Pulmonary (pulmonic) stenosis
Pulmonary stenosis is virtually always a consequence of congenital heart disease. The stenosis can be fixed or dynamic, depending on the underlying etiology. Pulmonary stenosis can be valvular (i.e stenosis localized in the valve), subvalvular (stenosis proximal to the valve) or supravalvular (stenosis distal to the valve). Valvular pulmonic stenosis can be caused by dysplastic, bicuspid or unicuspid valves. Table 1 presents common causes of pulmonic stenosis.
Table 1. Causes of pulmonic stenosis.
|Tetralogy of Fallot|
|Transposition of the great arteries)|
|Dysplastic, bicuspid or unicuspid pulmonary valve|
|Noonan syndrome: 60% of all individuals with Noonan syndrome have pulmonic stenosis. The stenosis is subvalvular, causing a narrowing of the RVOT (right ventricular outflow tract).|
|Carcinoid heart disease: Carcinoid syndrome is a paraneoplastic syndrome that occurs due to carcinomas secreting kallikrein and serotonin. In the heart, this can lead to thickening of the pulmonary valve and, subsequently, narrowing of the valvular orifice. Carcinoid heart disease may also lead to endocardial fibrosis.|
|Rheumatic heart disease|
|Sinus of Valsalva aneurysm: The aneurysm may compress the pulmonary outflow.|
|Myxoma: Myxomas may compress the pulmonary outflow.|
|Aortic aneurysm: Aortic aneurysms may compresses the RVOT.|
Echocardiography in pulmonic stenosis
In the setting of pulmonary valve stenosis, the pressure in the right ventricle rises, which results in right ventricular hypertrophy. The valve is usually thickened and during systole leaflet doming appears. The proximal part of the pulmonary artery is frequently dilated.
The maximum and mean pressure gradient is calculated using continuous wave (CW) doppler placed along the pulmonary valve in the parasternal short-axis view (PSAX). The gradient is calculated using Bernoulli's simplified formula:
ΔP = 4v2
Pulmonary artery pressure (PA pressure)
The systolic pulmonary artery pressure (PA pressure, PASP) can be estimated by subtracting the pressure gradient across the valve (ΔP) from right intraventricular pressure. The systolic PA pressure is an indicator of cardiac hemodynamic status and may be estimated with echocardiography. The PASP is an independent predictor of survival and for elevated left ventricular filling pressures (Lam et al). PASP is elevated in pulmonary arterial hypertension (PAH).
The continuity equation can be used to calculate the valve area. The equation claims that the volume of blood flowing through the RVOT is equal to the volume flowing through the pulmonary artery.
SVRVOT = SVPA
SV = stroke volume.
The stroke volumes are calculated using cross-sectional area and VTI (Velocity Time Integral):
SVRVOT = areaRVOT × VTIRVOT
SVPA = areaPA × VTIPA
areaRVOT × VTIRVOT = SVPA = areaPA × VTIPA
The valve area (areaPA) is derived as follows:
areaPA = (areaRVOT × VTIRVOT) / VTIPA
Table 2. Grading of pulmonic stenosis.
|Grading of pulmonic stenosis||Maximum gradient||Maximum velocity|
|Small PS||<36 mmHg||<3 m/s|
|Moderate PS||36-64 mmHg||3-4 m/s|
|Pronounced PS||>64 mmHg||>4 m/s|
Table 3. Normal right heart hemodynamics
|RVSP/PASP Echo||< 36 mm Hg*|
|Mean PAP||8 – 20 mm Hg|
|PAEDP||4 – 12 mm Hg|
|RAP||0 – 5 mm Hg|
|PVR||< 2.0 – 3.0 WU|
*up to 40 mm Hg in older and obese patients.
Baumgartner et al: Echocardiographic assessment of valve stenosis: EAE/ASE Recommendations for Clinical Practice (2009. JASE).