Pulmonary Stenosis
Anatomy
Pulmonary valve stenosis accounts for 8-10% of all congenital heart defects. The obstruction may be purely valvular, valvular with indundibular narrowing, or infundibular with a normal pulmonic valve. The stenosis may manifest as lesion projecting into the main pulmonary artery with fused valve leaflets. Less severe form occurs when only the edges of the cusps are fused leaving the symptoms to go unnoticed until later in life.
Pathophysiology
Obstructive lesions of the RV and pulmonary circulation do not provide RV with a decompensation route thus resulting in increased impedance and hypertrophy of the RV. The most severe form manifests shortly after birth with right ventricular pressure exceeding that of the left ventricle. Less sever form would gradually dilate the RV and result in cardiac failure later in life.
Stenosis is classified into mild, moderate, and severe on the basis of the pressure gradient across the pulmonary valve. A gradient of less than 25 mmHg is considered mild, 25-49 mmHg is considered moderate, and 50-79 mmHg is classified as severe, where >80 mmHg is critical.
Symptoms
Moderate pulmonary stenosis does not usually manifest for the first 2 to 3 years of life and later presents with fatigue and dyspnea. The severety of symptoms is directly related to the RV flow obstruction. In the presence of ASD, (i.e. right to left shunt) the cardiac output and pulmonary blood flow will be diminished resulting in cyanosis. Clinical features include a loud ejection murmur. In mild form of PS the EKG will be normal, and moderate PS will result in an abnormal EKG with dominant R waave and negative or upright T waves.
Surgical Intervention
Open valvotomy under direct vision through an incision in the PA and combined with an inflow occlusion provide excellent results. In a case of hypoxia (PaO2<30 mmHg)indicates a necessity of a systemic to pulmonary shunt. Intravenous prostaglandin in order to maintain ductal patency post-op may be required.
Older Children with isolated PS may benefit from balloon pulmonary vavulotomy performed off CPB via femoral venous catherer.
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