Viral myocarditis is an inflammatory disease of the heart which can result in cardiac failure, chronic cardiomyopathy and death. It is a three-phase process, consisting of an acute phase, sub-acute phase and a resolution/chronic phase. In our current study we prospectively investigated cardiac and inflammatory associated miRNAs levels in eight pediatric patients within the clinical course of VM. Samples were obtained within the three stages of the disease. Plasma levels of cardiac associated miR-208a, -208b, -499 and inflammatory associated miR-21, -146a, -146b, -155 were subsequently assessed using real-time polymerase chain reaction. The level of cardiac associated miR-208a was significantly elevated during the acute phase in comparison to the subacute and the resolution/chronic phases (3.8-fold, p < 0.02 and 3.1-fold, p < 0.02, respectively). The level of inflammatory associated miR-21 was significantly elevated during the acute phase in comparison to the resolution/chronic phase (2.0-fold, p<0.02). Moreover, cardiac associated miR-208b levels during the subacute phase correlated with systolic left ventricular function recovery during the chronic/resolution phase (ρ = -0.847, P = 0.016). In conclusion, cardiac damage significantly alters the expression of miR-208a and miR-21 during the pathological progression of myocarditis and miR-208b levels displays prognostic significance for left ventricular functional recovery.
