Myocarditis is an uncommon disorder that is usually caused by viral, bacterial, or fungal infections that reach the heart.

Viral infections:

• Coxsackie
• Cytomegalovirus
• Hepatitis C
• Herpes
• HIV
• Parvovirus

Bacterial infections:

• Chlamydia
• Mycoplasma
• Streptococcus
• Treponema

Fungal infections:

• Aspergillus
• Candida
• Coccidioides
• Cryptococcus
• Histoplasma
• Schistosomiasis

When you have an infection, your immune system produces special cells that release chemicals to fight off disease. If the infection affects your heart, the disease-fighting cells enter the heart. However, the chemicals produced by an immune response can damage the heart muscle. As a result, the heart can become thick, swollen, and weak. This leads to symptoms of heart failure .

Other causes of myocarditis may include:

• Allergic reactions to certain medications or toxins (alcohol, cocaine, certain chemotherapy drugs, heavy metals, and catecholamines)
• Being around certain chemicals
• Certain diseases that cause inflammation throughout the body (rheumatoid arthritis , sarcoidosis )

There may be no symptoms. If symptoms occur, they may include:

• Abnormal heartbeat
• Chest pain that may resemble a heart attack
• Fatigue
• Fever and other signs of infection including headache, muscle aches, sore throat, diarrhea, or rashes
• Joint pain or swelling
• Leg swelling
• Shortness of breath

Other symptoms that may occur with this disease:

• Fainting , often related to irregular heart rhythms
• Low urine output

A physical examination may reveal the following:

• Abnormal heartbeat or heart sounds (murmurs, extra heart sounds)
• Fluid in the lungs
• Rapid heartbeat (tachycardia)
• Swelling (edema) in the legs

Tests used to diagnosis myocarditis include:

• Blood cultures for infection
• Blood tests for antibodies against the heart muscle and the body itself
• Chest x-ray
• Electrocardiogram (ECG)
• Heart muscle biopsy (endomyocardial biopsy)
• Red blood cell count
• Ultrasound of the heart (echocardiogram )
• White blood cell count

Treatment is aimed at the cause of the problem, and may involve:

• Antibiotics
• Anti-inflammatory medicines to reduce swelling
• Diuretics to remove excess water from the body
• Low-salt diet
• Reduced activity

If the heart muscle is very weak, your health care provider will prescribe medicines to treat heart failure. Abnormal heart rhythms may require the use of additional medications, a pacemaker, or an implantable cardioverter-defibrillator. If a blood clot is in the heart chamber, you will also receive blood thinning medicine.

How well you do depends on the cause of the problem and your overall health. The outlook varies. Some people may recover completely. Others may have permanent heart failure.

• Cardiomyopathy
• Heart failure
• Pericarditis

Call your health care provider if you have symptoms of myocarditis, especially after a recent infection.

Seek immediate medical help if you have severe symptoms or have been diagnosed with myocarditis and have increased:

• Chest pain
• Difficulty breathing
• Swelling

Promptly treating conditions that cause myocarditis may reduce the risk.

Liu PP, Schultheiss HP. Myocarditis. In: Libby P, Bonow RO, Mann DL, Zipes DP. Libby: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007;chap 66.