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Background
Pulmonary stenosis (PS) may be valvular, supravalvular or subvalvular. The most common form of PS is valvular which is congenital in origin and usually occurs as an isolated sporadic defect. Valvular PS, however, can occur in the setting of an autosomal dominant syndrome such as Williams, Noonan or Alagille Syndromes, as part of tetralogy of Fallot or following maternal infection with Rubella.
The pulmonary valve in valvular PS is typically thin and pliable and usually domes in systole due to varying degrees of fusion of the commissures. Less commonly, the pulmonary valve may be thickened and dysplastic and exhibit decreased mobility of its cusps without commissural fusion. As part of a tetralogy of Fallot repair or severe valvular PS, patients may have undergone a pulmonary valvotomy leaving them with severe free pulmonary regurgitation and the sequelae of right ventricular (RV) volume overload.
Supravalvular PS usually occurs with one of the aforementioned genetic syndromes or can be associated with tetralogy of Fallot or a ventricular septal defect (VSD). Branch pulmonary arteries may also be involved.
Subvalvular PS involves narrowing of the infundibulum and is typically seen with other cardiac defects such as tetralogy of Fallot or a VSD. Double-chambered right ventricle is considered to be another form of subvalvular PS.
The severity of PS or right ventricular outflow tract (RVOT) obstruction is graded by the peak gradient across the RVOT: trivial <25 mmHg, mild 25-49 mmHg, moderate 50-79 mmHg and severe >80 mmHg.
Symptoms rarely occur in the absence of severe PS. These symptoms include: exercise intolerance, fatigue, dyspnea, presyncope or syncope, symptoms of right-sided congestive heart failure, chest pain from RV ischemia or symptoms related to arrhythmias.
Trivial and mild valvular PS rarely progresses significantly. Symptomatic patients with severe (and sometimes moderate) PS will often require a percutaneous balloon (or surgical) valvotomy. Both supravalvular and subvalvular PS have been reported to progress and should be followed closely long-term as they may require an intervention should they become moderate-to-severe or the patient develops symptoms.
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