The myocardium is the muscular wall of the heart, or the heart muscle, which contracts to pump blood out of the heart. After pumping, it relaxes as the heart refills with returning blood. The myocardium’s smooth outer membrane is called epicardium, while its inner lining is endocardium.
Many organisms can infect and injure the heart. Type B, a virus among those that usually infect the gastrointestinal tract, is believed to be the most common offending agent. Many other viruses, such as those of polio, rubella and influenza, have been associated with myocarditis.
It is not clear why the same viruses cause myocarditis in some patients and different diseases - gastroenteritis, pneumonia, or hepatitis, for example - in others.
Myocarditis can occur as a rare complication of bacterial infections, including diphtheria, tuberculosis, typhoid fever, and tetanus. Other infectious organisms, such as rickettsiae and parasites, may also cause inflammation in the heart muscle.
Myocarditis is also caused due to Chagas disease, an infectious illness that is transmitted by insects.
In mild cases, myocarditis may have no noticeable symptoms. You may feel ill and have general symptoms of a viral infection and never realize your heart is affected.
In serious cases, the signs and symptoms of myocarditis vary, depending on the cause of the disease. Common myocarditis symptoms include:
- Chest pain
- A rapid or abnormal heartbeat (arrhythmia)
- Shortness of breath, at rest or during physical activity
- Fluid retention with swelling of your legs, ankles and feet
- Other signs and symptoms you'd have with a viral infection, such as a headache, body aches, joint pain, fever, a sore throat or diarrhea
- Breathing difficulties
- Rapid breathing
- Bluish or grayish discoloration of the skin
The best way to diagnose myocarditis may be through a person's observation of his or her own symptoms, followed by a thorough medical history and physical exam conducted by a doctor. Further tests usually include laboratory blood studies and echocardiography. An electrocardiogram (ECG) is also routinely used due to its ability to detect a mild case of the disease. Cardiac catheterization and angiography are additional diagnostic tests used to determine the presence of myocarditis, or to rule out other possible heart diseases that may lead to heart failure.
Another measure used to diagnosis myocarditis is the endomyocardial biopsy procedure. This invasive catheterization procedure examines a biopsied, or "snipped," piece of the endocardium (the lining membrane of the inner surface of the heart). The tissue sample is examined to verify the presence of the disease, as well as to try to determine the infective cause. An approach used only with a patient's consent, this procedure may also confirm acute myocarditis, allowing close monitoring of potential congestive heart failure.
Treatment of myocarditis depends on the cause and severity. For example, people with only mild viral myocarditis may be allowed to rest at home. They will be advised not to smoke or to drink alcohol, and they will need to limit strenuous activities until an EKG test is normal.
People with myocarditis that causes heart failure or cardiac arrhythmias will be treated in a hospital. There they will receive one or more of the following:
- Medication or a pacemaker to treat or prevent cardiac arrhythmias
- Medication, including diuretics and vasodilators, to treat heart failure
- Nonsteroidal anti-inflammatory drugs (NSAIDs) to relieve pain
- Anticoagulants to prevent blood clots
- Antibiotics to treat bacterial myocarditis or Lyme disease
- Diphtheria antitoxin and antibiotics to treat diphtheria myocarditis
- Glucocorticoid medication to treat autoimmune diseases and sarcoidosis.