Acute myocarditis

The medical term for the inflammation of the heart muscle is myocarditis. This usually occurs as a result of a viral infection. The inflammation can affect the entire heart muscle or be limited to a specific area of it. 

The symptoms correspondingly differ, ranging from mild discomfort to sudden heart failure or life-threatening cardiac arrhythmias.

Treatment primarily aims to protect the heart against excessive strain. That means taking things easy physically when experiencing acute myocarditis. Medication is also used. 

Sometimes, heart failure remains once the acute inflammation has gone away. In rare cases, the outlook is so severe that mechanical circulatory support (an “artificial heart”) or even a heart transplant becomes necessary.

Acute myocarditis can have many different symptoms and sometimes even be asymptomatic.

Possible symptoms include:

• signs of heart failure such as rapid exhaustion, shortness of breath during exercise or while at rest, swollen legs
• mild heart palpitations through to strong, sometimes life-threatening cardiac arrhythmias
• rapid heartbeat
• fainting
• chest pain
• abnormal sounds when listening to the heart (murmurs)

Myocarditis is particularly suspected if the patient has had symptoms of a viral infection such as a high temperature, exhaustion or joint and muscle pain in the days leading up to the heart problems.

Myocarditis has multiple causes. In about 50 percent of cases, it is impossible to conclusively determine the cause.

There are two basic types of myocarditis: 

• viral: occurs after infection with a pathogen
• non-viral: results from causes that are not linked to a previous infection

The causes of viral myocarditis include:

• infections, especially with human herpesviruses 6 and parvoviruses B19 (fifth disease pathogens) but also with adenoviruses (pathogens of respiratory and intestinal disorders), human immunodeficiency viruses (HIV) or hepatitis C viruses
• bacterial infections such as diphtheria or tuberculosis
• parasites such as trypanosomes or worms
• fungal infections

The causes of non-viral myocarditis include:

• chronic inflammatory conditions where a misguided immune system triggers the problems, such as connective tissue disorders (sarcoidosis and systemic lupus erythematodes), skeletal muscle disorders (poliomyelitis) or joint disorders (rheumatoid arthritis)
• excessive alcohol consumption
• drug use, especially cocaine
• certain medication and vaccinations
• insect or snake bites

It is assumed that the heart muscle of up to 5 percent of all people with an acute viral infection will also become inflamed.

In 2017, the number of new cases worldwide was estimated to be 1.8 million. The prevalence is the same for men and women.

The outlook for acute myocarditis primarily depends on the causes and the severity of the symptoms. In most people who have no or few symptoms, the inflammation in the heart muscle goes away naturally.

Cases of permanent heart failure or cardiac arrhythmias are rare and cases of sudden cardiac death are even rarer. 

People with severe heart failure and persistent heart arrhythmias are at higher risk of dying and sometimes need mechanical circulatory support (an “artificial heart”) or even a heart transplant.

As myocarditis can last for a long time, regular ultrasound examinations of the heart are required. It can sometimes take months or even years to fully recover from severe myocarditis.

Many people with myocarditis report having had an infection one to two weeks previously. In some, a chronic inflammatory condition has recurred.

However, a physical examination and the description of the symptoms are not sufficient to diagnose myocarditis. Doctors will therefore also perform an electrocardiogram (ECG). This shows the rate at which the heart beats and whether it has a regular rhythm.

An ultrasound examination of the heart (echocardiography) helps assess the movements of the heart muscle and heart valves. Certain blood values can also be checked by taking a blood sample. Elevated values indicate myocarditis. In some cases, further examinations such as a chest X-ray, radiological imaging of the vessels or magnetic resonance tomography (MRT) are also required.

The goal of treatment is to prevent excessive strain on the heart. It is therefore important for patients to take things easy physically during an acute phase of myocarditis. Athletes should avoid competing for 3 to 6 months. 

In the case of symptoms of heart failure, doctors prescribe medication that supports the heart with its work. In rare cases, the heart failure is so severe that mechanical circulatory support (an “artificial heart”) or even a heart transplant is required.

In the case of cardiac arrhythmias, medication can be used to normalize the heart rhythm. As even asymptomatic arrhythmias can be life-threatening, temporary monitoring in a hospital may be necessary. 

Abnormal heart wall motion can cause the formation of blood clots in the heart chambers. In such cases, medication that inhibits blood clotting is required. 

It can be necessary to suppress the body’s own immune defenses with medication – for example in the case of certain rare conditions or an autoimmune disease. Medication for combating certain viruses is only sometimes useful. This is because the virus has usually already gone by the time myocarditis is diagnosed. 

People with symptoms of heart failure in particular should attend regular follow-up examinations involving an echocardiogram (ultrasound of the heart).

It is also important to regularly take the medication prescribed to prevent excessive strain on the heart. 

During the accompanying physiotherapy, people with myocarditis receive guidance on breathing therapy and light physical exercise. Most people benefit from a special rehabilitation program. This aims to promote recovery by helping them develop a healthy lifestyle.