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The birth prevalence of isolated pulmonary valvar stenosis is between 1/2,000-10,000 in Europe and, worldwide, accounts for between 5-8% of children born with a congenital heart defect (CHD).

Clinical presentation varies according to age. In neonates, critical pulmonary stenosis is diagnosed on signs of right heart failure associated with cyanosis due to supra-systemic pressures and right-to-left shunt through the oval foramen, with ductal dependency. In severe untreated forms, dyspnea or syncope on exercise can occur. However, most patients are asymptomatic and diagnosed on presentation of a heart murmur during infancy or childhood. Congenital pulmonary valvar stenosis is most often isolated, with usually thin leaflets, dome-shaped with a central narrow opening. In 6% of children it is associated with a genetic syndrome, with usually thick, dysplastic leaflets. The malformation can also be associated with several complex malformations such as double outlet right ventricle, transposition of the great arteries, and Ebstein anomaly of the tricuspid valve.

The etiology for isolated forms is unknown. Occasionally the malformation is associated with a genetic syndrome (typically the RASopathies) such as Noonan, LEOPARD or Costello syndromes, harboring mutations of gene PTPN11.

Echocardiography is the best diagnostic tool. It establishes the diagnosis, looks for other levels of right ventricular outflow tract obstruction, and usually provides sufficient information to plan the treatment. CT-scan or MRI can be useful to assess the anatomy of the subpulmonary infundibulum and pulmonary branches.

Differential diagnosis includes primary pulmonary causes of cyanosis in neonates, along with other cyanotic heart lesions, such as transposition of the great vessels and tetralogy of Fallot.

Diagnosis on prenatal ultrasound screening is possible but is only detected in approximately 40% of cases; the rate of detection could be improved by the use of color flow Doppler through the outflow tracts.

The risk of recurrence of isolated valvar pulmonary stenosis is low, ranging from 1.7 to 3.7%. Relative risk of recurrence of right ventricular outflow tract obstruction as a whole is high at 48.6%.

Percutaneous balloon valvuloplasty is the treatment of choice of isolated valvar pulmonary stenosis. When the valve is dysplastic with thickened leaflets, or when there is an associated subvalvar or supravalvar obstruction, surgical valvulotomy or valvulectomy is indicated.

The prognosis of mild forms of valvar pulmonary stenosis is good, with stability or even spontaneous decrease of the gradient with age. The prognosis after balloon valvuloplasty is usually excellent. In rare cases of residual or recurrent pulmonary stenosis, a second balloon valvuloplasty can be attempted with good success rates. If it fails, surgery is indicated. Severe pulmonary regurgitation at late follow-up is rare and may require pulmonary valvar replacement, percutaneous or surgical.