Myocarditis in infants and children: A review for the paediatrician.
Clinical myocarditis is uncommon in infants and children. The most common pathogen is Coxsackievirus B. The offending agent triggers an immune response, which results in myocardial edema with subsequent impairment of systolic and diastolic function. Newborns and infants are more severely affected because the immature myocardium has limited ways of adapting to an acute insult. Children typically present with sinus tachycardia and gallop on auscultation, cardiomegaly on chest x-ray and small voltages on electrocardiogram. The echocardiogram shows reduced ventricular function. Viral studies can isolate the pathogen. Myocardial biopsy is useful diagnostically, but carries a significant risk for the sick infant. The first line of treatment includes measures such as rest, oxygen and diuretics. Inotropic agents are useful in moderate to severe heart failure. The role of immunosuppressive therapy is not yet clearly established in the paediatric age group. Prognosis is guarded in newborns but more favourable in older children.
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Division of Pediatric Cardiology, Montreal Children's Hospital, McGill University, Montreal, Quebec.