Endocardial fibrosis in apparently normal infant hearts.

A classification of the histological appearance of the endocardium in infants, and observers' reproducibility tests have been carried out. In a retrospective survey of 262 overtly normal hearts, what is considered to be abnormal thickening of the endocardium was found in 3.4%, and probably significant thickening in 20%. The changes occurred in unexpected home deaths as well as in hospital deaths and the lesions may be a contributing factor in some cot deaths, but a prospective study is required to confirm this.