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# Pulmonary right cusp

The right cusp is one of the three flaps of the pulmonary valve, the side facing the aorta; together they stop blood flowing back from the lungs.

Official name: Right semilunar leaflet of pulmonary valve

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## What it is

The right cusp of the pulmonary valve.

## What it does

One of the three cusps that seal the pulmonary valve.

## Key points

- Lies next to the aortic root; the pulmonary valve sits higher, more anterior and to the left of the aortic valve, at an angle to it
- Its commissure with the pulmonary left cusp faces the commissure between the [aortic right coronary cusp](https://durgical.com/en/anatomy/right-coronary-leaflet/) and [aortic left coronary cusp](https://durgical.com/en/anatomy/left-coronary-leaflet/)
- Pulmonary valve endocarditis is the rarest of the four valves

## Key facts

**Where**
Right (posterior) cusp of pulmonary valve, facing aortic root

**Attaches**
Crescent-shaped attachment to [pulmonary trunk](https://durgical.com/en/anatomy/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

**Behind**
Aortic root, near the aortic right and left coronary cusps

**In front**
[Pulmonary anterior cusp](https://durgical.com/en/anatomy/anterior-semilunar-leaflet-of-pulmonary-valve/), at the commissure

**Lateral**
[Pulmonary left cusp](https://durgical.com/en/anatomy/left-semilunar-leaflet-of-pulmonary-valve/), at the commissure facing the aortic root

**Below**
Outflow (infundibular) septum, separating the right ventricular outflow from the aortic root

## On imaging

Parasternal short- [axis](https://durgical.com/en/anatomy/axis/) echo and CT show it beside the aortic root; in transposition of the great arteries this side-by-side relation is lost and the vessels run parallel.

## 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

- Tetralogy of Fallot: the outflow septum is displaced forward, narrowing the infundibulum below this valve, which is often small and thick
- In pulmonary hypertension the cusps are usually normal; the loud P2 and regurgitation come from high pressure and a dilated trunk
- Typical valvar pulmonary stenosis has thin cusps fused at the commissures into a dome; balloon valvuloplasty, which tears the fused commissures, is the usual first treatment

## Development

It grows from half of a lateral outflow cushion; the other half of the same cushion becomes an aortic cusp, so the two valves are built side by side.

## 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.

## How is the pulmonary valve positioned relative to the aortic valve?

Higher, more anterior and to the left of the aortic valve, at an angle to it; the pulmonary right cusp lies next to the aortic root.

## Which of the four heart valves is least often affected by endocarditis?

The pulmonary valve.

## In tetralogy of Fallot, what narrows the outflow below the pulmonary valve?

The outflow septum is displaced forward, narrowing the infundibulum; the valve is often small and thick.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
valvula semilunaris dextra valvae trunci pulmonalis TA2 4010

**Official Spanish (DeCS)**
Valva semilunar derecha de la válvula pulmonar DeCS D011664

**English (TA2)**
Right semilunar leaflet of pulmonary valve

**Also called**
right adjacent leaflet of pulmonary valve · right semilunar cusp of pulmonary valve · velum semilunare dextrum

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.

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/right-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/right-semilunar-leaflet-of-pulmonary-valve/