team, is met. Shortness of breath and sweating are normal, but be sure to tell the healthcare team if you experience chest pain, severe shortness of breath, dizziness or leg cramps. The ECG readings are recorded continuously before, during, and after exercise. Changes in blood pressure and exercise capacity are also recorded.

Your doctor may also want to measure oxygen consumption to determine how well the heart and lungs are working together. This requires wearing a nose clip to force you to breathe through your mouth and a special mouthpiece that measures the amount of oxygen you breathe during exercise. An exercise ECG carries a small risk because it involves increasing the workload of the heart. The chances of suffering heart problems during the test are remote. For instance, 48 individuals out of 10,000 people taking an exercise ECG experience a serious heart rhythm problem; 3.5 in 10,000 experience a heart attack. Moreover, the healthcare professionals administering the test are trained to diagnose and treat these kinds of complications appropriately and quickly.

Electrophysiology studies (EPS)

Electrophysiology studies use electrodes attached directly to the heart to collect detailed information on people with heart rhythm disorders, including those caused by heart valve defects, or on those whose electrocardiogram or other related tests rendered inconclusive results. These studies, which produce precise maps of the progression of electrical impulses through the heart, can be difficult to interpret and must be evaluated in light of all other medical information. Unlike the ECG, the electrophysiology study is an invasive procedure requiring heart catheterization.

Electrophysiology studies may take as long as four hours and involve using a catheter to place electrodes directly on the heart. Once the electrodes are in place, the physician stimulates the heart with tiny electrical impulses that cannot be felt. However, the impulses may trigger the arrhythmia that is causing your symptoms. This allows the physician to see where the arrhythmias are occurring and may help explain what is causing the irregular heartbeat. During the study the physician can also evaluate potential treatments for your particular arrhythmia, including medications and pacing devices.

As with other catheterization procedures, electrophysiology studies carry risk. In general, less than 1 of every 100 people who undergo an electrophysiology study experiences a complication. These include bleeding, bruising, blood clot, or infection. There also is a small risk of a stroke or a tear in the lining of a blood vessel occurring during catheterization. In addition, the heart may develop a severely abnormal heart rhythm, including ventricular fibrillation. The medical team is trained and prepared for handling this emergency.

Heart Catheterization (Cardiac Cath)

Heart catheterization, also called cardiac catheterization or cardiac cath, is used both to diagnose and treat heart problems. In heart catheterization, a thin tube is inserted into a blood vessel and snaked along inside the vessel to the heart.

Diagnostic testing for congenital heart disease using heart catheterization includes the following:

• Coronary angiogram - Also known as an arteriogram, the coronary angiogram is a valuable tool for confirming a defect that has shown up in a physical exam or during echocardiography. The test uses a contrast medium or dye to create detailed X-ray pictures of the structures inside the heart, particularly the arteries and vessels.
• Oxygen levels - Oxygen levels from different parts of the heart measured using cardiac cath can be used to identify abnormal blood patterns such as through a septal defect.
• Blood pressures. Blood pressure measurements from different parts of the heart are used to evaluate blood-flow patterns in the heart and lungs.
• Biopsy - Tissue samples, or biopsies, of heart muscle can be collected for microscopic evaluation in the laboratory to identify diseases of the heart muscle itself, like hypertrophic cardiomyopathy.
• Electrophysiology studies - Heart catheters are used to place electrodes directly on the heart to collect detailed information on the electrical activity of the heart.

Cardiac cath involves guiding an instrument into the heart; therefore this procedure is done in a hospital. The length of the stay depends upon the type of procedure being performed and the medical condition of the individual. An otherwise healthy person can have a diagnostic procedure as an outpatient. For people with other health concerns or who are undergoing more extensive testing or treatment, the hospital stay may be two to three days or longer. The cardiologist will provide specific guidance about preparing for the procedure, including instructions on fasting, use of medications, and showering before arriving at the hospital.

Although catheterization itself only takes about 30 minutes, preparation for the procedure takes two to three hours. Preparation includes having blood taken, having an ECG if one has not been done recently, and discussing the details of the procedure with a member of the catheterization team. The insertion site is then prepared by shaving the hair from a small area in the groin or the inside of an elbow and an intravenous line is started to administer fluids and medications as needed during the procedure. Monitoring equipment including an ECG and blood pressure are also used throughout the procedure. At this time, a mild sedative may be administered to help the patient relax.

Catheterization is done in a specialized suite that is similar to an operating room and is equipped with an X-ray machine. In adults, heart catheterization is done under a local anesthetic with the patient remaining awake throughout the procedure. Typically, the procedure starts with the physician inserting a needle into a small artery of the groin, and snaking a sequence of wires and tubes up through the artery into the heart.

