Myocarditis is an inflammatory condition involving the myocardium (heart muscle).
Myocarditis is characterized by a variety of symptoms ranging from fatigue, difficult breathing, and rapid heartbeat to sudden death from fatal arrhythmia (abnormal heart rhythm).
Myocarditis may occur following a wide assortment of diseases, including bacterial and viral infections, immune system disorders, and the production of myocardial toxins by the body, as well as chemical and radiation exposure.
In the early 1900s, myocarditis was recognized as the cause of many cases of congestive heart failure, and a regimen of strictly enforced bedrest was prescribed as being the only treatment having beneficial effects. In spite of the multitude of advances in definition, diagnosis and treatment, this may still be the most effective treatment.
The introduction of endomyocardial biopsy (removal of small amounts of heart muscle for microscopic analysis) now allows a histological, rather than clinical diagnosis. Only 30 percent of the patients with clinical symptoms of myocarditis are shown to have unequivocal biopsy diagnosis - the reason for this discrepancy is controversial. Cardiac imaging, in the form of angiography or computerized tomography, seldom helps in making a definitive diagnosis of myocarditis.
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.
In Central and South America, myocarditis is often due to Chagas disease, an infectious illness that is transmitted by insects.
Symptoms of myocarditis vary widely.
In adults, they can sometimes mimic those of a heart attack - mild to severe pain in the center of the chest, which may radiate to the neck, shoulders, and upper arms. In severe cases, symptoms include breathlessness, rapid pulse, and heart arrhythmias.
In infants, symptoms may also include bluish skin, heart murmurs, and a poor appetite.
Myocarditis may be suspected whenever chest pain or arrhythmia symptoms suggestive of congestive heart failure occur during the course of an infectious illness, especially a viral one. It should also be suspected when such symptoms occur in the absence of an obvious diagnosis.
Myocarditis may start as a flu-like illness that lingers longer than the usual several days. If significant muscle damage and weakening of the heart's chambers occur, symptoms of heart failure may develop. A month or two later, the symptoms of flu (weakness and malaise) merge with symptoms of heart failure (fatigue during physical activity and shortness of breath).
If the illness is persistent and progressive, symptoms become disabling enough for the person to consult a physician. By this time, however, the infecting organism usually cannot be detected or cultured from the heart or other places in the body. By the time the patient seeks medical help, all traces of the infecting organism or disease process that may have triggered the condition may be undetectable.
Diagnosis may require blood tests, a chest X-ray, electrocardiogram or radionuclide angiocardiogram, and, in rare cases, biopsy of a tissue sample from the heart muscle.
Mild, viral-related myocarditis in adults cures itself with little or no direct treatment. Similarly, mild cases caused by other types of infection often require only taking antibiotics or other drugs to treat the underlying disease.
More severe myocarditis may cause marked heart arrhythmias and heart failure if inflammation sufficiently damages the heart muscle or myocardium.
In such cases, medications to stabilize heart function may be necessary. These may include vasodilators, digitalis, diuretics, ACE inhibitors, and other drugs. In certain severe types of myocarditis, steroids may be prescribed.
Sometimes even after myocarditis is resolved, the heart muscle remains permanently damaged. If a heart block or marked slowing of the heart rate occurs, a pacemaker may be required. In advanced, severe cases, cardiac transplantation may be the only alternative.
During the acute phase of myocarditis, patient are advised to rest and gradually return to a more active lifestyle once evidence disappears of ongoing inflammation and heart injury.
Many cases of myocarditis cause minimal heart damage. Heart function fully recovers in these mild cases. Occasionally, severe cases of myocarditis also clear up spontaneously and leave little permanent damage. More typically, however, severe inflammation produces chronic, progressive, and irreversible heart damage.