Myocarditis

Definition

Myocarditis is an inflammatory disease of the heart muscle (myocardium) that can result from a variety of causes. While most cases are produced by a viral infection, an inflammation of the heart muscle may also be instigated by toxins, drugs, and hypersensitive immune reactions. Myocarditis is a rare but serious condition that affects both males and females of any age.

Description

Most cases of myocarditis in the United States originate from a virus, and the disease may remain undiagnosed by doctors due to its general lack of initial symptoms. The disease may also present itself as an acute, catastrophic illness that requires immediate treatment. Although the inflammation or degeneration of the heart muscle that myocarditis causes may be fatal, this disease often goes undetected. It may also disguise itself as ischemic, valvular, or hypertensive heart disease.

An inflammation of the heart muscle may occur as an isolated disorder or be the dominating feature of a systemic disease (one that affects the whole body, like systemic lupus erythematosus ).

Causes and symptoms

While there are several contributing factors that may lead to myocarditis, the primary cause is viral. Myocarditis usually results from the Coxsackie B virus, and may also result from measles, influenza, chicken pox, hepatitis virus, or the adenovirus in children. If an acute onset of severe myocarditis occurs, a patient may display the following symptoms:

• Rhythm disturbances of the heart
• Rapid heartbeat (Ventricular tachycardia )
• Left or right ventricular enlargement
• Shortness of breath (Dyspnea)
• Pulmonary edema (the accumulation of fluid in the lungs due to left-sided heart failure )
• Swollen legs.

Additional causes of myocarditis include:

• Bacterial infections, such as tetanus, gonorrhea, or tuberculosis
• Parasite infections, such as Chagas' disease (which is caused by an insect-borne protozoan most commonly seen in Central and South America)
• Rheumatic fever
• Surgery on the heart
• Radiation therapy for cancer that is localized in the chest, such as breast or lung cancer
• Certain medications.

As of 1996, research has shown that illegal drugs and toxic substances may also produce acute or chronic injury to the myocardium. These studies also indicate an increase in the incidence of toxic results from the use of cocaine. This illegal drug causes coronary artery spasm, myocardial infarction (heart attack ), and arrhythmias, as well as myocarditis.

Further studies conducted in 1996 indicate that malnutrition encourages the Coxsackie B virus to flourish, leading to the potential development of myocarditis. Human immunodeficiency virus (HIV) is also now recognized as a cause of myocarditis, though its prevalence is not known.

Symptoms of myocarditis may start as fatigue, shortness of breath, fever and aching of the joints, all characteristic of a flu-like illness. In contrast to this type of mild appearance, myocarditis may also appear suddenly in the form of heart failure, or sudden cardiac death without any prior symptoms. If an inflammation of the heart muscle leads to congestive heart failure, symptoms such as swollen feet and ankles, distended neck veins, a rapid heartbeat, and difficulty breathing while reclining may all appear.

Diagnosis

The best way to diagnose myocarditis may be through a person's observation of his or her own symptoms, followed by a thorough medical history and physical exam conducted by a doctor. Further tests usually include laboratory blood studies and echocardiography. An electrocardiogram (ECG) is also routinely used due to its ability to detect a mild case of the disease. Cardiac catheterization and angiography are additional diagnostic tests used to determine the presence of myocarditis, or to rule out other possible heart diseases that may lead to heart failure.

Another measure used to diagnosis myocarditis is the endomyocardial biopsy procedure. This invasive catheterization procedure examines a biopsied, or "snipped," piece of the endocardium (the lining membrane of the inner surface of the heart). The tissue sample is examined to verify the presence of the disease, as well as to try to determine the infective cause. An approach used only with a patient's consent, this procedure may also confirm acute myocarditis, allowing close monitoring of potential congestive heart failure.

Treatment

While myocarditis is a serious condition, there is no medical treatment necessary if it results from a general viral infection. The only steps to recovery include rest and avoidance of physical exertion. Adequate rest becomes more important to recovery if the case is severe myocarditis with signs of dilated cardiomyopathy (disease of the heart muscles). In this case, medical treatment for congestive heart failure may include the following medications: angiotensin converting enzyme (ACE) inhibitors, diuretics to reduce fluid retention, digitalis to stimulate a stronger heartbeat, and low-dose beta-blockers.

If myocarditis is caused by a bacterial infection, the disease is treated with antibiotics to fight the infection. If severe rhythm disturbances are involved, cardiac assist devices, an "artificial heart," or heart transplantation may be the only option for complete recovery.

Prognosis

The outlook for a diagnosed case of myocarditis caused by a viral infection is excellent, with many cases healing themselves spontaneously. Severe or acute myocarditis may be controlled with medication to prevent heart failure. Because this disease may be mild or may be extreme and cause serious arrhythmias, the prognosis varies. Cases of myocarditis may vary from complete healing (with or without significant scarring), to severe congestive heart failure leading to death or requiring a heart transplant.

Inflammation of the myocardium may also cause acute pericarditis (inflammation of the outer lining of the heart). Due to the potential effects of the disease, including sudden death, it is imperative that proper medical attention is obtained.

Prevention

Although myocarditis is an unpredictable disease, the following measures may help prevent its onset. Individuals should:

• Take extra measures to avoid infections, and obtain appropriate treatment for infections.
• Limit alcohol consumption to no more than one or two drinks a day, if any.
• Maintain current immunizations against diphtheria, tetanus, measles, rubella, and polio.
• Avoid anything that may cause the abnormal heart to work too hard, including salt and vigorous exercise.

Resources

ORGANIZATIONS

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. 〈http://www.americanheart.org〉.

National Heart, Lung and Blood Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 251-1222. 〈http://www.nhlbi.nih.gov〉.

KEY TERMS

Adenovirus— One type of virus that can cause upper respiratory tract infections.

Angiography— A procedure which uses x ray after injecting a radiopaque substance to examine the blood vessels and lymphatics.

Arrhythmia— An irregular heartbeat or action.

Cardiac catheterization— A diagnostic procedure that gives a comprehensive examination of how the heart and its blood vessels function; performed by inserting one or more catheters through a peripheral blood vessel in the arm or leg.

Coxsackie B virus— A mild virus belonging to a group of viruses (coxsackievirus) that may produce a variety of illnesses, including myocarditis.

Echocardiography— A noninvasive diagnostic procedure that uses ultrasound to examine internal cardiac structures.

Electrocardiogram— A record of the electrical activity of the heart, with each wave being labeled as P, Q, R, S, and T waves. Often used in the diagnosis of cases of abnormal cardiac rhythm and myocardial damage.

Hypertensive heart disease— High blood pressure resulting in a disease of the heart.

Ischemic heart disease— Insufficient blood supply to the heart muscle (myocardium).

Valvular heart disease— A disease of any one of the four valves that controls blood flow into, through, and out of the heart.

Ventricular tachycardia— An abnormally rapid heartbeat. It includes a series of at least three beats arising from a ventricular area at a rate of more than 100 beats per minute, usually ranging from 150-200 beats per minute.

myocarditis (my-oh-kar-dy-tis) n. acute or chronic inflammation of the heart muscle. It may be seen alone or as part of endomyocarditis.