Válvula Semilunar Pulmonar: Anatomia, Função e Papel Circulatório

The pulmonary valve (semilunar) regulates flow from right ventricle to pulmonary artery.

Anatomy

• Three semilunar cusps (anterior, left, right) — fibrous tissue covered by endothelium.
• No chordae tendineae or papillary muscles (unlike AV valves).
• Located at pulmonary trunk origin; sinuses of Valsalva give rise to coronary arteries (rarely).

Function

• Systole: RV pressure > PA pressure → cusps open → ejection.
• Diastole: PA pressure > RV pressure → cusps close (P₂ component of S₂) → prevents backflow.

Clinical Correlates

• Pulmonary stenosis: Narrowed orifice → RV hypertrophy, systolic ejection murmur.
• Pulmonary regurgitation: Incomplete closure → diastolic decrescendo murmur (Graham Steell if PAH).
• Tetralogy of Fallot: Pulmonary stenosis + VSD + overriding aorta + RVH.
• Congenital absence: Rare; severe PAH.

Assessment

Echo: peak velocity, gradient, regurgitant jet. MRI: flow quantification. Cath: direct pressures.

Essential for low-pressure pulmonary circulation efficiency.