16 Pulmonary Valvar Stenosis
With Christian J. Kellenberger
Definition and Classification
- Pulmonary valvar stenosis occurs with a reduced orifice of the pulmonary valve due to fusion of the thickened valve leaflets. The valve can also be bicuspid and have a hypoplastic annulus. Stenosis of the dysplastic valve is typically seen in Noonan syndrome.
- Isolated or associated with subvalvar, supravalvar, or peripheral branch pulmonary artery stenosis
- Critical pulmonary stenosis refers to obstruction resulting in suprasystemic right ventricular systolic pressures, tricuspid regurgitation, and a right-to-left shunt across the atrial septum, and often pulmonary circulation is dependent on the flow through the ductus arteriosus.
Pathophysiology
- Increased impedance to right ventricular outflow requires increased right ventricular pressure to maintain pulmonary circulation.
- Increasing pressure results in concentric hypertrophy of the right ventricle and loss of compliance with impaired diastolic filling.
- Systolic pressure in the right ventricle and degree of hypertrophy are proportional to the degree of obstruction in the absence of heart failure.
- Severity of the lesion is generally classified according to the right ventricular systolic pressure.
- Less severe obstruction is well tolerated with gradual hypertrophy and dilatation of the right ventricle and preserved right ventricular function.
- More severe obstruction leads to suprasystemic right ventricular pressures, moderate dilatation of the right ventricle, and right heart failure.
- Right atrium may also become hypertrophied and dilated with tricuspid valve regurgitation.
- Increasing right atrial pressures leads to right-to-left shunting at atrial level if foramen ovale is patent or an atrial defect is present.
Clinical Manifestations