The signs and symptoms of myocarditis vary, depending on the cause and the severity of the disease. The most common signs and symptoms include:

• Chest pain that may feel like a heart attack or angina
• A rapid or abnormal heartbeat (arrhythmia)
• Shortness of breath, at rest or during physical activity
• Fluid retention with swelling of your legs, ankles and feet
• Fatigue

Less-common signs and symptoms include:

• Fainting or a sudden loss of consciousness
• Other symptoms you'd have with a viral infection, such as a headache, body aches, joint pain, fever, a sore throat or diarrhea

Sometimes, people with myocarditis will also develop pericarditis, which is an inflammation of the membrane covering the heart (pericardium). Pericarditis may cause sharp pains over the center of your chest.

In mild cases, myocarditis may have no noticeable symptoms. You may feel ill and have general symptoms of a viral infection and never realize your heart is affected. Some people may never seek medical care and may recover without ever knowing they had myocarditis.

Myocarditis in children
When children develop myocarditis, they may experience these signs and symptoms:

• Fever
• Loss of appetite
• Breathing difficulties
• Bluish or grayish discoloration of the skin

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Years ago, rheumatic fever was a common cause of myocarditis. But today there are usually other causes of myocarditis. Most often it develops due to an infection caused by:

• Viruses. The virus most often associated with myocarditis is coxsackievirus B, which can cause symptoms similar to a mild case of flu. But the viruses that cause common cold (adenovirus) and flu, a rash called "fifth disease" (parvovirus B19), gastrointestinal infections (echovirus), mononucleosis (Epstein-Barr virus) and measles (rubella) are also causes of myocarditis. HIV, the virus that causes AIDS, can directly infiltrate the heart muscle.
• Bacteria. These include Staphylococcus aureus, which can also cause an infection of the heart valves called endocarditis, and a tick-borne bacterium that is responsible for Lyme disease. Myocarditis also occurs in more than one-fourth of all people with the bacterial infection diphtheria.
• Parasites. Among these are such parasites as Trypanosoma cruzi and toxoplasma, including some that are transmitted by insects and can cause a condition called Chagas' disease. This disease is much more prevalent in Central and South America than in the United States, but it can occur in travelers and in immigrants from that part of the world. Chagas' disease is the most common global cause of congestive heart failure.
• Fungi and mold. Some yeast infections (such as candida), molds (such as aspergillus) and other fungi (such as histoplasma, often found in bird droppings) are rare causes of myocarditis.

Myocarditis also sometimes occurs if you're exposed to:

• Certain chemicals. These may include substances such as arsenic and hydrocarbons.
• Medications that may cause an allergic or toxic reaction. These include antibiotics, such as penicillin and sulfonamide drugs, as well as some illegal substances, such as cocaine.
• Other diseases. These include lupus, connective tissue disorders, inflammation of blood vessels (vasculitis), and rare inflammatory conditions, such as Wegener's granulomatosis.

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Call your doctor if you have any of the symptoms of myocarditis, particularly chest pain and shortness of breath. If you've had an infection that sometimes leads to myocarditis, be alert for the symptoms of myocarditis and let your doctor know if they occur. When the symptoms are severe, go to the emergency room or call for emergency medical personnel.

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Your doctor may think you have myocarditis if you've recently had a viral or other type of infection and then developed symptoms that suggest a swollen heart muscle.

Your doctor may also order one or more tests in addition to asking you questions and examining you to make a diagnosis of myocarditis and determine the severity of your condition, including:

• Electrocardiogram (ECG). This noninvasive test evaluates your heart's electrical patterns and can detect abnormal rhythms, as well as a weakened or damaged heart muscle.
• Chest X-ray. An X-ray of your chest will image your heart, showing its size, shape and structure. An X-ray of your lungs can indicate whether there's a buildup of fluid in your lungs, which may mean your heart isn't pumping efficiently.
• Echocardiogram. Sound waves, or ultrasound, can create moving images of the beating heart. An echocardiogram may detect enlargement of your heart, poor pumping function, valve problems or fluid around your heart.
• Blood tests. These tests measure white and red blood cell counts, as well as levels of certain enzymes that indicate damage to your heart muscle. Blood tests can also detect antibodies against viruses and other organisms that may mean you have a myocarditis-related infection.
• Cardiac catheterization. In this test, a small tube (catheter) is inserted into a vein in your leg or neck, and then is threaded into your heart. A special instrument can remove a tiny sample of heart muscle tissue (biopsy) for analysis in the laboratory to see if there are signs of inflammation or infection.

