Membranous subvalvular pulmonary stenosis in complete transposition of the great arteries: usefulness of serial exercise testing.

A 22-year-old male who had Mustard repair for complete transposition presented with progressive exercise intolerance, documented by a gradual decrease in exercise capacity on cycle ergometer. Cardiac catheterization and angiography demonstrated subvalvular pulmonary stenosis. After surgical relief of the obstruction, exercise capacity returned to previous level.