Pulmonary Valvular Stenosis

Severity

• Mild: Peak gradient <36 mm Hg 

• Moderate: Between 36 and 64 mm Hg 

• Severe stenosis: >64 mm Hg

• Critical stenosis: Inadequate anterograde flow through RVOT. Prostaglandin-E1 dependent for pulmonary blood flow. 

• The end-spectrum of pulmonary stenosis is pulmonary atresia (complete obstruction). 

• Reference: https://www.ncbi.nlm.nih.gov/books/NBK560750/ and https://pmc.ncbi.nlm.nih.gov/articles/PMC10320808/ 

Hemodynamics in Critical Pulmonary Stenosis with a large VSD and a large PDA or Aortic Atresia with a large PDA

Pulmonary atresia with a VSD and a PDA:

• Qp/Qs Example Calculation: 

  • Aortic saturation is 85%, Pulmonary Artery saturation is the same because fed by the left to right PDA (85%)

  • Assuming a normal systemic A-V difference (oxygen consumption in the systemic compartment) of 30%, then vena cava saturations will be approximately 55% (85-30). 

  • Pulmonary vein saturation is 100% if no V/Q mismatch 

  • Then Qp/Qs = (Aortic Sat - Mixed Venous Sat) / (Pulm Vein Sat - Pulmonary Artery Sat) = (85-55)/(100-85) = 30/15 = 2/1. 

  • Clinical Paradox: Patients can be cyanotic (blue) yet present with symptoms of hyper-flow (e.g., dyspnea) due to elevated pulmonary blood flow by the PDA and high filling pressures. This emphasizes that cyanosis does not directly correlate with low pulmonary blood flow in all congenital heart diseases. ◦

  • Morphological Consequences: High pulmonary flow can lead to dilated left atrium and left ventricle. The management of oxygen administration in these children is complex since it can further vasodilate the pulmonary vascualture, and requires careful consideration once the diagnosis is established

Pulmonary Atresia with VSD (PA-VSD)

Pulmonary Atresia with VSD (PA-VSD) is the extreme of pulmonary stenosis. In the French world, they call it "APSO" (atrésie pulmonaire à septum ouvert) or Pulmonary Atresia with Open Septum. Some may also classify this entity as "extreme Tetralogy of Fallot" or Tetralogy of Fallot with Pulmonary Atresia. Indeed, this entity is genetically and embryologically related to Tetralogy of Fallot (often called "Tetralogy of Fallot with pulmonary atresia" by Anglo-Saxons). In fetal life, similar to Tetralogy of Fallot, the intrinsic properties of the ventricles (diastolic filling, systolic contractility) remain unchanged if the interventricular communication is non-restrictive. Both ventricles face the same afterload and are preloaded identically. In PA-VSD, since the pulmonary artery is atretic, all blood must traverse the ascending aorta. Foetal perfusion remains normal, and there is no coarctation because there is enough flow going through the LVOT, Ascending Aorta, Cerebral/Coronary vessels, and eventually to the descending arch via the isthmus. The key change is in the ductus arteriosus: it becomes the primary pathway for perfusing the pulmonary arteries, carrying blood retrograde from the aorta to the pulmonary branches. This altered flow and direction changes the morphology of the ductus arteriosus. Instead of forming a typical second arch, it often arises from the concavity of the aortic arch and takes a complex, tortuous, or looped shape, demonstrating that blood flow not only determines diameter but also models the vessel's form. This morphological alteration has critical clinical implications: stenting such a ductus arteriosus becomes significantly more challenging, often requiring alternative approaches (e.g., carotid or innominate artery access) rather than the standard femoral approach.

Echocardiography indicating pulmonary valvular stenosis

Measurement of the left to right PDA. The CW-doppler indicates that the profile is left to right and with a peak gradient in systole of 30 mmHg. Knowing that the systolic blood pressure of the newborn was 60 mmHg, one can assume that the systolic pulmonary arterial pressure is about 30 mmHg. The gradient through the valve was 90 mmHg, indicated that the RV peak systolic pressure was around 120 mmHg. The RV is suprasystemic. 

The CW-Doppler indicates a gradient through the valve of 82-92 mmHg. This indicates a significant obstruction. 

Visualization of the valve in 2D still frame, with measurements below of the opening (orifice). The measurement is often difficult to make in newborns due to non-homogeneous opening of the valve. The orifice is not circular but irregular in shape. 

Balloon dilatation of the pulmonary valves by catheterism

Presentation by Dr Shiran Moore and Mrs Laila Wazneh on pulmonary valvular stenosis