Myocarditis in Childhood: An Update on Etiology, Diagnosis and Management

Myocarditis is the term used to describe acute or chronic inflammation of the myocardium. For two decades, there has been increasing confrontations concerning the diagnosis, management and clinical outcome of the myocarditis. The cause of myocarditis frequently remains unknown. However, infections, systemic diseases, toxins and drugs have been reported being associated with inflammation of the myocardium (Kearney et al., 2001 & Mahrholdt H et al, 2006). The majority of cases are supposed to be due to infectious agents and it was recognized that any infectious agents could initiate myocarditis (Brodison & Swann, 2001). In North America and Europe, viral infection is the most common causes of myocarditis (Magnani & Dec, 2006). The true overall incidence of myocarditis remain obscure due to inconsistency of its definition and clinical manifestation in the paediatric population. Post-mortem study from Sweden reported incidence of myocarditis to be 1.06 % in 12.747 consecutive autopsies (Gravanis & Sternby, 1991). Since the clinical presentation of myocarditis is so variable, high index of suspicion is essential. Patients are asymptomatic and diagnosis is incidental in the majority of cases. The spectrum of disease ranges from nonspecific findings (chest pain, fever, myalgia, atrial or ventricular tachycardia) to acute heart failure and sudden death. Myocarditis as a cause of sudden death has been reported in up to 12% of young adults (Doolan et al., 2004). However, population based study from Finland (Kyto et al, 2007) documented that the incidence of fatal myocarditis (1.59 per 100000) was highest in infants under one year of age and incidence was lowest in young adults (5-24 years, 0.12-0.17/100000). Recently, Weber et al have also suggested that myocarditis is an infrequent, corresponding to approximately 2% of paediatric deaths (Weber et al., 2008). Previous researches (Felker et al, 1999 & Lipshultz et al, 2003) strongly suggested that acute myocarditis may proceed to dilated cardiomyopathy. Diagnostic evaluation of a series of 1.278 patients (mean age: 50 years, range 15-87 years) with cardiomyopathy revealed that 9.8% of cases was diagnosed with myocarditis (Felker et al, 1999). In a paediatric study assessing the incidence of cardiomyopathy, viral myocarditis was found to be responsible for 27% of cases with dilated cardiomyopathy (Lipshultz et al, 2003). Moreover, in a prospective cohort study (Towbin et al, 2006), it has been shown that most common known cause of dilated cardiomyopathy is myocarditis (46%). Several mechanisms were postulated for progression of myocarditis to dilated cardiomyopathy, including direct viral injury,