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Publication:

Surgical Technology International XV - Cardiovascular Surgery

Article title:

Advanced Technologies for Cardiac Valvular Replacement, Transcatheter Innovations and Reconstructive Surgery

Contents:

 

 

 

 

 

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1. Article Information, Introduction, Background

2. Current Bioprostheses

3. Mechanical Prostheses

4. Transcatheter Heart Valve Therapies, Aortic Valve Replacement

5. Mitral Valve Reconstruction

6. Annuloplasty Prostheses For Valvular Reconstructive Surgery

7. Technological Advances, Clinical Performance, Summary of Experience

8. Indications for Prostheses Choice, Conclusion

9. References

 

 

ANNULOPLASTY PROSTHESES FOR VALVULAR RECONSTRUCTIVE SURGERY

 

 

The techniques of mitral valve reconstruction have been well established, but there remains controversy regarding the types of annuloplasty rings. The available annuloplasty rings are rigid, flexible, complete, partial, and semi-rigid/flexible. Several objectives exist for annuloplasty, namely remodeling of the length and shape of the dilated annulus, prevention of dilatation of the annulus, and support for the potentially fragile area after partial-leaflet resection. Annuloplasty rings may have the potential for maintaining the anatomical and physiological characteristics of the mitral annulus (see Table IV).

The Carpentier-Edwards Classic annuloplasty rings (Edwards Lifesciences, Irvine, CA, USA) are remodeling rigid rings designed specifically for mitral and tricuspid annular reconstructive surgery (Figs. 80a & 80b). The kidney-shaped mitral ring remodels the annulus by altering the anteroposterior and transverse diameters of a normal mitral valve for optimal hemodynamic performance. The oval tricuspid ring conforms to the configuration of the normal tricuspid orifice, and has an opening in the anteroseptal commissure that avoids sutures in the area of the Bundle of His. The rings are formulated from titanium alloy, with the sewing ring margin composed of a layer of silicone rubber covered with a polyester knit fabric.

The Carpentier-Edwards Physio annuloplasty ring (Edwards Lifesciences, Irvine, CA, USA) is a remodeling, semi-flexible annuloplasty ring (Fig. 81). Remodeling preserves a natural 3:4 ratio between the anteroposterior diameter and transverse diameter during systole. The ring restores the anatomical size and shape to provide an optimal orifice area. The progressive posterior flexibility allows for physiologic contractility of the mitral valve annulus during systole. The anterior saddle shape adapts to the aortic root and conforms to the annulus anterior-fibrous segment. The ring is fabricated with layers of Elgiloy™ and plastic strips, with a sewing-line margin that consists of a layer of silicone rubber covered by a polyester knit fabric.

The Cosgrove-Edwards annuloplasty system (Edwards Lifesciences, Irvine, CA, USA) is a non-remodeling, open flexible ring (Fig. 82). The template of the annuloplasty system provides a measured plication of the annulus. The “C” shape of the flexible band allows for the anterior portion of the mitral annulus to be preserved and function naturally. The flexible band adapts to the 3-D contour of the annulus, which provides support against dilatation. The ring incorporates barium sulfate impregnated silicone rubber covered by a polyester velour cloth.

The Carpentier-McCarthy-Adams IMR ETlogix annuloplasty ring (Edwards Lifesciences, Irvine, CA, USA) is the first asymmetric ring designed to treat asymmetric dilatation (Fig. 83). The general annuloplasty rings and bands are designed for symmetric dilatation. The IMR ETlogix annuloplasty ring corrects for the valvular insufficiency associated with Type IIIb mitral regurgitation. The device decreases the AP distance and increases leaflet coaptation. The asymmetric 3-D annuloplasty ring provides reduction with the P2-P3 curvature design and compensates for the tethered P3 segment. The increased sewing margin in the P2-P3 region, marked with suture, is designed to accommodate a double-suture row.

The Edwards GeoForm annuloplasty ring (Edwards Lifesciences, Irvine, CA, USA) is geometrically designed to restore leaflet coaptation and reduce mitral regurgitation caused by enlargement of the left ventricle (Fig. 84). Remodeling of the mitral annulus with the GeoForm reforms the shape and function of the left ventricle, which aims to halt the cycle of ventricular enlargement and increases mitral regurgitation. The GeoForm ring significantly reduces the AP diameter by bringing the posterior annulus inward to counteract the outward pull of the enlarged left ventricle. As a consequence, it raises the mitral valve apparatus to counteract the downward pull of the enlarged left ventricle.

The Edwards MC3 annuloplasty system (Edwards Lifesciences, Irvine, CA, USA) is a 3-D ring designed for tricuspid valve repair; it is the first anatomically correct, 3-D ring. This anatomically correct design conforms to the 3-D tricuspid orifice and minimizes stress at the time of implantation (Fig. 85). The progressive flexibility of the ring is created from a unique processing of the titanium band. The ring is implanted with the Edwards Lanyard system, which allows visual orientation of ring placement and stabilizes the ring during suturing. The Edwards MC3 ring is an advancement of the Carpentier-Edwards tricuspid annuloplasty ring with the 3-D aspect, whereas both rings allow for non-suturing in the area of the Bundle of His.

