What is myocarditis?

Definition

Myocarditis is an
inflammation of the heart’s muscular wall, the myocardium. Although rare, it can be devastating. Myocarditis can occur with no symptoms and can remain undiagnosed.

Causes

Many cases of myocarditis have no identifiable cause and are called idiopathic myocarditis. When a cause is identified, the myocarditis falls into one of three categories: infectious, toxic, and immune-mediated.

Infectious myocarditis is caused by either a viral
infection from viruses such as measles,
rabies, or human immunodeficiency virus (HIV); a
bacterial
infection from bacteria such as diphtheria or
Mycobacterium; or a fungal infection from
Aspergillus or
Candida.

Toxic myocarditis is caused by drugs such as chemotherapeutic drugs, lithium,
or cocaine; by heavy metals such as copper, iron, or lead; by toxic substances
such as arsenic, carbon monoxide, or other inhalants; and by physical agents such
as electric shock or radiation.

Immune-mediated myocarditis is caused by an allergic reaction to penicillin or streptomycin; by alloantigens, including heart
transplant rejection; and by autoantigens, including Chagas’
disease, scleroderma, or lupus.

Risk Factors

There are no known risk factors for developing myocarditis.

Symptoms

The symptoms of myocarditis vary from person to person depending on the cause and the severity. Furthermore, some people have no symptoms and are thus asymptomatic. The following symptoms may appear slowly or suddenly: flulike complaints, including fever, fatigue, muscle pain, vomiting, diarrhea, and weakness; a rapid heart rate; chest pain; shortness of breath and respiratory distress; and a loss of consciousness. Sudden, intense myocarditis can lead to congestive heart failure and death.

Screening and Diagnosis

The diagnosis of myocarditis is often difficult. There is no specific test for
it. Many other causes of heart problems must be ruled out. To do this, a doctor
will ask the patient about symptoms and medical history and will perform a
physical exam. Tests may include an electrocardiogram (ECG), which records the
heart’s activity by measuring electrical currents through the heart muscle; a
chest X ray, which uses radiation to take pictures of structures inside the body;
a cardiac enzyme blood test (because, in some cases, certain enzymes are
elevated); an echocardiogram, which uses high-frequency sound waves, or
ultrasound, to examine the size, shape, and motion of the heart; a
biopsy (the removal of a sample of heart tissue to test for
infection); and cardiovascular magnetic resonance imaging (the use of
magnetic waves to take pictures of structures inside the body).

Treatment and Therapy

The universally recommended therapy for myocarditis is bed rest, no physical
activity, and supplemental oxygen. Corticosteroids may be given to help
inflammation, and the patient will most likely be admitted to a hospital.

Specific treatment is directed at the underlying cause, if possible. For
instance, if the cause is a bacterial infection, the doctor will prescribe
antibiotics; if the cause is viral, the doctor will
prescribe antiviral agents. Immunosuppressive therapy may be used if the
myocarditis is caused by an autoimmune disorder such as lupus or scleroderma.

If heart failure symptoms are present, the doctor will prescribe medications to
support the function of the heart. These medications include diuretics,
ACE-inhibitors, beta-blockers, and antiarrhythmic agents. Additionally, a
defibrillator, which helps maintain the normal rhythm of the heart, may be
implanted into the patient’s chest. Severe cases may require a cardiac transplant.

Prevention and Outcomes

Myocarditis is difficult to prevent. To help reduce the chance of getting myocarditis, one should reduce exposure to identified causes. Some examples of prevention include practicing good hygiene to avoid the spread of infection (for example, washing one’s hands regularly), always using latex condoms during sexual intercourse, having monogamous sex, and avoiding illegal drugs.

Bibliography

Brady, W. J., et al. “Myocarditis: Emergency Department Recognition and Management. Emergency Medicine Clinics of North America 22, no. 4 (2004): 865-885.

Crawford, Michael, ed. Current Diagnosis and Treatment—Cardiology. 3d ed. New York: McGraw-Hill Medical, 2009.

Feldman, A. M., and D. McNamara. “Myocarditis.” New England Journal of Medicine 343, no. 19 (2000): 1388-1398.

Felker, G. M., et al. “Underlying Causes and Long-Term Survival in Patients with Initially Unexplained Cardiomyopathy.” New England Journal of Medicine 342 (2000): 1077.

Zipes, Douglas P., et al., eds. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia: Saunders/Elsevier, 2008.