congenital pulmonary stenosis

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Congenital pulmonary stenosis (CPS) refers to congenital narrowing of the right ventricular outflow tract, pulmonary valve, or pulmonary artery.

See pulmonary valve stenosis for a general discussion about this valvulopathy.

Epidemiology

The estimated incidence is 1 in 2000 births.

Pathology

Can be morphologically categorized depending on the relationship to the pulmonary valve :

supra valvular: distal to the valve: commonest ~60%
valvular
subvalvular: infundibular

Sub-classification

Supravalvular stenoses have been traditionally classified into four types.

Associations

Generally, occurs as an isolated feature and associations are rare . They include:

Radiographic features

Plain radiograph

Findings on chest radiographs are not specific. Can have a normal heart size or may show evidence of right ventricular hypertrophy. May also show evidence of a dilated pulmonary trunk or a main pulmonary artery. Pulmonary vascularity is often normal in mild cases. In some cases of pulmonary valvular stenosis, the flow of blood through the stenotic valve preferentially enters the left pulmonary artery which may result in an enlarged left pulmonary artery and slightly increased left lung vascularity, known as Chen sign.

Echocardiography

Right ventricular dysfunction and right atrial enlargement may occur due to the chronic pressure overload on the right-sided circulation. Specific features depend on the etiology, which affects the level at which the obstruction to right ventricular outflow occurs:

valvular pulmonic stenosis
- most common cause level of obstruction
- thickened and/or structurally abnormal valve leaflets
- leaflets often demonstrate systolic doming
subvalvular pulmonic stenosis
- double-chambered right ventricle (DCRV)
  - right ventricle functional subdivision into a chamber upstream to and downstream of the stenosis
  - best demonstrated in modified apical five-chamber or parasternal short-axis view
  - color flow Doppler shows aliased flow within the RV
  - fibromuscular band extending from the interventricular septum to the RV free wall
  - associated commonly with a VSD (especially membranous)
- infundibular pulmonic stenosis
  - protrusion of the infundibular septum into the right ventricular outflow tract
  - often associated with high amplitude "fluttering" of the pulmonary valve leaflets
supravalvular pulmonic stenosis
- parasternal short axis at the level of the aortic valve with a clockwise tilt should be utilized to visualize the main PA
- luminal narrowing and/or intraluminal echogenic membrane above the pulmonary valvular annulus

CT/CTA

Direct visualization of stenotic segment +/- post stenotic dilatation of distal arterial segments.

MRI/MRA

Direct visualization of stenotic segment +/- associated features. Velocity encoded phase contrast (VEC) cine sequences can assist assessing the severity of the stenosis by allowing measurement of blood flow velocities and volumes .