Myocarditis (inflammation of the heart muscle)

Myocarditis is an inflammation of the heart muscle. If not only the heart muscle (myocardium) itself is affected, but also the pericardium, this is called perimyocarditis.

When inflammation occurs, the heart's ability to contract is impaired, leading to a drop in performance or even heart failure - this is a pathological inability of the heart to pump blood around the body without a particular increase in pressure in the atria. Myocarditis can be the cause of sudden cardiac death.

Myocarditis is usually triggered by a bacterial or viral infection. In Europe and the USA, infections with enteroviruses such as the Coxsackie B viruses are the cause in over 50% of cases. In some cases, myocarditis caused by viruses such as adenoviruses, influenza viruses or mumps viruses can also be detected after influenza infections or gastrointestinal flu.

Bacterial pathogens include Corynebacterium diphtheriae (diphtheria), Mycobacterium tuberculosis (tuberculosis), and pneumococci, but these rarely cause myocarditis in healthy patients with normal immune systems.

Rarely, myocarditis can also be caused by infections with fungi, unicellular organisms (such as toxoplasmosis) or parasites (echinococcosis, trichinosis).

In addition, there are also myocardial inflammations that are not triggered by infections but, for example, by radiation therapies, autoimmune diseases, medications or drug abuse (for example, cocaine).

It is also possible for pericarditis (inflammation of the pericardium) to spread to the heart muscle, resulting in myocarditis.

The severity of symptoms in myocarditis can vary greatly from case to case and ranges from asymptomatic inflammation to severe, even fatal courses. In the initial phase, patients often experience non-specific symptoms such as fatigue, a general feeling of exhaustion, fever and aching limbs. Occasionally, patients also experience chest pain and palpitations. As the heart no longer pumps normally, this can lead to oedema (water retention) in the lungs or legs. In more severe cases, even the slightest physical exertion can cause severe shortness of breath.

If myocarditis is caused by a viral infection, the symptoms often appear shortly after a bout of flu or diarrhoea.

First of all, the attending physician takes a medical history (medical interview), whereby symptoms such as shortness of breath or oedema as well as the fact whether the complaints were preceded by an influenza infection or a diarrhoeal illness can already provide initial indications in the direction of myocarditis.

Subsequently, the suspicion can be confirmed by the following examination methods:

• Blood test: the blood is examined for the presence of antibodies against certain viruses or bacteria that can trigger myocarditis.
• X-ray: Changes in the size of the heart caused by the disease are visible on the X-ray.
• Echocardiography: A cardiac ultrasound can detect any enlargement of the heart cavities or an accumulation of fluid between the heart muscle and the pericardium (known as pericardial effusion).
• Electrocardiogram: An ECG can also provide evidence of myocarditis.
• Magnetic resonance imaging: MRI can be used to distinguish inflamed from healthy heart tissue.
• Biopsy: This involves using a cardiac catheter to remove tissue from the heart muscle and examine it for possible causes of the disease.

Since myocarditis often heals spontaneously, but can also lead to cardiac death within a very short time, it is particularly important to maintain strict physical rest.

If the myocarditis is due to a bacterial infection, it can usually be treated with antibiotics.

In the case of a viral infection, there are no special medications; the only measures that can be taken are those that generally support the course of the disease or alleviate the symptoms:

• Alleviation of pain through painkiller therapy.
• In the case of heart failure, taking diuretics (diuretic medication), beta-blockers and ACE inhibitors.
• Taking medication for cardiac arrhythmias
• In the case of a large pericardial effusion, puncture and aspiration of the accumulated fluid.

In exceptional cases, such as autoimmune diseases, where the body's own defences are directed against the heart muscle tissue, immunosuppressive therapy may be helpful.

If the heart's function is severely and irreversibly damaged by the inflammation, the last option is heart transplantation.

Under medical treatment, the prognosis of myocarditis is usually quite good, so that the inflammation usually heals without permanent damage. There is a possibility that scars remain in the heart tissue, which hardly affect the function of the heart. In more severe cases, the disease can lead to acute heart failure (cardiac insufficiency) or cardiac arrhythmias.

However, it is possible for myocarditis to become chronic, which can lead to a so-called dilated cardiomyopathy of the heart. In this case, there is a pathological enlargement of the heart muscle with a simultaneous decrease in contractile force, which can lead to heart failure. As a result, the body is no longer supplied with sufficient blood, which means that those affected are no longer able to cope with physical strain and already experience shortness of breath during everyday activities such as climbing stairs.

Since myocarditis often develops after a flu-like infection, it is important to take care of the body during colds and to heal properly. Physical exertion and sport should be avoided.

A vaccination against diphtheria offers reliable protection against the variant of myocarditis that is triggered by the corynebacterium diphtheriae.