What are the other Names for this Condition? (Also known as/Synonyms)

• Granulomatous Myocarditis
• Idiopathic Giant-Cell Myocarditis (IGCM)
• Myocarditis of the Giant Cell type

What is Giant Cell Myocarditis? (Definition/Background Information)

• Giant Cell Myocarditis (GCM) is a heart disorder that is caused by the presence of giant cells within the heart muscles. It is a rare condition that is seen in young and middle-aged adults
• In many cases, Giant Cell Myocarditis is a rapidly-progressing condition leading to congestive heart failure; death is even known to occur within 6 weeks of onset of signs and symptoms
• The exact cause of Giant Cell Myocarditis is unknown, but it may be induced by an abnormal immune system. The identified risk factors for GCM include Crohn’s disease and tumor of the thymus gland
• The condition may cause chest pain, breathing issues, and congestive heart failure. Giant Cell Myocarditis may result in complications that include arrhythmias, heart blocks, or buildup of fluid around the heart (pericardial effusion)
• The diagnosis of Giant Cell Myocarditis may require a thorough physical checkup by the healthcare provider, blood tests, imaging studies of the heart, and an endomyocardial biopsy
• The treatment of Giant Cell Myocarditis includes steroid therapy, management of arrhythmias using anti-arrhythmic medication, immunotherapy, and heart transplantation for severe cases
• In many cases, the prognosis of Giant Cell Myocarditis is guarded despite intensive treatment. A successful heart transplant may prolong survival in the affected individuals; although, the condition is known to recur even in a transplanted heart

Who gets Giant Cell Myocarditis? (Age and Sex Distribution)

• Giant Cell Myocarditis is a very infrequent condition that is mostly observed during young and middle-age (average age 42 years)
• Both males and females are affected and no gender preference is observed
• All races and ethnic groups are at risk and no predilection is noted

What are the Risk Factors for Giant Cell Myocarditis? (Predisposing Factors)

The risk factors for Giant Cell Myocarditis include:

• Presence of thymoma (tumor of the thymus gland in the chest)
• Inflammatory bowel disease including Crohn’s disease

Even though several members of a family may be occasionally affected by myocarditis, a positive family history for this heart condition is not yet reported.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Giant Cell Myocarditis? (Etiology)

The cause of development of Giant Cell Myocarditis is generally not well-defined. Hence, it is also known as Idiopathic Giant-Cell Myocarditis (IGCM).

• It may be caused by abnormalities in the immune system, which is brought about by a variety of unknown triggers
• Some researchers believe that GCM may occur due to certain bacterial infections, including tuberculosis and syphilis, or following other fungal and viral infections

What are the Sign and Symptoms of Giant Cell Myocarditis?

The signs and symptoms of Giant Cell Myocarditis vary from one individual to another; it may be mild in some and severe in others. Following are some of the common signs and symptoms noted:

• Chest pain and discomfort; acute chest pain can mimic heart attacks
• Fatigue
• Decreased ability to exercise, or decreased exercise tolerance
• Palpitations; abnormal heart beats
• Heart rhythm abnormalities (arrhythmias)
• If the individual has congestive heart failure, then it can result in shortness of breath, tiredness, and swelling of the extremities

The signs and symptoms of any underlying condition, if any, may be noted.

How is Giant Cell Myocarditis Diagnosed?

In general, Giant Cell Myocarditis is a cardiac condition that is difficult to be diagnosed. A healthcare provider may use some of the following methods to diagnose GCM:

• Complete evaluation of family (medical) history, along with a thorough physical examination, including examination of the heart
• Blood tests that include:
  • Calcium test and vitamin D blood level test
  • Angiotensin-converting enzyme blood test
  • Erythrocyte sedimentation rate (ESR) test
  • C-reactive protein levels in blood
  • Cardiac enzyme panel test; tests for cardiac enzymes
• Tissue cultures to rule-out infectious diseases
• Imaging studies that include:
  • Chest X-ray
  • Doppler ultrasound: Sound waves are used to measure the speed and direction of blood flow
  • CT scan of the heart
  • Contrast-enhanced MRI scan of heart
  • Positron emission tomography (PET) scan
• Electrocardiogram (ECG): It is used to measure the electrical activity of the heart, in case of arrhythmias
• Scintigraphy using thallium‐201 and gallium‐67
• Endomyocardial biopsy: A tissue biopsy is performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis

A differential diagnosis may be undertaken to eliminate the following heart conditions prior to arriving at a definitive diagnosis of GCM:

• Cardiac sarcoidosis
• Hypersensitivity myocarditis
• Lymphocytic myocarditis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Giant Cell Myocarditis?

Some potential complications of Giant Cell Myocarditis include:

• Abnormal heart rhythms and conduction disorders
• Inflammation of the sac surrounding the heart (called pericarditis) and collection of fluid around the heart (called pericardial effusion)
• Partial or complete heart block due to scarring of heart tissue
• Sudden death
• Recurrence of the condition: In 1 in 4 individuals, GCM can occur in the newly-transplanted heart too. The average duration of recurrence after transplant is about 12 months

How is Giant Cell Myocarditis Treated?

Giant Cell Myocarditis may be treated through the following measures:

• Steroid therapy; prescription of anti-inflammatory drugs
• For those with arrhythmias, anti-arrhythmic medication may be administered
• Immunosuppressive therapy
• Pacemaker and defibrillator implantation
• Pericardiocentesis (removal of fluid from pericardial sac) may be performed in case of pericardial effusion
• Heart transplantation, in case of severe symptoms and complications
• Observation and periodic checkups to monitor the condition is recommended

How can Giant Cell Myocarditis be Prevented?

• Presently, there are no definitive preventative measures available for Giant Cell Myocarditis
• Undertaking prompt and appropriate treatment of any underlying conditions, such as thymoma or inflammatory bowel disorder (IBD), is recommended

What is the Prognosis? (Outcomes/Resolutions)

The prognosis of Giant Cell Myocarditis is typically guarded, since it is a rapidly-progressing heart condition.

• It is reported that over two-thirds of the individuals do not survive beyond 12 months after diagnosis. In some cases, death may occur within 1.5 months of first symptom presentation
• Individuals, who survive the condition may be prone to heart blocks (partial or complete), due to scarring of the heart
• In case a heart transplant is performed, it is noted that 70% of the individuals survive for a period of 5 years following the transplant procedure
• In about 25% of the individuals who undergo heart transplantation, GCM may recur within a time frame of 3 weeks to anywhere up to 9 years after the procedure

Additional and Relevant Useful Information for Giant Cell Myocarditis:

The following article link will help you understand other heart conditions:

http://www.dovemed.com/healthy-living/heart-center/