To date, no transcatheter valve has been approved for placement in the pulmonary position in Japan. Consequently, percutaneous balloon dilatation may be advised for stenotic right ventricular outflow lesions; however, technical difficulties persist, particularly in adults. We describe the acute haemodynamic changes and outcome of balloon dilatation of right ventricular outflow obstruction using triple ultra-high pressure balloons. This is the first report of such a technical development, which seems to be safe and effective. A total of three adult patients, aged 25, 29, and 37 years, with severe conduit obstruction were referred for balloon dilatation. A triple ultra-high-pressure balloon technique was used in the three patients after unsuccessful double-balloon dilatation, or for highly calcified lesions, which were expected to require ultra-high pressure for effective relief. Following balloon dilatation, the pressure gradient decreased from 24, 30, 65 to 3, 25, 30 mmHg, respectively. There were no procedural complications except slightly increased pulmonary regurgitation. Balloon dilatation using a triple ultra-high pressure balloon technique can be a safe and effective palliative procedure for conduit obstruction in adult patients.

Accessory atrioventricular valvar tissue is uncommon and, on occasion, has been identified as a cause of ventricular outflow obstruction. Accessory tricuspid valvar tissue has been reported to cause subpulmonary obstruction but infrequently has accessory tissue arising from the mitral valve been associated with obstruction. This paper reports two cases of subvalvar obstruction; the first in association with a ventricular septal defect causing subaortic obstruction and the other in association with congenitally corrected transposition and a ventricular septal defect, causing subpulmonary obstruction.