What are cardiac MRI and CT scans?

Both cardiac MRI and cardiac CT scans are used to take images of the heart:

• Cardiac MRI. This uses strong magnets and radio waves but no X-rays. A cardiac MRI scan can show problems with heart structure, blood flow problems, or tissue damage.

• Cardiac CT scan. This uses X-rays and a computer. A cardiac CT scan can show problems with heart structure, especially if there is damage to blood vessels.

Before the MRI or CT scan

You may need to do the following before your child’s cardiac MRI or CT scan:

• Follow any directions your child is given for taking medicines and for not eating or drinking before the test.

• Your child can follow their normal daily routine unless the healthcare provider tells you otherwise.

• Make sure your child removes any makeup. Makeup may contain some metal.

• Remove ear (cochlear) implants.

• Make a list of all known implanted devices and any metal in your child's body. These include shrapnel or bullet fragments. Discuss these with your child's healthcare provider and the MRI technologist. If there is any uncertainty, an X-ray may be taken of the involved body part to be sure.  

• Remove any metal objects from your child, including watches, eyeglasses, hearing aids, jewelry, belts, or clothing with zippers. These things may interfere with the MRI scanner’s magnetic field. Dental braces and fillings aren’t a problem. But in many cases, MRI scans shouldn’t be done on children who have metal implants. 

Tell your child's healthcare provider and the technologist doing the test if your child:

• Has ever had an imaging test, such an MRI or CT with contrast dye

• Is allergic to contrast dye, iodine, shellfish, or any medicines

• Has a serious health problem. This includes diabetes, kidney disease, or a liver transplant. Your child may not be able to have the contrast material used for MRI.

• Is pregnant or may be pregnant, or is breastfeeding

• Has any implanted device or metal clips or pins in their body

 Precautions

MRI uses strong magnets. Metal is affected by magnets and can distort the image. The magnet used in MRI can cause metal objects in your child’s body to move. If your child has a metal implant, they may not be able to have an MRI unless the implant is certified as MRI safe. People with these implants should not have an MRI:

• Certain clips used for brain aneurysms

• Certain metal coils put in blood vessels

• Certain ear (cochlear) implants

• Some defibrillators

• Some pacemakers

Tell your child’s healthcare provider and the technologist doing the scan if your child:

• Gets nervous or scared in small, enclosed spaces (claustrophobic)

• Has a bullet or other metal in their body

• Has braces. In most cases, braces will not prevent your child from having an MRI, but they can affect the quality of face or head images.

• Has had past surgery

• Has implanted nerve stimulators or medicine-infusion ports

• Has metal splinters in their body

• Has tattoos or body piercings. Some tattoo inks contain metal that can become hot during the test.

• Wears a medicated adhesive patch

Follow all other directions given by your child’s healthcare provider.

During the scan

A cardiac MRI scan takes pictures of your child’s heart.

The scan is done by a technologist. It is interpreted by either a radiologist or a cardiologist. A radiologist is a healthcare provider trained to diagnose and treat problems with imaging technology. A cardiologist is a healthcare provider trained to diagnose and treat heart problems. The scan can take place in either a hospital or outpatient imaging center. A cardiac MRI scan lasts about 60 to 90 minutes. A cardiac CT scan lasts about 30 minutes. Here is what you can generally expect during the scan:

• You can stay with your child in the testing room until the scanning begins.

• Your child lies on a table that slides into the scanner.

• Your child must stay still during the scan. Movement affects the quality of the results. If your child moves too much they may even need a repeat scan. To help keep your child still, restraints may be used. Your child may also be given a medicine to make them relax or sleep (sedative). This is done by mouth or through an IV (intravenous) line. Or your child is given medicine that makes them sleep and not feel pain (anesthesia). This is done by face mask or IV. A trained nurse or another healthcare provider (anesthesiologist)  is in charge of this process.

• Contrast dye may be used to improve image results. Your child is given contrast dye through an IV line.

• The technologist will put a coil over the heart during a cardiac MRI scan. The coil sends and receives radio waves and helps improve image results.

• Small, stick-on patches may be put on the chest. 

• The technologist is nearby and views your child through a window at all times.

• If awake, your child can speak to and hear the technologist through a speaker inside the scanner.

• During a cardiac MRI scan, your child will get earplugs to block out the noise from the scanner.

• During a cardiac CT scan, older children may be asked to hold their breath at certain points to improve image results.

After the scan

What to expect after the scan:

• If a sedative or anesthesia was given, your child will be taken to a postanesthesia care unit to be watched as they wake up. It may take 1 to 2 hours for any medicines to wear off.

• Unless told not to, your child can return to a normal routine and diet right away.

• Any contrast dye your child is given should pass through the body in about 24 hours. The healthcare provider may tell you that your child should drink extra water or other fluids during this time.

• The images are looked at by a radiologist and cardiologist. The cardiologist will follow up with you with complete results.

Risks and possible complications include: 

• Allergic reaction to contrast dye, such as hives, itching, or wheezing

• Kidney damage from IV contrast dye used in CT scan (rare)

• Nephrogenic systemic fibrosis. This is a serious illness that has been linked to MRI IV gadolinium contrast material (extremely rare). This condition is linked to those with kidney disease.

• Problems with undetected metal implants or foreign bodies (only with MRI)

• Radiation exposure from X-rays (only with CT scan)

• Reaction to sedative or anesthesia, such as headaches, shivering, and vomiting

How to help your child get ready

You can help your child by preparing in advance. How you do this depends on your child’s needs:

• Explain the test to your child in brief and simple terms. Younger children have shorter attention spans, so do this shortly before the test. Older children can be given more time to understand the test in advance.

• Make sure your child understands which body part or parts will be involved in the test.

• As best you can, describe how the test will feel. An IV may be put into the arm or hand to give medicines or contrast dye. This may cause a brief sting. Your child won’t feel any discomfort once the medicines take effect. If awake, your child may become uncomfortable from lying still.

• Allow your child to ask questions and answer those questions truthfully. Your child may feel nervous or afraid. They may even cry. Let your child know that you’ll be nearby during the test.

• Many hospitals have a child life specialist. This person is specially trained to help children understand what to expect during their time in the hospital. Books, videos, dolls, and toys may be used to help explain the procedure to your child. Ask your child’s healthcare provider about the resources available at your hospital.