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Myocarditis

Affecting several thousand Americans each year, myocarditis is a disease marked by inflammation of the heart muscle (myocardium). The real numbers are hard to know because myocarditis often produces no symptoms.

A wide range of infections and other problems can lead to myocarditis, which often develops in people who are otherwise healthy. Prevention or prompt treatment of infections is one of the best ways to prevent myocarditis.

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Causes of Myocarditis

Viral infection is the most common cause of myocarditis.

When you have an infection, your body produces cells to fight infection. These cells also release chemicals. If the disease-fighting cells enter your heart, they can release chemicals that can damage your heart muscle. Your heart may become thick, swollen, and weak. Seeking immediate medical care for infections can help prevent complications.

These are some of the types of infections that can cause myocarditis.

Viral infections

Coxsackie B viruses
Epstein-Barr virus (EBV)
Cytomegalovirus (CMV)
Hepatitis C
Herpes
HIV
Parvovirus

Bacterial infections

Chlamydia (a common sexually transmitted disease)
Mycoplasma (bacteria that cause a lung infection)
Streptococcal (strep) bacteria
Staphylococcal (staph) bacteria
Treponema (the cause of syphilis)
Borrelia (the cause of Lyme disease)

Fungal and parasitic infections can also cause myocarditis.

Other causes of myocarditis include certain chemicals or allergic reactions to medications or toxins such as alcohol, drugs, lead, spider bites, wasp stings, or snakebites; or chemotherapy and radiation therapy. Having an autoimmune disease such as lupus or rheumatoid arthritis that causes inflammation throughout your body may also lead to myocarditis.

Signs and Symptoms of Myocarditis

Myocarditis often has no symptoms. In fact, most people recover and never even know they had it.

If you do have symptoms, they may include one or more of these:

Shortness of breath during exercise at first, then at night while lying down
Abnormal heartbeat, which causes fainting in rare cases
Light-headedness
An often sharp or stabbing chest pain or pressure, which may spread to neck and shoulders
Fatigue
Signs of infection, such as fever, muscle aches, sore throat, headache, or diarrhea
Painful joints
Swollen joints, legs, or neck veins
Small amounts of urine

If you have symptoms like these, your doctor will do a physical exam to check for an abnormal or rapid heartbeat, fluid in your lungs, or leg swelling.

To confirm a diagnosis of myocarditis and spot underlying causes, your doctor may order one or more tests such as:

Blood tests to check for infection, antibodies, or blood cell counts
A chest X-ray to produce an image of your heart, lungs, and other chest structures
An electrocardiogram (ECG) to produce a recording of your heart's electrical activity
A heart ultrasound (echocardiogram) to make an image of your heart and its structures

Less often, doctors order cardiac magnetic resonance imaging (MRI) scans or heart muscle biopsies to help confirm a diagnosis.

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