Response to experimental coarctation of the aorta and pulmonic stenosis in the fetal lamb.

The following conditions were surgically created in fetal lambs at the gestational ages of 80 to 90 days: (1) preductal coarctation, (2) postductal coarctation, (3) pulmonic stenosis, and (4) constriction of the ductus arteriosus. Studies performed at the time of delivery showed the following: Preductal coarctation and postductal coarctation often are associated with a dilated ductus arteriosus that remains patent. Pulmonic stenosis often results in prestenotic and poststenotic dilatation that may include the ductus arteriosus. The fetal ventricles become hypertrophied in response to the increased pressure work imposed by the distal stenoses.