Biventricular hypoplasia with myocardial fiber hypertrophy and disarray.

An 8-year-old girl with a long history of cardiac disease had restrictive filling of both ventricles, severe atrioventricular valve regurgitation, and extreme dilation of both atria. At necropsy the inflow areas of both ventricles were small, and part of the left ventricle lacked compact myocardium. Histology revealed myofiber hypertrophy and focal dysplasia (disarray) in both ventricles. The findings suggest an abnormality of cardiac development that occurred before gestation week 5.