Introduction:
Viral infections are considered the most frequent cause of myocarditis and dilated cardiomyopathy (DCM).

Material and methods:
We investigated the changes in viral presence and the impact of viral genome persistence in the myocardium on echocardiographic parameters, functional status and some laboratory parameters in a 6-month follow-up. Fifty-four patients with recent onset DCM, left ventricular ejection fraction < 40% and biopsy-proven myocarditis (> 14 mononuclear leukocytes/mm2 and/or > 7 T-lymphocytes/mm2) were enrolled. Polymerase chain reaction (PCR) was performed to detect pathogens in the myocardium. Patients were divided according to the administered therapy: standard heart failure medication (46 patients) and immunosuppressive therapy (8 patients).

Results:
In the standard heart failure medication group viral clearance was observed in 13 patients and viral persistence in 24 patients in the follow-up period. Comparing both groups, there was no statistically significant difference – LVEF improvement of 12.0 ±11.4% vs. 18.3 ±12.6%, decrease in NYHA class of 0.7 ±0.7 vs. 1.0 ±0.7, decline in NT-proBNP of 1335 ±1933 ng/l vs. 1942 ±3242 ng/l and decrease in infiltrating leukocytes of 11.1 ±15.8 vs. 6.7 ±23.0 cells/mm2 and T-lymphocytes of 5.8 ±15.1 vs. 1.8 ±10.9 cells/mm2 (all p = NS). A decrease in PCR positive patients from 37 to 29 was observed. The number of PVB19 positive PCR findings decreased from 5 to 4 in patients with immunosuppressive therapy.

Conclusions:
A decrease in the number of positive PCR findings in control endomyocardial biopsy was observed. Viral genome persistence was not associated with worse outcome in short-term follow-up.