The myocardium is the muscular wall of the heart, or the heart muscle, which contracts to pump blood out of the heart. After pumping, it relaxes as the heart refills with returning blood. The myocardium’s smooth outer membrane is called epicardium, while its inner lining is endocardium. Myocarditis is an inflammation of the myocardium, or middle lining. When the heart becomes inflamed, it cannot pump as well because of the damage done to its cells and swelling. The heart muscle may damage even more if the body’s immune system sends antibodies to try and fight whatever started the inflammation. Sometimes these antibodies attack the tissues of heart instead the cause of myocarditis. If too many heart muscle cells are damaged, the heart muscle weakens. In some cases, this process happens very quickly and results in heart failure or even sudden death. More often, the heart tries to heal itself; the heart muscle heals by changing the damaged or dead heart muscle cells into scar tissue. Scar tissue is not like heart muscle tissue because it does not contract and it cannot help the heart pump blood. If enough scar tissue forms in the heart, it can ultimately lead to congestive heart failure or dilated cardiomyopathy as a consequence of myocarditis.
What causes myocarditis?
- A virus causes one common form of myocarditis, which often occurs after a viral infection of the nose and throat. This myocarditis type often goes away on it own after it runs its course. Although many different viruses can cause myocarditis, coxsackie virus B is the most common in the United States.
- Other viruses that can cause myocarditis include echovirus, influenza, Epstein-Barr, rubella, chickenpox, mumps and hepatitis.
- HIV infection is also a common cause of myocarditis, because about 10% of people with HIV develop this disease. This might occur because HIV directly invades the heart muscle or because the patient's weakened immune system makes the heart muscle more susceptible to attack by other infections.
- Albeit rarely, bacteria can cause myocarditis as a complication of endocarditis, an infection of the heart valves and the lining inside the heart’s chambers. Some common bacteria responsible for myocarditis include Staphylococcus aureus, enterococci and Corynebacterium diphtheriae. In fact, about 25% of people with diphtheria, a toxin produced by C. diphtheriae bacteria, experience a form of myocarditis that leads to a flabby, stretched-out heart muscle. Because the flabby, enlarged heart cannot pump blood efficiently, severe congestive heart failure may develop within the first week of this illness.
- "Chagas" disease is an infection caused by the protozoan Trypanosoma cruzi, transmitted by insect bite. In the United States, myocarditis caused by Chagas’ disease is most common among travelers from Central and South America. In up to one-third of people with Chagas' disease, a form of chronic myocarditis develops many years after the first infection ends. This chronic myocarditis leads to a significant destruction of the heart muscle, with progressive heart failure as a serious consequence.
- Lyme myocarditis can also occur due to Lyme’s disease, an infection with tick-borne bacterium Borrelia burgdorferi. This disease causes myocarditis or other heart problems in about 10% of patients.
- Giant cell myocarditis is a rare form of myocarditis. It takes its name from large, abnormal giant cells found when a piece of the affected heart muscle is examined under a microscope. Giant cell myocarditis is most common among people who have thymoma, which is a growth of the thymus gland. This is a collection of immune-system tissues below the top of the breastbone.
- Other agents are also able to provoke myocarditis, such as alcohol, radiation, chemicals, and drugs, including doxorubicin, cyclophosphamide, emetine, chloroquine and sulfonamides. A recent study also showed that severe emotional stress could produce heart failure that starts abruptly, with evidence of inflammation of heart muscle as well.
Symptoms of myocarditis
The symptoms of myocarditis depend on the cause and severity because some people do not have any symptoms, and their only sign of heart inflammation is a temporary abnormal result on an electrocardiogram. In the same time, other people who developed myocarditis experience fever, chest pain, cardiac arrhythmias, sudden loss of consciousness, or signs of heart failure such as shortness of breath and leg swelling.
Other symptoms are:
- chest pain that may resemble a heart attack
- joint pain or swelling
- abnormal heartbeat
- fatigue
- shortness of breath
- leg swelling
- inability to lay flat
- low urine output
Other symptoms consistent with a viral infection are headache, muscle aches, diarrhea, sore throat, or rashes.
The doctor will suspect myocarditis based on medical history and symptoms. To confirm the diagnosis, your doctor will examine you, and pay special attention to your heart. This exam must follow specific procedures such as ECG, a chest X-ray, and blood tests. In people with signs of more severe heart damage, an echocardiogram or other specialized heart tests may be necessary. This might help your doctor in checking for abnormalities in heart size and function. In some patients, blood tests check whether myocarditis relates to Epstein-Barr virus, hepatitis viruses, HIV, or another virus. Some medical centers can also isolate certain types of viruses from the material taken of patient’s samples. Most commonly, those are samples of stool, throat washings or other body fluids. Myocarditis is hard to diagnose because it can resemble many other similar diseases. Your doctor may suspect that you have myocarditis if your symptoms have appeared within six months of having an infection. A number of tests may help your doctor confirm the diagnosis. With a stethoscope, doctors can listen for a rapid heartbeat or tachycardia, while blood tests check for recent infection or signs of inflammation in the body. A chest x-ray can show the doctors if there is a buildup of fluid in the lungs, called pulmonary edema, which is one of the signs of heart failure. Electrocardiography can help the doctors learn more about your heart rhythm and the size and function of the chambers of the heart. Echocardiography helps your doctor see heart wall motion and overall heart size. Beside these diagnostic methods, there is procedure were a doctor removes a tiny sample of the heart muscle, using a special device called a bioptome. This procedure is called endomyocardial biopsy where the sample undergoes testing for signs of infection.
Myocarditis prevention
You can avoid many cases of myocarditis caused by infections by practicing good hygiene, especially washing your hands often. It is easy to prevent diphtheria myocarditis by undergoing diphtheria immunization. You know all about HIV prevention, so just follow safe sex practices and avoid intravenous drug use. Myocarditis caused by insect-borne Chagas' disease can be prevented by using effective insecticides in Latin American countries where the illness is common. Prompt treatment of diseases that can lead to myocarditis may reduce the risk of developing this condition.
Myocarditis treatment
Treatment of myocarditis depends on the cause and severity you experience. For example, people with only mild viral myocarditis may rest at home. They will be adviced not to smoke or drink, and they will need to limit strenuous activities until an ECG test gives a normal result. People with myocarditis that causes heart failure or cardiac arrhythmias will need hospital treatment. There they will receive oxygen, medication, or a pacemaker to treat or prevent cardiac arrhythmias. Medications including diuretics, digoxin and vasodilators are successful in treating heart failure. Non-steroidal anti-inflammatory drugs are something your doctor might use to relieve pain. Anticoagulants successfully prevent blood clots. Antibiotics, usually given intravenously, are a valuable aid in bacterial myocarditis or Lyme disease treatment. Diphtheria antitoxin and antibiotics should be the therapy of the choice to treat diphtheria myocarditis. Glucocorticoid medication is therapy used to treat giant cell myocarditis.
Other patients with more damage may need to limit some of their activities and take many medicines for the rest of their lives, and live with myocarditis consequences. For patients who have suffered severe damage to the heart, a heart transplant might be the only choice left.
You must call your doctor immediately if you have moderate or severe chest pain, even if you think that you are too young to be having heart problems. Once you report myocarditis in an early stage, it could be easier to treat and achieve better results. People of any age can get the chest pain of myocarditis, with or without other symptoms, so watch for anything you could think is similar to myocarditis. In most people with uncomplicated viral myocarditis, the illness goes away on its own, but you might need some treatment to heal your heart completely and prevent permanent damage.