In Duchenne, the heart is already affected before heart symptoms appear (cardiomyopathy). That is why it is critical to have the heart checked every year starting at diagnosis. The tests used to measure heart function include a cardiac MRI, echocardiogram, and electrocardiogram (ECG/EKG).
It is estimated 30-50% of carriers may develop heart problems as well. It is recommended that all female carriers have an evaluation with a cardiologist and have an echocardiogram (heart ultrasound) performed, first in their late teens/early 20s and if normal, repeated every 3-5 years. If cardiac changes are found, carriers may need to have more frequent exams and additional testing.
Cardiac MRI uses a powerful magnetic field to produce very detailed pictures of the heart. These pictures are used to measure the size and thickness of the heart, as well as how the heart squeezes and relaxes. While both the echocardiogram and the cardiac MRI are able to measure the same things, the images from the MRI are much more precise and are measured by the computer, rather than a person. In addition, scarring within the heart muscle (fibrosis) is able to be seen only on cardiac MRI. If cardiac MRI is appropriate for you, and is available, it is a superior diagnostic tool over an echocardiogram.
What to expect
- Your will lie on a special bed that moves into the machine. It is important that you are still so the technician can get good pictures of your heart. If you feel that you will be unable to lie completely still during the MRI, discuss other options with the medical staff.
- People with Duchenne should not receive anesthesia for a cardiac MRI. If you require anesthesia, discuss with your cardiologist whether echocardiogram might be a better mode of imaging the heart.
- Although the machine makes loud noises, it will never touch you and does not hurt. You can wear earplugs or headphones to drown out the noise.
- The test takes approximately 20 to 45 minutes to complete.
- You will need an IV to receive gadolinium dye before the MRI so it can circulate through the heart muscle. If there are areas of fibrosis within the heart muscle, these areas will “light up” and stay enhanced longer. This is called the “late gadolinium enhancement” and is diagnostic for cardiac fibrosis (scarring of the heart).
Results of the Cardiac MRI
Cardiac fibrosis may be an early sign of cardiac dysfunction. Cardiac medications should be started with evidence of cardiac fibrosis and/or dysfunction. Annual cardiac MRIs will help your cardiologist track changes to the heart function and fibrosis.
An echocardiogram uses a Doppler wand to obtain a sonogram, or ultrasound, picture of the heart. The wand picks up echoes of sound waves as they bounce off different parts of the heart. These echoes are seen as moving pictures, which are used to measure the size and thickness of the four chambers and walls of the heart, and also how well the heart squeezes and relaxes.
What to expect
- The sonographer will put three stickers on your chest or arms, called electrodes. These stickers record your heartbeat during the test.
- Next, the sonographer will put some jelly on your chest and belly so the probe can move easily. The room will need to be darkened so the sonographer can see pictures of your heart.
- The echocardiogram takes about 30 minutes to an hour to complete. A parent or care provider will be able to stay with you during the test.
Results of the echocardiogram
An echocardiogram allows your cardiologist to look at the size and thickness of the four heart chambers and walls of the heart. It can also show them how well the heart squeezes and relaxes as well as how the blood flows through the heart. An echocardiogram is not able to show scarring (fibrosis) within the heart muscle like the cardiac MRI can.
A cardiologist will need to “read” the images that the sonographer took, and take measurements that they need. Due to a cardiologist taking these measurements, and not a computer, the same measurements may be slightly different each time the test is done. For this reason, slight differences in measurements are usually not significant. It is important to have an echo (if a cardiac MRI is not appropriate) at least once a year so your cardiologist can follow your results.
An electrocardiogram, also known as an ECG or EKG, checks heart rate (how fast the heart beats) and rhythm (how regularly the heart beats). An electrocardiogram has stickers (electrodes) that stick to your chest and measure the rate and rhythm of the heart. An ECG/EKG does not hurt and only takes a few minutes to complete.
If your cardiologist is concerned you may be having abnormal heart rhythms, they may order a Holter monitor test. This is a portable ECG/EKG that is worn for 24 hours or longer at home. The Holter monitor is used to watch the heart rate and rhythm while doing normal activity. Your cardiologist is then able to look at what your heart rhythm looks like over an extended period of time.