AbstractSix infants, four with transposition of the great arteries and one each with mitral atresia and tricuspid atresia, who did not improve following balloon atrial septostomy are presented. Each patient underwent transcatheter blade atrial septostomy with resultant improvement of interatrial mixing (immediate improvement in three transposition patients and delayed improvement in one) or interatrial obstruction (in the mitral and tricuspid atresia patients). It is suggested that blade atrial septostomy is a safe and effective technique for nonsurgical palliation of congenital heart defects to enlarge a restrictive interatrial communication, especially if balloon atrial septostomy has not been successful.