Isolated myocarditis as a cause of sudden death in the first year of life

A series of three cases of isolated myocarditis, presenting as sudden death in infancy, occurred over a period of 3 months. This prompted a review of the autopsy records of the Children's Hospital of Winnipeg. Over a period of 40 years, 24 cases of isolated myocarditis were traced from 3196 autopsies. Most (21 of 24) cases of isolated myocarditis occurred in infants less than 12 months of age. In 16 of the infants there were either no antecedent clinical signs (sudden deaths), or a short clinical history of less than 24 h duration. Heart weights, however, were greater than the 99th percentile of published normals in three infants and above the 95th percentile in a further 16 infants. Areas of hypertrophied fibres were seen even in infants with a short history. These latter findings suggest that a latent phase of myocarditis may exist. The responsible pathogens were identified very rarely, due to a lack of suspicion of the existence of myocarditis, and it is suggested that samples of myocardium should be submitted for virologic examination in all cases of sudden death in the first year of life.