Overview

Number of cusps3 (anterior, right, left)

Auscultation area2nd left intercostal space, parasternal

Each semilunar cusp is a pocket-like fold of endocardium with a fibrous core. It has a thickened nodule at the centre of its free edge and thin crescent-shaped lunules on either side. When the valve closes, the lunules press together and the nodules meet in the middle to seal it. Behind each cusp the wall of the pulmonary trunk bulges slightly to form a pulmonary sinus. Unlike the aortic sinuses, these give rise to no arteries.

The pulmonary valve is the most anterior and superior of the four valves. It lies behind the medial end of the left 3rd costal cartilage, in front of and to the left of the aortic valve.

It closes at the end of right ventricular ejection, producing the P2 component of the second heart sound. During inspiration more blood returns to the right heart, right ventricular ejection lasts longer and P2 is delayed. This is physiological splitting of the second heart sound.

Location: At the top of the conus arteriosus, behind the left 3rd sternocostal junction. It is best heard in the 2nd left intercostal space beside the sternum.

Parts & subdivisions

Anterior, right and left semilunar cusps
Each has a central nodule and two lunules.
Pulmonary sinuses
Bulges of the trunk wall behind each cusp.

Function

Allows the right ventricle to eject into the pulmonary trunk.
Prevents blood flowing back into the right ventricle during diastole.

Clinical significance

Pulmonary stenosis

Pulmonary stenosis is usually congenital. It can occur alone, with Noonan syndrome or as part of tetralogy of Fallot. It produces an ejection systolic murmur at the upper left sternal edge, often with an ejection click, wide splitting of S2 and right ventricular hypertrophy. It is usually treated by balloon valvuloplasty.

Pulmonary regurgitation

Pulmonary regurgitation occurs in pulmonary hypertension, where it produces a high-pitched early diastolic murmur (Graham Steell murmur). It is also common after repair of tetralogy of Fallot, and long-standing regurgitation dilates the right ventricle.

Ross procedure

In the Ross procedure, the patient's own pulmonary valve is moved into the aortic position (an autograft). The pulmonary valve is then replaced with a donor valve (homograft).

Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.