Myocarditis is inflammation of the heart muscle. It is most often caused by a virus, but can also be caused by bacteria, a fungus or even certain chemicals. In response to the infection, the body turns against its own heart muscle. It is not known why the viral infection affects the hearts of some people but not of most others. Some cases of myocarditis are very mild and patients recover on their own without the need for any treatment. Other cases can be much more serious and sometimes life threatening. 

In severe cases of myocarditis, the inflammation of the heart muscle can cause serious problems. It can interfere with the muscle’s squeezing ability, and this can decrease the heart’s ability to pump blood effectively. Also, the inflammation can interfere with the heart’s electrical system, which can cause abnormal heart rhythms (arrhythmias).

Symptoms of Myocarditis

Myocarditis is often seen after a typical viral illness. Patients will frequently report being sick with fever, aches, runny nose and or cough a week or two before they started having problems with their heart. This is a normal viral illness many people get. As mentioned above, sometimes that virus will then cause inflammation of the heart, which inadvertently triggers the body to turn against its own heart. 

Once this happens, symptoms of myocarditis include:

• Pallor: The skin may appear more pale than usual because the blood vessels close to the skin surface constrict in order to allow blood to preferentially go to the vital organs.
• Fast heart rate: The heart beats faster in its attempt to deliver more blood to the body.  
• Arrhythmia: The sick heart may create abnormal heart rhythms, some of which may be life threatening.
• Shortness of breath with exertion/fatigue: As the heart’s lower left chamber (left ventricle) fails to pump blood out to the body effectively, proper flow of blood through the other heart chambers and the blood vessels from the lungs to the heart is restricted. One result can be a build-up of fluid in the lungs, which can make oxygenation more difficult. The skin may become cool and wet due to sweating (diaphoretic).
• Poor appetite and failure to grow properly: Because of the extra calories used by the heart and body to struggle to maintain proper blood flow, growth may be affected, particularly in babies.  

Progression and Possible Complications of Myocarditis

If myocarditis is caused by a virus, it may improve on its own. Medications may help the heart undergo this healing process. If the myocarditis improves, the child can lead a normal life thereafter. It is believed that about one-third of patients with myocarditis get better, one-third stay the same with reduced heart function, and the condition severely deteriorates in about one-third of patients. Once the inflammation goes away, the heart muscle may be severely damaged. This can lead to a weakened, enlarged heart. This is called dilated cardiomyopathy. 

Treatments for Myocarditis

The following medications may be prescribed to treat myocarditis:

• Anti-inflammatory agents: In cases of suspected myocarditis, intravenous immunoglobulin (IVIG) - a concentrated preparation of antibodies - is commonly given shortly after the diagnosis is made to try to combat the immune reaction and inflammation. Steroids are sometimes given as well to try to quiet the immune response against the heart. However, these medicines do not always help.
• Diuretics: These are medications that reduce the volume of blood in the body by increasing the need to urinate and eliminate fluids from the body.  With less blood to pump, the burden on the heart is reduced. Diuretics, such as furosemide, are among the medications that help the body rid itself of excess fluids. 
• Beta blockers: These medications are commonly used to reduce blood pressure. However, in the treatment of heart failure, these are used to blunt the body’s complex excessive adrenaline/hormone responses (neurohormonal response) that can actually worsen the heart failure.
• Afterload reducers: These medications allow blood to flow to the body and tissues easier. In oral form, these include ACE inhibitors (the names of these medications usually end in -pril) or angiotensin receptor blockers (ARB). In intravenous form, this may include milrinone.
• Inotropes: These help the heart to contract better. Digoxin is an oral medication that is sometimes used for sick hearts. In cases of severe heart dysfunction, IV (intravenous) medications given by a continuous infusion, such as milrinone or dobutamine, might be used.
• Antiarrhythmics: These medications are used to help control the heart rhythm and to reduce abnormal heartbeats.