Subpulmonic Membrane Associated with a Supracristal VSD: A Rare Cause of Right Ventricular Outflow Obstruction

Subpulmonary membrane: A rare cause of right ventricular outflow tract obstruction

Subpulmonary membrane is a rare cause of right ventricular outflow tract (RVOT) obstruction, and only a few case reports exist with or without associated ventricular septal defect. We report a series of three cases with subpulmonary membrane causing RVOT obstruction. Two of these have been operated (the first case operated after unsuccessful attempt at balloon dilatation), and the third case is on follow-up at present.

Rheology of right ventricular outflow tract obstruction: sub-pulmonary membrane developing months after primary intervention to treat pulmonary atresia with intact interventricular septum

Isolated sub-pulmonary membrane is a rare condition, the origin of which has been debatable. Transcatheter treatment of pulmonary valve atresia with intact interventricular septum by radiofrequency perforation and balloon dilatation to restore biventricular circulation is gaining more popularity, with improving results over time. We report in our experience of 79 cases in 10 years the development of a sub-pulmonary membrane in 4 cases: causing significant obstruction requiring surgical excision in one case that revealed a fibrous membrane on pathology; causing mild right ventricular outflow tract obstruction in another and not yet causing obstruction in 2. On cardiac MRI, the right ventricular outflow tract and the right ventricular outflow tract/pulmonary atresia angle showed no morphological abnormalities.

Successful balloon valvuloplasty of a subpulmonic membrane associated with cor triatriatum dexter: a case report

Background

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.

Case presentation

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).

Conclusions

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.

Discrete subpulmonic membrane in association with isolated severe pulmonary valvar stenosis

Background

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.

Case presentation

A 7 – year – old boy was referred to a tertiary care hospital with complaints of dyspnea on moderate exertion and palpitations of about 2 years duration. Physical examination revealed parasternal lift, systolic thrill and a 4/6 ejection systolic murmur, best heard over the left 2^nd intercostal space. His oxygen saturation was 88% on room air. Two-dimensional echocardiography showed a thickened pulmonary valve with fused leaflets that show severe systolic doming. There was a discrete subpulmonic membrane about 1.3 cm below the pulmonary valve annulus. Continuous wave Doppler interrogation showed peak systolic pressure gradient of 185 mmHg across the pulmonary valve. Balloon dilation of the pulmonary valve was performed and the pressure gradient came down to 50 mmHg. Follow-up transthoracic echocardiography showed residual pressure gradient of about 50 – 60 mmHg across the pulmonary valve. The residual pressure gradient appeared to be mainly subvalvar, as seen on the continuous wave Doppler tracing. The patient reported marked improvement in terms of exercise tolerance and subjective symptoms.

Conclusions

Association of subpulmonic membrane with severe pulmonary valvar stenosis, concordant ventriculoarterial connection and intact ventricular septum is rare. When it occurs, the result of percutaneous valve dilation may be suboptimal.