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Tests and Services

Cardiac MRI


Children’s National Heart Institute is one of only a few pediatric programs to have a Cardiac MRI program run jointly by a pediatric cardiologist and a pediatric cardiac radiologist. By working together, these physicians are able to capture anatomic and physiologic details that were previously unattainable. The study is performed without radiation exposure, and can yield high resolution images of the moving heart and vascular structures that are not limited by body size or other anatomic constraints. In addition to improved visualization of complex anatomy, cardiac MRI can also be used to accurately measure hemodynamic parameters such as heart size and function, cardiac output, blood flow volumes, and pressure gradients. Cardiac MRI studies typically require 60-90 minutes to perform, and young children or other individuals who have difficulty remaining still may require sedation.

MRI is used to diagnose congenital heart defects and provide noninvasive evaluation for complex conditions, such as tetralogy of Fallot, coarctation of the aorta, certain rhythm abnormalities, cardiomyopathies, and patients with single ventricle anatomy. MRI also is used extensively in older adolescents and adults with congenital heart disease to obtain a more complete noninvasive cardiac evaluation, which can sometimes be limited with echocardiography due to body size.

Types of cardiac MRIs offered at Children’s include:
  • Sedated and non-sedated
  • Anatomic imaging
  • Physiologic studies
  • Perfusion imaging
Magnetic resonance imaging is one of the fastest growing diagnostic tools in pediatric cardiology. Children’s uses this emerging technology to produce very accurate images of the inside and outside of the heart, allowing many patients to avoid more invasive procedures. The cardiac imaging team works closely with Children’s Diagnostic Imaging and Radiology Division to provide world-class care to patients.

What is an MRI?

MRI (magnetic resonance imaging) is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. MRI of the heart can be used to:
  • Evaluate the heart and blood vessel structure
  • Evaluate heart function and blood flow through vessels
  • Assess blood flow to the heart muscle
  • Evaluate infections
  • Detect tumors
The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. This magnetic field, along with a radiofrequency, alters the natural alignment of hydrogen atoms in the body. Computers are then used to form two-dimensional images of the heart's structure based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use radiation, like x-rays or computed tomography (CT scans).

MRI does not pose any risks unless your child has any kind of implanted metal objects in the body. Be sure to let your child's physician know if your child has any of the following:
  • Implanted pacemaker
  • Implanted medication device, such as an insulin pump
  • Metal clips or pins, or other metal objects in the body
  • Any bullet wounds, particularly if the bullet remains in the body
  • Any metal joint replacements or heart valve replacements
What is the preparation for a MRI?
  • Make sure your child is not wearing any metal jewelry, hair clips, or barrettes, as these will have to be removed prior to the test.
  • If your child's physician schedules a MRI scan and decides to use contrast dye to enhance the pictures, your child may need to be NPO (fasting, nothing by mouth) for several hours prior to the procedure. You will receive instructions about this from your child's physician or another healthcare professional.
  • You will need to let your child's physician know if your child has ever had a reaction to any contrast dye, or if he/she is allergic to iodine or seafood. If your teenage daughter is pregnant or could be pregnant, you should notify the physician prior to the procedure. If your child has any history of kidney problems, you should also let the doctor or healthcare professional know.
  • Children may receive a mild sedative before the procedure to make them feel more comfortable, and to help them to remain still and quiet during the procedure, which may last 60 to 90 minutes.
  • Parents may be able to stay with their child in the MRI room until he/she becomes sleepy.
How is a MRI performed?
  • The MRI scanner is located in a large room. Your child will lie on a narrow table that slides into the hollow tube-shaped scanner.
  • Your child will be connected to equipment to allow for monitoring of heart rate and breathing. If sedation is used, more extensive monitoring will be performed while your child is asleep.
  • The MRI physician and staff will be in an adjacent room where the equipment controls are located. However, they will be able to see your child through a large window and will be monitoring him/her constantly during the procedure. If your child is not sedated, he/she will be able to let the staff know if he/she needs anything during the procedure.
  • The MRI scanning machine makes loud banging or knocking noises when adjustments are being made. Your child will wear a set of headphones to help protect his/her ears from the noise of the scanner and to hear instructions from the MRI staff. Music may be played in the headphones when instructions are not being given.
  • Once the procedure begins, your child will need to remain very still at all times so that movement will not adversely affect the quality of the images. At intervals, he/she will be instructed to hold his/her breath, if possible, for a few seconds. He/she will then be told when to breathe. Your child should not have to hold his/her breath for longer than a few seconds, so this should not be uncomfortable. Young children who cannot remain still for the procedure will be given medication to help them relax or sleep during the MRI scan.
  • If the MRI scan is being done with and without contrast, your child will receive contrast medication through an IV about halfway through the procedure. He/she may feel a warm or flushed sensation just after the dye goes into the vein - this is a normal sensation and it will go away shortly.
  • Once the procedure is finished, the table will slide out of the scanner. If your child received medication for relaxation or sleep, he/she will be monitored until the medication wears off and he/she is awake again. If an IV was inserted, it will be taken out after the procedure is over and your child is awake.
  • The test normally takes approximately 60 to 90 minutes.
What happens after the procedure?
  • Without sedation, your child should be able to resume normal activities immediately, unless your child's physician instructs you otherwise.
  • With sedation, your child may feel groggy, tired, or sleepy for a period of several hours after the procedure. However, the sedation effects should disappear within a day or so.
  • Depending on the results of the MRI, additional tests or procedures may be scheduled, to gather further diagnostic information.
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Cardiac MRI - Departments & Programs - Children's National Medical Center