[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Chest](https://durgical.com/en/anatomy/region/chest/) › Pulmonary left cusp [Cardiovascular system](https://durgical.com/en/anatomy/system/cardiovascular-system/) · [Chest](https://durgical.com/en/anatomy/region/chest/) # Pulmonary left cusp The left cusp is one of the three flaps of the pulmonary valve, facing the aortic root; it helps seal the valve after each heartbeat. Official name: Left semilunar leaflet of pulmonary valve [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=thorax&select=pulmonary_left_cusp&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The left cusp of the pulmonary valve. ## What it does One of the three cusps that seal the pulmonary valve. ## Key points - One of the two cusps facing the aortic root, with the pulmonary right cusp - The first septal branch of the [LAD (anterior descending artery)](https://durgical.com/en/anatomy/anterior-interventricular-artery/) runs just beneath the back of the pulmonary valve and is at risk when the valve is harvested (Ross procedure) - Pulmonary regurgitation in pulmonary hypertension (Graham Steell murmur): early diastolic, left upper sternal border, louder on inspiration ## Key facts **Where** Left (posterior) cusp of pulmonary valve **Attaches** Crescent-shaped attachment to pulmonary trunk root; nodule and lunules at free edge **Function** Closes in diastole, preventing backflow into [right ventricle](https://durgical.com/en/anatomy/right-ventricle/); valve heard best at left 2nd intercostal space ## Relations **In front** [Pulmonary anterior cusp](https://durgical.com/en/anatomy/anterior-semilunar-leaflet-of-pulmonary-valve/), at the commissure **Medial** [Pulmonary right cusp](https://durgical.com/en/anatomy/right-semilunar-leaflet-of-pulmonary-valve/), at the commissure facing the aortic root **Behind** [Left main coronary artery](https://durgical.com/en/anatomy/left-coronary-artery/) passing behind the [pulmonary trunk](https://durgical.com/en/anatomy/pulmonary-trunk/); the transverse pericardial sinus behind the root **Lateral** Tip of the left atrial appendage, curling up beside the pulmonary trunk ## On imaging Parasternal short- [axis](https://durgical.com/en/anatomy/axis/) echo at the base shows the pulmonary valve curving round the front of the aorta, with this cusp on the left; cardiac MRI and CT show the root and its relation to the coronary arteries. ## Common problems - Pulmonary stenosis, usually from birth; often treated with a balloon. - Leak after childhood repair of congenital heart disease. ## How it is diagnosed Echocardiogram; cardiac MRI. ## Treatment - Balloon valvuloplasty or valve replacement (surgical or by catheter). ## Clinical notes - In the Ross procedure, dissection near the back of the pulmonary root risks the first septal perforator and the left main coronary artery - After tetralogy of Fallot repair with a patch across the annulus, free pulmonary regurgitation slowly dilates the right ventricle; valve replacement may be needed later - Before a transcatheter pulmonary valve is implanted, a balloon is inflated in the outflow tract while coronary angiography checks that the left coronary artery behind the root is not squeezed ## Development Like the right cusp, it forms from half of a lateral outflow cushion split by the spiral outflow septum; misalignment of that septum underlies tetralogy of Fallot and related outflow defects. ## Related conditions - [Pulmonary valve stenosis](https://durgical.com/en/conditions/pulmonary-valve-stenosis/) ## Test yourself Think of the answer, then tap the question to see it. ## What is the Graham Steell murmur? Pulmonary regurgitation in pulmonary hypertension: an early diastolic murmur at the left upper sternal border, louder on inspiration. ## Which arteries are at risk when the pulmonary valve is harvested in the Ross procedure? The first septal branch of the LAD, just beneath the back of the valve, and the left main coronary artery behind the pulmonary trunk. ## What happens after tetralogy of Fallot repair with a patch across the pulmonary annulus? Free pulmonary regurgitation slowly dilates the right ventricle, and valve replacement may be needed later. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/left-semilunar-leaflet-of-pulmonary-valve/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** valvula semilunaris sinistra valvae trunci pulmonalis TA2 4011 **Official Spanish (DeCS)** Valva semilunar izquierda de la válvula pulmonar DeCS D011664 **English (TA2)** Left semilunar leaflet of pulmonary valve **Also called** left adjacent leaflet of pulmonary valve · left semilunar cusp of pulmonary valve · velum semilunare dorsale Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=12101); [Anatomy, Thorax, Heart Pulmonic Valve](https://www.ncbi.nlm.nih.gov/books/NBK547706/); Anatomy of the Human Body (20th ed.): Development of the Vascular System (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain. ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/left-semilunar-leaflet-of-pulmonary-valve/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/left-semilunar-leaflet-of-pulmonary-valve/