Definition of Myocarditis:

Myocarditis is inflammation of the heart muscle.

See also: Pediatric myocarditis

Causes, incidence, and risk factors:

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)

Symptoms:

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

Signs and tests:

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:

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.

Expectations (prognosis):

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.

Complications:

• Cardiomyopathy
• Heart failure
• Pericarditis

Calling your health care provider:

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

Prevention:

Promptly treating conditions that cause myocarditis may reduce the risk.