Conditions Myocarditis (inflammation of the heart muscle)

The medical term for the inflammation of the heart muscle is myocarditis. Myocarditis can have a range of causes. In most cases, it occurs as a result of a viral infection. However, it may also have non-inflammatory causes, and occur as part of systemic diseases or as a result of taking certain medication/drugs. 

The inflammation can affect the entire heart muscle or be limited to a specific area of it. Accordingly, the symptoms experienced vary widely, from none at all, to mild symptoms, to heart failure, severe cardiac arrhythmias and even sudden cardiac death.

The most important treatment measure is to prevent excessive strain on the heart. That means strictly limiting physical activity when experiencing acute myocarditis. Medication may also be used. 

Inflammation of the heart muscle can lead to heart failure. In certain cases, the heart failure may remain even after the inflammation has healed. In rare cases, the outlook is so severe that mechanical circulatory support (an “artificial heart”) or even a heart transplant becomes necessary.

Acute myocarditis has a very wide range of possible symptoms and can sometimes even be asymptomatic.

Possible symptoms include:

• chest pain
• 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

Myocarditis is particularly likely if the patient has had symptoms of a viral infection in the days leading up to the heart issues. These symptoms include a high temperature, exhaustion, joint and muscle pain, vomiting and diarrhea.

Myocarditis can have many different causes. In around half of all cases, it is impossible to conclusively determine the precise cause. The most common known cause is a viral infection.

Inflammation of the heart muscle can occur following an infection with certain disease-causing microorganisms (pathogens). These pathogens include, for example:

• viruses, such as herpesvirus 6 and parvovirus B19 (pathogens that cause fifth disease), the SARS-CoV‑2 coronavirus, adenoviruses (pathogens that cause respiratory and intestinal diseases), HIV viruses and hepatitis C viruses
• bacteria, such as the pathogens that cause diphtheria or tuberculosis
• parasites, such as trypanosomes or worms
• fungi

In addition, autoimmune diseases can cause inflammation of the heart muscle. In this case, the body’s impaired immune system mistakenly targets its own heart muscle cells. Examples of these autoimmune diseases include:

• connective tissue disorders, such as sarcoidosis and systemic lupus erythematodes
• skeletal muscle disorders, such as poliomyelitis
• joint diseases, such as rheumatoid arthritis

Myocarditis can also be caused by:

• excessive alcohol consumption
• drug use, especially cocaine use
• certain medication or vaccines
• insect or snake bites
• radiation of the chest, for example as part of cancer treatment

It is difficult to determine the prevalence of myocarditis with precision because the inflammation often causes only mild symptoms or none at all. It is estimated that, every year, around 10 in every 100,000 people globally become ill with myocarditis.
On average, most cases affect younger adults between 30 and 45 years of age. Men are more commonly affected than women.

Young children and adolescents are affected to an equal degree. Among young children, the incidence in boys and girls is the same. Children under the age of 2 are also at an increased risk of developing a severe form of myocarditis.

The outlook for myocarditis primarily depends on the causes and the severity of the symptoms. In most people who have few symptoms or none, the inflammation in the heart muscle goes away naturally. In some cases, harmless cardiac arrhythmias may persist.

People with severe heart failure and persistent heart arrhythmias are at an increased risk of dying. For this reason, some patients need mechanical circulatory support (an “artificial heart”) or even a heart transplant.

Myocarditis can be a protracted and chronic disease. Heart failure can also develop following the acute phase of the disease. Regular follow-up examinations of the heart are therefore required. Some people recover quickly from myocarditis. In severe cases, however, it may take months or even years to make a full recovery.

Many people with myocarditis report having had an infection one to two weeks prior to the start of symptoms. In some, a chronic inflammatory condition has recurred.

However, a physical examination and the description of the symptoms are not sufficient to reliably diagnose myocarditis. Doctors therefore conduct additional examinations.

An electrocardiogram ( ECG) shows, for example, the rate at which the heart beats and whether it has a regular rhythm. With myocarditis, it can detect changes including cardiac arrhythmias.

An ultrasound examination of the heart (echocardiography) helps assess the movements of the heart muscle and the function of the heart valves. Testing of a blood sample may also reveal indications of myocarditis. In some cases, further examinations such as a chest X‑ray or radiological imaging of the coronary arteries are also required in order to rule out cardiovascular diseases. Today, magnetic resonance imaging (MRI) is one of the most important diagnostic methods used. It can detect changes in the heart muscle, such as inflammation or scarring, without the need for surgery. Some medical associations now regard MRI as being of equal diagnostic value as taking a sample of tissue (biopsy) from the heart.

Medication is not required to treat all cases of myocarditis. The most important treatment measure is to prevent excessive strain on the heart. It is therefore essential to strictly limit physical activity during the acute phase of myocarditis. Some types of sport must be stopped for up to 6 months. When and to what extent physical activity can be resumed should be discussed with the patient’s doctor.

In the case of symptoms of heart failure, doctors prescribe medication that makes it easier for the heart to do its job. In rare cases, 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 may be used to normalize the heart rhythm. Even arrhythmias that do not initially cause any symptoms can potentially be fatal. Temporary monitoring in hospital may therefore be required. 

Abnormal movement of the heart muscle can cause the formation of blood clots in the heart chambers. These blood clots can block the blood vessels. In such cases, medication that inhibits blood clotting is required. 

It is sometimes necessary to suppress the body’s own immune system with medication – for example, in the case of certain rare conditions or an autoimmune disease. 
Medication that targets viruses is only useful in certain cases.

Targeted treatment of myocarditis is only possible in the case of a small number of specific causes. If the myocarditis was caused by drugs or alcohol, it is particularly important to avoid these substances entirely.

Regular check-ups are important following acute myocarditis because, in up to 20 percent of cases, the disease results in heart failure.

The first check-up should be scheduled within 3 to 6 months of the acute phase, depending on the severity of the disease. As of this point, annual examinations are normally recommended for at least the next four years. However, the progression of the disease and the detected damage to the heart muscle will determine the period for which regular monitoring is required. In some cases, a one-off check-up after a year is sufficient. In others, life-long monitoring will be necessary. This may involve, for example, ECGs, blood tests or ultrasound scans of the heart (echocardiography). 

People who have already had myocarditis once are at an increased risk of developing it again. Long-term medical care is therefore important.