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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.


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:
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.


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.


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.


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.


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.



American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300.
National Heart, Lung and Blood Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 251-1222.

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.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


inflammation of the muscular walls of the heart (the myocardium); it may result from bacterial or viral infections or it may be a toxic inflammation caused by drugs or toxins from infectious agents. Other systemic diseases that may be accompanied by myocarditis are trichinosis, serum sickness, rheumatic fever, and collagen diseases. In many cases the etiology is unknown.
Symptoms. Symptoms are flulike; in acute myocarditis there is usually pain in the epigastric region or under the sternum (either ischemic, atypical, or pericardial), as well as dyspnea and cardiac arrhythmias. If the condition persists and becomes chronic, there is pain in the right upper quadrant of the abdomen, owing to hepatic congestion. The latter symptom is a sign of left biventricular failure and often is accompanied by edema and other signs of congestive heart failure.
Treatment (for both symptoms and underlying cause). Acute myocarditis usually subsides when the primary illness improves. It is considered incidental to the systemic disease and, though it may be a serious manifestation of a systemic illness, acute myocarditis often does not require specific treatment. Steroids may be used to reduce the inflammatory process. Antiarrhythmic drugs may be required, as well as therapy to combat congestive heart failure.

If the heart involvement becomes chronic, treatment then must be aimed at management of the chronic heart failure. See also congestive heart failure.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Inflammation of the muscular walls of the heart.
Farlex Partner Medical Dictionary © Farlex 2012


Inflammation of the myocardium.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Cardiology Myocardial inflammation Etiology Idiopathic, viral, toxic Complications Dilated cardiomyopathy. See Acute myocarditis, Borderline myocarditis, Fulminant myocarditis, Giant cell myocarditis, Lymphocytic myocarditis.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


Inflammation of the muscular walls of the heart.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


Inflammation of the heart muscle. This may result from bacterial or viral infection, from RHEUMATIC FEVER, from DIPHTHERIA toxin, from TRYPANOSOMIASIS (CHAGAS' DISEASE) or from nutritional deficiency. See also CARDIOMYOPATHY.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


Inflammation of the muscular walls of heart.
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
[CD4.sup.+] and [CD8.sup.+] T cells have been reported to be involved in the pathogenesis of myocarditis by many authors; however, regulatory T cells (Tregs), a subset of [CD4.sup.+] T cells, have been shown to have protective effects [180, 181].
Despite improving liver indices, our patient developed myocarditis. Therefore, it may be worthwhile to monitor patients for cardiac abnormalities despite signs of improving transaminases.
Myocarditis is the commonest underlying aetiology in patients with suspected acute coronary syndrome with nonobstructive coronary arteries and accounts for up to three quarters of cases in several studies [2, 3].
Influenza myocarditis is traditionally defined by a viral prodrome followed by abrupt decline in cardiac function [10].
Although a broad array of etiologies have been implicated as causes of myocarditis, adenoviruses and enteroviruses, specifically Coxsackie group B serotypes, have traditionally been perceived as the predominant cause.
Our patient was very unusual because cardiac tamponade as a result of lupus-induced pericarditis was her initial presenting symptom of lupus and because her disease remained refractory and even progressed to myocarditis, resulting in severe mitral regurgitation and cardiomyopathy.
'The Myocarditis Foundation's passion and commitment to patients and families affected by cardiovascular diseases is outstanding,' said Sanj K.
Detection of viruses in myocardial tissues by polymerase chain reaction.Evidence of adenovirus as a common cause of myocarditis in children and adults.
C on treatment for a non-ST-elevation myocardial infarction (NSTEMI), which it believed to be most likely due to myocarditis with secondary demand ischemia, and less likely acute coronary syndrome.
Final diagnosis was AMI in 84 patients (39.4%), TTS in 71 patients (33.3%), and myocarditis in 51 patients (23.9%).
Heart failure should raise suspicion of myocarditis and cardiomyopathy.