During the evaluation process, a pediatric cardiologist will perform several diagnostic tests. An echocardiogram is the most informative non-invasive test for evaluating the degree of heart dysfunction. The following tests are performed when a child is awake.
Also known as a chest radiograph, chest X-rays generate images of the lungs to determine if there is any fluid accumulation or abnormalities in the lungs. The x-ray also shows the size and shape of the heart to determine if the heart is enlarged and whether there is congestive heart failure.
Often abbreviated to CT scan or CAT scan, this is an X-ray procedure that combines multiple X-ray images to generate three-dimensional images of the heart and its blood vessels. Detailed pictures of the beating heart provide information on the structure and function of the heart.
Echocardiogram & Doppler Ultrasound
An echocardiogram (echo) uses high frequency sound waves to produce moving images of the beating heart. These cross-sectional views allow the cardiologist to measure muscle thickness, chamber size, pumping ability (contractile force and blood filling), and valve movement. The echo also estimates the pressure inside the heart chambers and vessels.
A doppler ultrasound is performed with the echocardiogram and shows color-coded images of blood flow within the heart. The images are used to evaluate cardiac blood flow, measure the heart’s contraction, and check for blood flow obstruction or a leaky valve.
An electrocardiogram (EKG) records the heart's electrical activity through electrode patches placed on the child's limbs and chest wall. The EKG records the heart rate pattern and can indicate whether the heart is enlarged, thickened, or has an abnormal heartbeat. Some children with a normal echocardiogram but abnormal EKG have a genetic mutation for cardiomyopathy and may develop the disease later in life.
Exercise Stress Test
This test is usually performed in children above age 5 to determine if the heart pumps enough blood to meet the body's increased need for oxygen. During an exercise stress test, the child walks on a treadmill or pedals a stationary bike, and the child's blood pressure, heart rhythm, and breathing are measured at different levels of exertion. The test helps to determine the amount of exercise that a child with cardiomyopathy can tolerate when the heart is under exertion. In cases where a child does not respond well to medication, a stress test can help predict the need for a heart transplant.
A Holter monitor is an external device that is worn at home and continuously records the heartbeat for 24 to 72 hours through electrode patches placed on the skin. The data that is recorded on a tape cassette is used to identify any irregular and life-threatening heart rhythms. The cardiologist will determine the length of recording time, but the test can be extended to 21 days if needed.
Magnetic Resonance Imaging
Magnetic Resonance Imaging (MRI) is a radiation-based imaging procedure that looks at the size, shape, and structure of the heart. It also checks for any lung abnormalities. The three-dimensional images of the heart and blood vessels provide information on the heart’s function and flow dynamics. In ARVC cases, MRI is used to differentiate fatty deposits from muscle tissue within the heart walls since an echocardiogram may fail to identify any heart abnormality.
Multiple Gated Acquisition (MUGA) Scan
Also known as radionuclide ventriculogram, this test evaluates the pumping function of the ventricles (lower chambers of the heart). It is similar to an echocardiogram but more accurately measures the amount of blood the heart pumps or "ejects" with each contraction. It also measures how quickly blood is ejected. Radioactive substance is injected into a vein that flows to the heart to produce a moving image of the beating heart. This provides a detailed picture of the heart chambers and its functioning and is helpful for diagnosing heart failure.
Myocardial Perfusion Test
Following an exercise stress test, a small amount of radioactive substance is injected into the bloodstream to generate images of blood flow to the heart. The test is then repeated after rest for comparison. The procedure shows where the heart is not receiving an adequate supply of blood.
Pulmonary Function Test
In advanced stages of cardiomyopathy, lung circulation may be affected, and a pulmonary function test (PFT) may be requested to measure lung function. A child breathes into a mouthpiece that is connected to a spirometer that records the amount of air the child breathes in and out over a period of time.