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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.


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.


Inflammation of the muscular walls of the heart.


/myo·car·di·tis/ (-kahr-di´tis) inflammation of the muscular walls of the heart.
acute isolated myocarditis  a frequently fatal, idiopathic, acute myocarditis affecting chiefly the interstitial fibrous tissue.
Fiedler's myocarditis  acute isolated myocarditis
giant cell myocarditis  a subtype of acute isolated myocarditis characterized by the presence of multinucleate giant cells and other inflammatory cells, and by ventricular dilatation, mural thrombi, and wide areas of necrosis.
granulomatous myocarditis  giant cell myocarditis, including also granuloma formation.
hypersensitivity myocarditis  that due to allergic reactions caused by hypersensitivity to various agents, particularly sulfonamides, penicillins, and methyldopa.
interstitial myocarditis  that affecting chiefly the interstitial fibrous tissue.


Inflammation of the myocardium.


Etymology: Gk, mys + kardia + itis, inflammation
inflammation of the myocardium. It may be caused by viral, bacterial, or fungal infection; serum sickness; rheumatic fever; or a chemical agent; or it may be a complication of a collagen disease. Myocarditis most frequently occurs in an acute viral form and is self-limited, but it may lead to acute heart failure. Management includes treatment of the cause, analgesia, oxygen, antiinflammatory agents, constant monitoring, and rest to prevent shock or heart failure. See also acute primary myocarditis, acute secondary myocarditis, acute septic myocarditis.


Cardiology Myocardial inflammation Etiology Idiopathic, viral, toxic Complications Dilated cardiomyopathy. See Acute myocarditis, Borderline myocarditis, Fulminant myocarditis, Giant cell myocarditis, Lymphocytic myocarditis.


Inflammation of the muscular walls of the heart.


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.


inflammation of the myocardium, the muscle of the heart, usually the result of viral infection (especially Coxsackie ), sometimes during or after bacterial and other infections. Causes enlargement of the heart, impaired function and sometimes heart failure. It can present with chest pain, breathlessness, lethargy and fatigue and arrhythmias. Diagnosis is based on history, laboratory tests (to identify infective agent and inflammatory markers), ECG and echocardiography. A rare condition, but one of the causes of sudden death during exercise, especially if a sports participant returns to activity before the infection has resolved completely.


inflammation of heart muscle

myocarditis (mīˈ·ō·kar·dīˑ·tis),

n an inflammatory condition of the myocardium due to fungal, viral, or bacterial infection. It can also be related to a collagen disease, serum sickness, chemical agent or rheumatic fever.


Inflammation of the muscular walls of heart.


inflammation of the muscular walls of the heart (the myocardium). The condition may result from bacterial or viral infections or it may be a toxic inflammation caused by drugs or toxins from infectious agents. A striking example is the myocarditis of foot-and-mouth disease. The effect is to reduce cardiac reserve, possibly to the point of precipitating heart failure. Focal lesions may cause cardiac arrhythmia.

fibrotic myocarditis
healed lesion with much myocardium replaced by scar tissue; cardiac function will be severely compromised.
infectious myocarditis
see goose hepatitis.
primary myocarditis
usually the result of a primary viral or protozoal infection of the myocardium.
secondary myocarditis
associated with an infectious or noninfectious systemic disease or associated with another cardiovascular disorder.
References in periodicals archive ?
Acute myocarditis (predominately lymphocytic) causing sudden death without heart failure.
An autopsied case of acute myocarditis with myocardial calcification.
This case illustrates acute myocarditis complicated by ventricular fibrillation but with a clinical presentation mimicking acute lateral myocardial infarction.
The accuracy of DE-MDCT compared with DE-MRI for the diagnosis of acute myocarditis has been assessed in two small series of patients with a significant correlation between both methods (1,2).
As such, DE-MDCT might be considered as a first-line imaging modality in patients with a strong clinical suspicion of acute myocarditis but in which ECG modifications suggest a possible acute myocardial infarction.
Ventricular arrythmias occuring in the setting of acute myocarditis have been described in the literature and myocarditis is one of the leading causes of sudden deaths in chidren and young adults, responsible for 20 to 40% of them (11).
Acute myocarditis is typically sporadic, although clusters have been reported during outbreaks of viral disease (2,3).
For the 2 patients with fatal cases, the primary autopsy diagnosis was acute myocarditis.
Risk factors for patients developing a fulminant course with acute myocarditis.
The fate of acute myocarditis between spontaneous improvement and evolution to dilated cardiomyopathy: a review.
Recently, we demonstrated that CB3 infection increases IL-113 and IL-18 levels in the heart during acute myocarditis through IL-12R[beta]1 and TLR4 signaling (26).

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