Myocarditis is an inflammation of the cardiac muscle tissue. In Western industrial countries, viruses are among the main cause of this disease. Myocarditis can occur at any age. In this context, children below the age of two frequently suffer from severe disease courses involving acute cardiac insufficiency. Likewise, their risk of dying of the disease is significantly higher than that of adult patients. For this risk to be kept down, children and adolescents rely on age-appropriate diagnostics that ensure the option of timely intensive medical intervention up to heart transplantation.

In myocarditis, lymphocytes accumulate in the tissue. They are components of white blood cells and invade the tissue like a growing army with the aim of fighting off the disease agents. Such an “infiltration” of the cardiac muscle tissue by an increased number of these defense cells accordingly suggests myocarditis, that is, an inflammation of the cardiac muscle. Taking and examining tissue samples from the cardiac muscle, also referred to as endomyocardial biopsy (EMB), is therefore considered to be the gold standard for diagnosing myocarditis in children and adults.

MYKKE Register Provides Diagnostic Basis

In order to be able to detect a critically increased amount and activity of lymphocytes by means of an EMB, physicians need reliable reference values from people without the disease. However, the reference values for these lymphocytic cell infiltration specified by the criteria of the World Health Organization and the International Society and Federation of Cardiology, WHO/ISFC criteria in short, are based on analyses of the cardiac muscle tissue or myocardium, respectively, of adults. The MYKKE Register for the first time has succeeded in collecting a sufficient amount of tissue samples from young patients that facilitate an assessment of the inflammation in this particularly affected young age group.

For this purpose, scientists analyzed the endomyocardial tissue of 62 children with congenital heart disease who were below the age of four. The tissue had been taken as a matter of routine during required open heart surgery. Mostly, it was taken from the right ventricle. This happened under the precondition that the patients had no history of infections or myocarditis whatsoever. “We examined their myocardial tissue with respect to the amount of immune defense cells actively involved in the immune defense. These include CD3+ T cells, CD20+ B cells and CD68+ macrophages. In this context, we analyzed the tissue with respect to the effective molecule MHC II,” Karin Klingel explains. She is the Academic Director at the University Hospital of Tübingen and the head of the cardiopathology and the infectious disease pathology department.

Crucial Progress in the Battle with Myocarditis

In doing so, the researchers found out that the amount of lymphocytes in children without myocarditis is smaller than that in adults without myocarditis. This is an important finding, according to the team led by Karin Klingel and Franziska Seidel. “We basically killed two birds with one stone here. On the one hand, our study has yielded significant evidence for an assessment and treatment of children and adolescents. On the other hand, this is in fact the first pediatric cohort for further research on myocarditis,” Franziska Seidel states, summarizing the findings. She is a study doctor at Deutsches Herzzentrum Berlin. In light of the disease, which is threatening for the young age group in particular, this is crucial progress regarding the improvement of the treatment and with respect to predicting the course of the disease.