The mitral valve is one of the four main valves of the heart, located between the left atrium and left ventricle. Mitral regurgitation occurs when the mitral valve does not close properly and allows blood to flow backward from the left ventricle into the left atrium. Mitral valve annuloplasty rings are medical devices that are used to repair the mitral valve and treat mitral regurgitation. These rings are placed around the base or annulus of the mitral valve to reshape and stabilize the valve opening. This helps the leaflets come together properly during ventricular contraction to prevent backflow of blood.
Types Of Mitral Valve Annuloplasty Rings
There are several types of annuloplasty rings available based on their material and design:
Rigid Rings: Made of non-flexible materials like metal alloys or rigid polymers. They maintain a fixed size and shape after implantation to repair the mitral valve annulus. Commonly used rigid ring materials include titanium and pyrolytic carbon.
Semi-Rigid Rings: Composed of relatively stiff but flexible materials that allow for some deformation. They provide stability while also accommodating certain changes in annular size and shape during the cardiac cycle. Examples are Physio rings made of polyester.
Flexible Rings: Manufactured from highly flexible and compliant materials like Gore-Tex that reshape and remodel according to dynamic changes in the annulus. Flexible rings like Cosgrove-Edwards ring allow dynamic annular mobility.
Adjustable Rings: Allow surgeons to adjust and resize the ring after implantation for a customized fit using sizing devices. Examples are Medtronic Myxo ETlogix and Edwards MC3 rings.
Saddle-Shaped Rings: Have a curved saddle design that matches the physiological saddle shape of the mitral annulus for a congruent repair. Examples are Edwards physiological annuloplasty rings.
Mechanism Of Action Of Mitral Valve Annuloplasty Rings
Annuloplasty rings work by several mechanisms to successfully treat mitral regurgitation:
- Reshaping and Stabilizing the Annulus: Rings reshape the mitral annulus to its normal elliptical form and size if dilated. This holds the annulus steady and prevents further enlargement.
- Improving Leaflet Coaptation: By fixing the annulus size, the rings bring the mitral leaflets closer together facilitating better apposition and coaptation during systole. This seals the valve.
- Correcting Geometry: Annular dilation distorts the geometric relationship between the annulus, leaflets and left ventricle. Rings correct this geometry to allow physiological opening and closing of the mitral leaflets.
- Reducing Tension on Chordae Tendineae: Dilated annulus pulls excessively on the chordae resulting in improper coaptation. Rings decrease this tension on the chordae and papillary muscles improving leaflet motility.
- Preventing Future Dilatation: By stabilizing the annulus, rings prevent further stretching of the ring and anular dilatation which can cause recurrence of mitral regurgitation.
Surgical Technique For Mitral Valve Annuloplasty
Annular stabilization and reshaping is commonly done as an adjunct procedure during surgical repair of the mitral valve via either an open-heart surgery or a minimally invasive approach. The steps involved are:
- Exposing the mitral valve through a sternotomy incision or ports.
- Assessing the degree of regurgitation and any pathology of the valve leaflets or chordae.
- Sizing the annulus and selecting the appropriately sized annuloplasty ring.
- Placing permanent sutures around the annulus.
- Inserting and securing the ring, reshaping the annulus to its intended form and size.
- Testing the competency of the valve by injecting fluid/air through the left atrium.
- Closing the incisions after ensuring no residual regurgitation through the valve.
Advantages Of Mitral Valve Annuloplasty
Mitral valve repair with annuloplasty rings is widely accepted as the gold standard treatment for mitral regurgitation due to its many advantages over replacement:
- Preservation of native valve anatomy and physiological function.
- Avoidance of lifelong anticoagulation therapy required with mechanical valves.
- Superior hemodynamics - repaired mitral valve mimics normal valve physiology better than a prosthesis.
- Lower risk of thrombosis, bleeding events and endocarditis compared to replacements.
- Better survival and quality of life outcomes than replacement in long term follow-up studies.
- Can be used for a variety of mitral pathologies in combination with other repair techniques like leaflet procedures.
- Reshaping stabilizes the annulus to prevent recurrent dilation and repair failure over time.
- Option of less invasive mitral valve surgery through minimally access approaches.
Limitations And Complications Of Annuloplasty Rings
While mitral valve repair with annuloplasty rings has significant advantages, it is not without risks and potential limitations:
- Still a complex open heart surgical procedure with general risks of surgery and cardiopulmonary bypass.
- Size mismatch of selected ring with patient's annulus can cause residual regurgitation or obstruction.
- Stiff rings can hinder normal dynamic function and mobility of the valve in some patients.
- Repair durability depends on the severity of underlying valve disease and techniques used.
- Failure or detachment of sutures holding the ring can cause repair failure over time.
- Recurrence of regurgitation possible if repair does not adequately address all components of valve dysfunction.
- Risks associated with minimally invasive approaches include limitation of operating space and visibility.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it