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When myocarditis is severe, it can permanently damage your heart muscle. As its pumping action weakens, strain is put on your heart, causing heart failure. Your heart becomes unable to pump efficiently enough to supply your body with the oxygen-rich blood it needs. A failing heart can also cause blood clots to form, leading to a stroke or heart attack.

People with myocarditis may develop heart arrhythmias, which, in severe cases, can cause sudden death. In very severe cases, myocarditis-related heart failure requires a heart transplant.

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In many cases, the swelling that causes myocarditis improves, either on its own or with treatment, leading to a complete recovery. Treatment of myocarditis focuses on the underlying cause, such as the particular infection that may have caused your heart inflammation.

There's no specific treatment for coxsackievirus B — the most common type of virus that causes myocarditis — other than treatment to relieve pain and other symptoms.

Treating mild cases
In mild cases, your doctor may tell you to rest and prescribe medications to help your body fight off the infection causing myocarditis while your heart recovers. If bacteria are causing the infection, your doctor will prescribe antibiotics. Certain rare types of viral myocarditis, such as giant cell and eosinophilic myocarditis, respond to corticosteroids or other medications to suppress the immune system. In some cases caused by chronic illnesses, such as lupus, the treatment is directed at the underlying disease.

Once your heart inflammation has improved, you can gradually resume a more active lifestyle. In the meantime, your doctor may recommend that you limit the amount of salt in your diet, and avoid alcohol, cigarettes and vigorous exercise. Taking these steps can reduce the workload on your heart.

Drugs to help your heart
If you have rapid or irregular heartbeats as a symptom, your doctor may hospitalize you. You'll receive drugs to regulate your heartbeat. If your heart is weak, your doctor may prescribe medications to strengthen its pumping ability, reduce your heart's workload or help you eliminate excess fluid. These medications may include:

• Angiotensin-converting enzyme (ACE) inhibitors, such as enalapril (Vasotec), captopril (Capoten), lisinopril (Zestril, Prinivil) and ramipril (Altace), which relax the blood vessels in your heart and help blood flow more easily
• Beta blockers such as metoprolol (Toprol-XL) and carvedilol (Coreg), which work in multiple ways to treat heart failure and help control irregular or fast heart rhythms
• Diuretics, such as furosemide (Lasix), which relieve sodium and fluid retention
• Digoxin (Digitek, Lanoxin), which increases the strength of your heart muscle contractions and tends to slow the heartbeat

Treating severe cases
In some severe cases of myocarditis, aggressive treatment may be necessary, such as:

• Intravenous (IV) medications to improve the heart-pumping function
• Placement of a pump in the aorta (intra-aortic balloon pump)
• Use of a temporary artificial heart (assist device)
• Consideration of urgent heart transplantation

Some people may have chronic and irreversible damage to the heart muscle requiring lifelong medications, while other people need medications for just a few months and then recover completely. This variability in the disease makes it difficult for your doctor to predict how you'll do.

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There's no easy prevention for most cases of myocarditis. The risk is rare, but you can take some steps to decrease your risk and the risk to others:

• Avoid people who have a viral or flu-like illness until they have recovered. If you're sick with viral symptoms, try to avoid exposing others.
• Follow good hygiene. Regular hand washing is a good way to help prevent spreading illness.
• Avoid risky behaviors. To minimize your likelihood of contracting an HIV-related myocardial infection, practice safe sex and don't use illicit drugs.
• Dress sensibly for the outdoors. If you spend time in tick-infested areas, wear long-sleeved shirts and long pants to cover as much of your skin as possible. Apply tick or insect repellents that contain DEET.
• Get your immunizations. Stay up to date on the recommended immunizations, including those that protect against rubella and influenza, which can cause myocarditis.

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