Once the catheter is positioned in an area of interest, the cardiologist will perform various tests and procedures. A biopsy may be collected for microscopic evaluation of the heart muscle fibers. Often, blood oxygen levels and blood pressure readings are measured; the cardiologist may also inject a contrast dye through the catheter to make the heart chambers or blood vessels more visible in X-ray images. This often makes patients feel suddenly warm or flushed for about 30 seconds.

After the physician has all the information needed, the catheter is removed, the insertion site is stitched or bandaged, and the patient will be taken to a recovery room for 30 to 60 minutes before being moved to a hospital room. Usually, activity can gradually resume after resting for one to six hours, depending on the site, number, and size of catheters used. But patients should not drive the day of the procedure. Thanks to the sedating medications and painkillers administered to the injection site, patients undergoing this procedure generally don't experience much pain or discomfort.

The most common complication of heart catheterization is bruising at the site where the catheter was inserted. Other less frequent complications include infection of the insertion site, irritation of the nerve fibers causing a tingling feeling (this is typically temporary), and bulges or even blockage of the artery at the insertion site.

Much more rare complications include irregular heart rhythms, stroke, and even cardiac arrest. The overall risk of developing one these more serious complications is between 1 in 100 and 1 in 1,000 for all individuals undergoing catheterizations. The risk of complications depends upon overall health, the tests being performed, and the skill of the cardiologist. Critically ill patients who undergo heart catheterization on an emergency basis are at highest risk for serious complications.

Magnetic resonance imaging (MRI)

MRIs use magnetic fields and radio waves to create three-dimensional images and two-dimensional cross-sections of the body. The images produced by MRI are similar to an X-ray, but show more information about the soft tissues of the body for a more detailed picture. This picture more clearly defines subtle abnormalities in the anatomy of the heart and great vessels.

MRI machines have tubes that are big enough for a patient to fit inside. Radio waves and a strong magnetic field produced by electrical currents traveling through coils within the shell of the tube are directed toward the body during an MRI scan. The body responds by emitting weak energy signals that are detected by the MRI machine. A computer converts these signals into three-dimensional images that can be manipulated to show any two-dimensional cross-section.

Before the test you must remove all accessories and clothing containing metal, including jewelry, metal fasteners, dentures, wigs, and hearing aids. Metal objects may interfere with the magnetic field of the MRI, affecting the quality of the image.

An MRI exam is painless and generally lasts between 30 and 60 minutes. The procedure involves lying on a table that slides into the tube. Movement can blur the images, so it is important to remain still. Often patients will be offered headphones or earplugs to help block out the loud tapping and thumping sounds made by the machine. The space inside the tube is quite narrow, and some patients may feel claustrophobic.

Magnetic resonance angiography (MRA) is one of the newer uses of MRI. For this test, a contrast agent, akin to a dye, is injected into the arm or leg through an intravenous (IV) line. The dye makes it easier to visualize the heart and blood vessels. One advantage of the MRA is that it uses contrast dyes that are less likely to cause allergic reactions than those used during computed tomography (CT or CAT Scans).

There are no known risks from the magnetic fields and radio waves produced by MRI machines. However, people who have pacemakers, cardioverter defibrillators, or other metal-containing objects inside their bodies cannot get MRIs. Also, the affects of magnetic fields on fetuses are not well understood, so getting an MRI may not be advisable for pregnant women.

Nuclear Cardiac Stress Testing

Patients with congenital heart disease may have a nuclear cardiac stress test to evaluate how well the heart muscle is being supplied with blood and how well the ventricles are working. This test is done during exercise or with a medication that stresses the heart. The results are used to determine best alternatives for treatment.

In a sense, nuclear testing is the opposite of X-rays. X-rays direct radiation into the body to create images; in a nuclear scan, the radiation comes from within the body to create the image. Trace amounts of thallium, a substance that emits gamma radiation, are injected into the bloodstream, usually through an IV in the arm. The thallium travels in the blood through the arteries and veins of the heart muscle. A camera that detects gamma radiation is used to create images of the heart that are interpreted by nuclear medicine specialists.

Preparing for the test includes some dietary restrictions, including avoiding caffeine for 24 hours before the test. You should wear comfortable clothing and shoes. The test can last two to four hours and begins with the insertion of an IV line for administering the thallium and attaching electrodes to the skin for an ECG. During the test, two sets of images are captured; one at rest, and the other when the heart is stressed. Each set of images takes about 20 minutes to complete and requires the patient to lie as still as possible while the gamma camera rotates about the chest.

Thallium stress tests rely on either exercise -- treadmill or stationary bicycle -- or medication to stress the heart. Several medications can be used to increase the workload to the heart; talk to your healthcare provider about the best medication for you. The most common side effects from the medication are feeling flushed and feeling that your heart is beating faster and harder.

All stress tests carry a small risk because they involve increasing the workload of the heart. The chances of suffering heart problems during the test are remote and the healthcare professionals administering the test are trained to diagnose and treat the complications appropriately and quickly. A thallium stress test involves only a small dose of radiation and poses no greater radiation exposure risk than a conventional X-ray.