Exercise-induced electrocardiographic changes in children with congenital aortic stenosis.

The relationship of exercise-induced electrocardiographic changes to severity of obstruction in congenital aortic stenosis was studied in 44 children. Twelve subjects, with ST segment depression of 1 mm or more lasting 0.08 seconds after the J Point, had left ventricular-aortic peak systolic pressure differences (gradients) ranging from 54 to 112 mm Hg. The remaining 32 children had less than 1 mm or no ST segment depression. Thirty-one of these had gradients ranging from 10 to 48 mm Hg and one had a gradient of 52 mm Hg. Vectorcardiograms, electrocardiograms, and chest roentgenograms were not useful in the identification of the severity of the lesion. The study suggests that children with severe gradients develop electrocardiographic ST segment changes with exercise, thereby helping to select those patients who should have catheterization studies to delineate the severity of the lesion. In those with a normal exercise test, cardiac catheterization may be safely delayed, but the exercise test should be repeated to identify those who develop progressive obstruction.