Myocarditis in children and detection of viruses in myocardial tissue: Implications for immunosuppressive therapy

Background There is scarce information on the potential benefits of immunosuppression in children with myocarditis and viral genomes in myocardium. We investigated the occurrence of myocarditis in children with a preliminary diagnosis of dilated cardiomyopathy, the frequency of cardiotropic viruses in the myocardium, and the response to immunosuppression. Methods Thirty patients (nine months to 12years) with left ventricular ejection fraction of 22.8±4.1% were subjected to right cardiac catheterization and endomyocardial biopsy. Specimens were analyzed for the presence of inflammatory elements (Dallas criteria) and viral genome (polymerase chain reaction). Patients with active myocarditis received immunosuppressants (azatioprine and prednisone) and were re-catheterized nine months later. A historical control group of nine patients with myocarditis who did not receive immunosuppressants was included. Results Active myocarditis was diagnosed in ten patients (five with viral genomes detected). Immunosuppression resulted in a significant increase in left ventricular ejection fraction from 25.2±2.8% to 45.7±8.6% (versus 20.0±4.0% to 22.0±9.0% in historical controls, p<0.01) and cardiac index from 3.28±0.51L/min/m2 to 4.40±0.49L/min/m2 (versus 3.50±0.40L/min/m2 to 3.70±0.50L/min/m2 in controls, p<0.01), regardless of the presence of viral genomes (p=0.98 and p=0.22, respectively for the two variables). No relevant clinical events were observed. Non-inflammatory cardiomyopathy was diagnosed in 20 patients (seven with viral genomes). While on conventional therapy, there were four deaths and three assignments to transplantation, and no improvement of left ventricular ejection fraction in the remaining ones (22.5±3.6% to 27.5±10.6%). Conclusion Children with chronic myocarditis seem to benefit from immunosuppressive therapy, regardless of the presence of viral genome in the myocardium.