Giant Cell Myocarditis

What is giant cell myocarditis?

Giant cell myocarditis is a very rare type of heart muscle inflammation. Inflammatory cells come together to form giant cells that attack your heart muscle and cause scarring. This can quickly lead to problems with how well your heart can:

• Pump blood.
• Contract all of its parts at the same time during a heartbeat.
• Allow heartbeat signals to take a normal, uninterrupted route through your heart.

Because giant cell myocarditis is often fatal, many people who have it need a heart transplant.

What is the difference between myocarditis and giant cell myocarditis?

Giant cell myocarditis is a very rare type of myocarditis. People who have GCM can have abnormal heart rhythms like those with other types of myocarditis. Usually, a viral infection causes myocarditis. Researchers are still figuring out what causes giant cell myocarditis.

Who does giant cell myocarditis affect?

Most people who get giant cell myocarditis are young adults or middle-aged people who were healthy before getting GCM. However, it can happen to people in other age groups, regardless of sex.

How common is giant cell myocarditis?

Giant cell myocarditis is very rare. Each year, providers diagnose 0.13 people out of 100,000.

What are the symptoms?

Giant cell myocarditis's early symptoms include:

• Heart palpitations.
• Chest pain.
• Shortness of breath.
• Swollen ankles.
• Extreme tiredness.

Giant cell myocarditis symptoms often develop quickly, with abnormal heart rhythms starting later. More than half of people with giant cell myocarditis have ventricular arrhythmias, which are dangerous heart rhythms that can cause your heart to stop.

With giant cell myocarditis, your heartbeat may be too fast or too slow. That can make you feel lightheaded or pass out.

People with GCM may also have cardiogenic shock.

What causes giant cell myocarditis?

Researchers don’t know the cause of giant cell myocarditis. They’re exploring possible causes, such as infections, an abnormality of your immune system, or something in your genes that makes you more likely to get GCM.

Since 20% of people who get giant cell myocarditis also have autoimmune disorders, those conditions may be another cause or risk factor.

How is giant cell myocarditis diagnosed?

Your healthcare provider will take a sample (biopsy) of your heart tissue to make a giant cell myocarditis diagnosis. They’ll send it to their lab, where an expert cardiac pathologist will analyze the sample to make a diagnosis. Having an expert analyze the sample is important because the biopsy results for giant cell myocarditis can be similar to other diseases that cause inflammation of the heart muscle like cardiac sarcoidosis. It is important to get an exact diagnosis because it will change your treatment plan.

This biopsy procedure carries some risk, but it’s the only way to be sure you have giant cell myocarditis. Complications of a heart muscle biopsy may include:

• Pericardial effusion.
• Cardiac tamponade.
• A puncture in your ventricle wall (the wall of your heart chamber).

To get the sample, your provider puts a catheter into a blood vessel in your neck or groin and uses imaging to guide the catheter into your heart. A special tool inside the catheter takes a piece of heart tissue.

You may need more than one biopsy because GCM may affect some areas and not others. Imaging (like an MRI of your heart) can help your provider decide where to take a biopsy.

What tests will be done to diagnose giant cell myocarditis?

If your healthcare provider wants to make sure you don’t have a different heart issue, they may order other tests.

Tests may include:

• Electrocardiogram (EKG).
• Echocardiogram.
• Cardiac catheterization.

How is giant cell myocarditis treated?

Your healthcare provider can prescribe drugs that can:

• Reduce inflammation.
• Help keep you from getting abnormal heart rhythms or heart failure.
• Give yourself more time until you need a heart transplant.
• Help you live longer.

Other giant cell myocarditis treatments address heart failure and abnormal heart rhythms. Treatments may include:

• Medicines.
• Catheter ablation.
• Pacemaker.
• Implantable cardioverter defibrillator (ICD).
• Heart transplant.

You may need a left ventricular assist device while waiting for a heart transplant. If you need a heart transplant you'll need to be evaluated and treated at a hospital that has a heart transplant program.

What medications are used?

Giant cell myocarditis treatment includes medicines that suppress your immune system.

These may include:

• Cyclosporine (Gengraf® or Neoral®).
• Corticosteroids like prednisone (Sterapred® of Rayos®).
• Azathioprine (Imuran® or Azasan®).

It’s important to start taking these medicines right away. Without them, you only have about three months between when symptoms start and when you need a transplant or the condition becomes fatal. People who take medicine to suppress their immune system can live an average of 12 months.

Side effects of the treatment

Your side effects may vary, depending on which drug you’re taking.

Side effects may include:

• Muscle pain or weakness.
• Headache.
• High blood sugar.
• Diarrhea.
• Difficulty sleeping.

What can I expect if I have giant cell myocarditis?

If you have giant cell myocarditis, it may lead to heart failure or heart block. When these conditions get worse (in about five months), you may need a heart transplant if you qualify for one. Most people don’t have symptoms after receiving a new heart but have to take many new medicines to support their new heart.

Can you survive giant cell myocarditis?

You can survive giant cell myocarditis longer than in the past, but it’s still a fatal disease without a heart transplant. Throughout most of the 1900s, people lived less than three months with GCM. Today, 90% of people with giant cell myocarditis live at least a year when they get a prompt diagnosis and treatment with medicines that suppress their immune system. Medicines can give you months or years before you need a heart transplant.

Giant cell myocarditis prognosis

About 71% of people (82% in another study) with giant cell myocarditis are alive five years after getting a heart transplant. Ten years after a heart transplant, the giant cell myocarditis survival rate is 68%.

Giant cells can return in 10% to 50% of the people who get a new heart. This can happen anywhere from a few weeks after transplant to nine years later. If this happens, you may need to take steroids for a few months.

How do I take care of myself?

If you have giant cell myocarditis, you shouldn’t take part in competitive sports for at least three to six months. If your GCM is stable, ask your healthcare provider if it’s safe for you to get back to exercising little by little.

When should I see my healthcare provider?

Contact your healthcare provider if you’re having bad side effects from the medicine you’re taking or if you notice worsening symptoms. It’s also important to keep going to scheduled appointments with your provider so they can monitor your condition.

When should I go to the ER?

Call 911 if you’re having chest pain or shortness of breath.

What questions should I ask my doctor?

• How often will I need follow-up appointments with you?
• Is there a support group I can join for this disease?
• Do you think I’ll need a heart transplant?

A note from Cleveland Clinic

Giant cell myocarditis is a disease that has a better outlook than it did in the past. People are living longer with it than ever. Your experience with it depends on how quickly your provider diagnoses you and how quickly you start treatment. Be open to treatments your provider recommends for you, such as medical devices that help your heart keep a normal rhythm.