Abstract
Controlled observations of the effect of a standard exercise test on blood pressure were made in 26 cases of uncomplicated patent ductus arteriosus before and after surgical ligation. In this investigation the exercise test offered little information of value in diagnosis. Following the ligation there was a transitory fall in diastolic blood pressure after exercise in half the cases. This finding contrasted with the effect of exercise in the control group in which the diastolic pressure was elevated or remained unchanged in 90%. A sharp fall in diastolic blood pressure after exercise is no criterion that the ductus has recanalized.