2 The procedure
2.1.1 The right ventricular outflow tract includes the pulmonary valve and the tissue above and below it. Narrowing (stenosis) of this region may involve the area below the valve (subvalvar), the valve itself (valvar), or the area above the valve (supravalvar). Balloon dilatation of valvar right ventricular outflow tract narrowing (pulmonary valve stenosis) is covered in separate guidance.
2.1.2 Congenital subvalvar and supravalvar right ventricular outflow tract stenosis usually occurs with other cardiac defects, such as ventricular septal defect or tetralogy of Fallot. Postoperative right ventricular outflow tract obstruction may occur after surgery to create a conduit between the right ventricle and pulmonary artery in children with congenital anomalies. Narrowing may also occur beyond the right ventricular outflow tract, in one of the pulmonary arteries, or in their branches.
2.1.3 Standard treatment of non-valvar right ventricular outflow tract or pulmonary artery obstruction involves open chest surgery.
2.2.1 Balloon dilatation is a minimally invasive procedure that involves inserting a catheter into a large blood vessel, usually in the groin, and passing it up to the area of narrowing under radiological guidance. A balloon is then inflated within the narrowing to dilate the obstruction. Stenting involves the insertion of a small tube into the narrow region following balloon dilatation, to maintain patency.
2.3.1 No comparative studies were identified. Reports of technical success rates (defined as > 50% increase in pre-dilatation diameter, > 50% decrease in pressure gradient or > 20% decrease in right ventricular to aortic peak pressure ratio) were 97% (77/79) for stent insertion and 60% (97/162) for balloon dilatation in one study, and 53% (39/74) for balloon dilatation in another study. For more details, refer to the Sources of evidence section.
2.3.2 The Specialist Advisors had no concerns regarding the efficacy of this procedure.
2.4.1 One of the studies reported a 3% (5/162) complication rate for patients undergoing balloon dilatation. This included one femoral vein thrombosis, three pulmonary artery major dissections, and one transient pulmonary oedema. One study of stent implantation reported a complication rate of 1% (1/79 – a pleural perforation with haemopericardium). For more details, refer to the Sources of evidence section.
2.4.2 The Specialist Advisors listed potential complications as arrhythmia, haemorrhage, stent migration, embolisation, balloon rupture, blood vessel damage and tricuspid valve damage.