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# Valve rings (fibrous skeleton)

The valve rings form the heart's fibrous skeleton; they hold the valves in shape and insulate the atria from the ventricles electrically.

Official name: Fibrous rings of the heart valves

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## What it is

Tough rings of fibrous tissue at the base of the valves, joined into the heart's 'skeleton'.

## What it does

Hold the valves' shape and electrically insulate the atria from the ventricles, so the signal can only cross at the AV node.

## Key points

- The right fibrous trigone and the membranous septum together form the central fibrous body, the strongest part of the cardiac skeleton
- The mitral annulus is saddle-shaped, not flat; repair rings restore its size and shape
- Accessory pathways that cross the annuli outside the AV node cause pre-excitation (Wolff–Parkinson–White) and are ablated at the annulus
- The aortic and pulmonary cusps hinge on a crown-shaped line, not a flat ring; the aortic annulus measured on CT before transcatheter implantation is a virtual ring through the lowest cusp hinges

## Key facts

**Where**
Fibrous skeleton between atria and ventricles: mitral, tricuspid, aortic and pulmonary rings; right and left fibrous trigones

**Attaches**
Valve leaflets and cusps; atrial and ventricular myocardium

**Function**
Supports valve shape; electrically insulates atria from ventricles (AV bundle pierces right fibrous trigone)

## Relations

**In front**
Pulmonary ring, the highest and most anterior, joined to the aortic ring by the conus ligament

**Behind**
[Coronary sinus](https://durgical.com/en/anatomy/coronary-sinus/) along the mitral ring, [Circumflex artery](https://durgical.com/en/anatomy/circumflex-artery-of-heart/) in the left atrioventricular groove and [right coronary artery](https://durgical.com/en/anatomy/right-coronary-artery/) around the tricuspid ring

**Below**
Ventricular muscle below and atrial muscle above; only the [bundle of His](https://durgical.com/en/anatomy/atrioventricular-bundle/) crosses between them

## How to find it

On the [chest](https://durgical.com/en/anatomy/region/chest/) wall the rings lie on an oblique line behind the [sternum](https://durgical.com/en/anatomy/sternum/): pulmonary highest, at the left 3rd sternocostal joint; aortic a little lower and medial; mitral behind the left half of the sternum at the 4th cartilage; tricuspid lowest, behind the sternum at the 4th space. Murmurs are heard downstream, at the auscultation areas.

## On imaging

Echo measures annular diameters (tricuspid annular dilation guides repair) and TAPSE, the systolic movement of the lateral tricuspid annulus toward the apex, a measure of right ventricular function. CT measures the aortic annulus before transcatheter valves.

## Common problems

- The mitral and tricuspid rings stretch when the heart enlarges, making the valves leak.

## Treatment

- An annuloplasty ring sewn into the annulus is part of most valve repairs; TAVR valves are sized to the aortic annulus.

## Clinical notes

- Mitral annular calcification, common in older people, can extend into the conduction system and complicates valve surgery
- Annuloplasty stitches near the trigones, the coronary sinus and the circumflex artery risk the conduction system and the coronary circulation
- Endocarditis abscess spreads through the fibrous skeleton toward the central fibrous body and can cause AV block

## Development

Fibrous tissue from the atrioventricular groove and the cushions grows in and cuts the early muscle continuity between atria and ventricles; a strand of muscle left across it becomes an accessory pathway.

## Related conditions

- [Infective endocarditis](https://durgical.com/en/conditions/infective-endocarditis/)
- [Mitral regurgitation](https://durgical.com/en/conditions/mitral-regurgitation/)
- [Aortic regurgitation](https://durgical.com/en/conditions/aortic-regurgitation/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which structures form the central fibrous body of the heart?

The right fibrous trigone and the membranous septum; it is the strongest part of the cardiac skeleton.

## What is the electrical role of the fibrous skeleton, and what normally crosses it?

It insulates the atria from the ventricles; only the bundle of His crosses, piercing the right fibrous trigone.

## What causes Wolff–Parkinson–White pre-excitation, and where is it ablated?

An accessory pathway crossing the valve annuli outside the AV node; it is ablated at the annulus.

## What shape is the mitral annulus, and what do repair rings restore?

Saddle-shaped, not flat; annuloplasty rings restore its size and shape.

## What does TAPSE measure?

The systolic movement of the lateral tricuspid annulus toward the apex, a measure of right ventricular function.

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

## Its names

**Official Spanish (DeCS)**
Anillos fibrosos del corazón

**English (TA2)**
Fibrous rings of the heart valves

Sources: [Anatomy, Thorax, Heart](https://www.ncbi.nlm.nih.gov/books/NBK470256/); Anatomy of the Human Body (20th ed.): Surface Markings of the Thorax (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain; Tratado de anatomía humana (9.ª ed.), tomo II, Libro IV Angiología, sección 1, capítulo 1: Corazón, artículos I–VI.

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Representative model, for educational purposes only.

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