Subpulmonic membrane as a cause of right ventricular outflow tract obstruction in patients with concordant ventriculoarterial connection and intact ventricular septum is considered to be rare. Association with cor triatriatum dexter and success of subpulmonic balloon valvuloplasty have never been reported, at least to the best of our knowledge.
A 3-year-old Moroccan boy was referred to our tertiary care hospital with complaints of dyspnea on moderate exertion. A physical examination revealed parasternal lift, systolic thrill, and a 4/6 ejection systolic murmur, best heard over the left second intercostal space. His oxygen saturation was 99% on room air. Two-dimensional echocardiography showed a discrete circumferential membrane just below the pulmonic valve and a right atrial membrane. Continuous wave Doppler interrogation showed peak systolic pressure gradient of 85 mmHg across the subpulmonic membrane and no significant gradient across the right atrial membrane. Balloon dilation of the subpulmonic membrane was performed and the pressure gradient came down to 50 mmHg. During follow-up, he reported marked improvement in terms of exercise tolerance. Transthoracic echocardiography showed residual pressure gradient of approximately 40 mmHg across the membrane. Surgery resection of the two membranes was programmed, but he died after an extracardiac disease (appendicular peritonitis).
Subpulmonic membrane as an isolated cause of right ventricular outflow tract obstruction is rare. Its association with cor triatriatum dexter is even less common. The result of percutaneous balloon valvuloplasty of subpulmonic membrane is an interesting alternative while waiting for surgery. Surgery is currently the preferred modality of treatment with the resection of both right atrial and subpulmonic membranes.