Diagnostic and Therapeutic Options in Myocarditis and Inflammatory Cardiomyopathy.

Myocarditis and inflammatory cardiomyopathy are inflammatory diseases of the heart muscle that can have both infectious and non-infectious causes. They can be caused by an unresolved viral infection or other infection, or they can be autoimmune, toxic, or allergic in nature. The specific identification of the pathogen and/or confirmation of inflammation can only be achieved through direct tissue analysis using endomyocardial biopsy (EMB), as neither detection of the virus nor assessment of the quality and intensity of the inflammation is possible using non-invasive methods. Accordingly, the removal and analysis of an EMB is considered the diagnostic gold standard in international guidelines and statements. The sudden onset of atypical angina pectoris and initially exertion-dependent dyspnea, as well as arrhythmias, pericardial effusion, and progressive symptoms of heart failure, indicate an acute inflammatory process of the myocardium. In addition, nonspecific symptoms such as fatigue and reduced physical performance may also occur. Diagnostic evaluation includes an electrocardiogram (ECG), cardiac imaging, and laboratory tests. The analysis of the EMB is crucial for a definitive diagnosis and thus for the initiation of an etiology-based, specific and personalized therapy. This includes histological and immunohistochemical inflammation diagnostics as well as molecular virological diagnostics. These enable both the detection of viruses and the assessment of transcriptional virus activity. New analyses using metagenomic next generation sequencing (NGS) techniques provide insights of enormous diagnostic and therapeutic relevance. This applies both to the spectrum of detectable pathogens and to the possibility of confirming transcriptional viral activity. In addition, gene expression profiling enables the differentiation of specific forms of myocardial inflammation (e.g., giant cell myocarditis, cardiac sarcoidosis, and eosinophilic myocarditis) and reduces the influence of "sampling errors" in focal inflammatory processes. The treatment of heart failure or ventricular arrhythmias is always symptomatic according to general evidence-based guidelines. In severe cases, mechanical circulatory support or even a heart transplant may be necessary. Patients with histologically confirmed myocardial inflammation or intramyocardial viral infection can be offered specific, causal, and personalized therapy. These patients can be successfully treated with immunosuppressive or antiviral therapy, which significantly improves the prognosis of the disease.