Extreme right ventricular hypoplasia after relief of severe pulmonary stenosis. Use of balloon catheter occlusion of atrial septal defect in assessing right ventricular function.

A patient is described in whom extreme right ventricular hypoplasia and right-to-left shunting through an atrial septal defect occurred after relief of severe pulmonary stenosis. The ability of the hypoplastic right ventricle to deal with an increased volume load was assessed at cardiac catheterisation by occluding the atrial septal defect with a balloon tipped catheter.