The Medtronic-Duran flexible annuloplasty ring (Medtronic, Minneapolis, MN, USA), has been available for 25 years; it is a radio-opaque ring (Fig. 86). The ring provides the opportunity for the annulus to decrease during systole. This flexible ring is an option to a rigid ring in reconstruction for degenerative disease.
The Medtronic-Duran flexible annuloplasty band (Medtronic, Minneapolis, MN, USA) is a partial flexible device that supports reconstruction when the primary pathologic findings incorporate dilatation of the posterior annulus (Fig. 87). The Duran band extends beyond the trigones to provide secure suturing to the trigones. The band also can be used for tricuspid annuloplasty with protection of the conduction system.

The Medtronic Colvin-Galloway Future™ Band (Medtronic Inc., Minneapolis, MN, USA) is a low-profile, semi-rigid partial band composed of an inner core of a proprietary metal alloy that possesses a combination of high strength and durability (Fig. 88). The band offers stiffness to provide remodeling yet flexibility to allow movement of the mitral annulus during the cardiac cycle, due to this metal alloy core. The band also has anchoring eyelets that align with the annular trigones for ease of attachment. The CG Future annuloplasty system remodels the annulus to maintain apposition of the anterior and posterior leaflets.
The St. Jude Medical Seguin annuloplasty ring (St. Jude Medical, Inc., St. Paul, MN, USA) is made of a solid, one-piece core that consists of ultra-high weight polyethylene thicker in the anterior portion and thinner in the posterior portion to enhance flexibility (Fig. 89).

The St. Jude Medical Tailor annuloplasty ring (St. Jude Medical, Inc., St. Paul, MN, USA) is a unique annuloplasty ring that supports multiple repair options (Fig. 90). The ring is fully flexible to accommodate the natural movement of the annulus, and can be cut anywhere within the inter-trigonal area to create a customized C-ring. The ring is suitable for both mitral and tricuspid valve repair, and provides the opportunity for a complete or partial annuloplasty. The band (or C-ring) can be provided separately

The St. Jude Medical Rigid Saddle annuloplasty ring (St. Jude Medical, Inc., St. Paul, MN, USA) is uniquely designed to restore and maintain the natural saddle shape of the mitral valve annulus and the natural 3-D shape of the valve leaflets (Fig. 91).

The Sorin-CarboMedics Annulo Flo annuloplasty ring (Sorin-Cabomedics, Austin, TX, USA) is a rigid remodelling annuloplasty ring (Fig. 92). The titanium-stiffening ring ensures annulus remodeling and allows radiographic analysis. Orientation markers are provided for implant placement.

The Sorin-CarboMedics Annulo Flex annuloplasty ring (Sorin-CarboMedics, Austin, TX, USA) provides the opportunity for a partial or complete annuloplasty system (Fig. 93). Removal of the anterior portion converts the prosthesis from a complete to partial ring; two suture cut points optimize conversion to a partial ring. The full flexibility provides 3-D compliance that mirrors natural valve dynamics. The barium impregnated silicon provides radiographic visualization.

The Sorin Sovering™ annuloplasty rings (Sorin Biomedica, Saluggia, Italy) are flexible annuloplasty rings designed to allow the natural 3-D motion of the mitral (one closed ring and one open band) and tricuspid annuli (one open band) (Figs. 94a, 94b, 94c, 94d). The radiopaque silicone core is barium impregnated and is covered by knitted PET fabric, coated with Carbofilm™. The Sovering Miniband has the same design characteristics. The Sovering mitral MiniBand is shorter than any other band, it has been designed for over-reduction of posterior mitral valve segment.

The Sorin Memo 3-D annuloplasty ring (Sorin Biomedica, Saluggia, Italy) is an innovative annuloplasty ring which combines positive features of both flexible and rigid ring models (Fig. 95). The patented cell-structure design is capable of mimicking the physiologic 3-D motion of the native mitral annulus and accommodating the anatomical saddle shape while remodelling the mitral annulus and ensuring the leaflet cooptation during systole. The shape memory alloy core is aimed at restoring the natural systolic 3:4 diameter ratio. The Memo 3-D also includes the Sorin Group's exclusive Carbofilm™ coating for enhanced hemo-biocompatibility.

The Genesee Sculptor annuloplasty ring (Genesee Biomedical, Inc., Denver, CO, USA) is a semi-flexible, adjustable annular ring for mitral valve reconstruction (Fig. 96). The Sculptor ring provides re-establishment of the natural geometric and flexibility of the annulus. The anterior portion of the ring contains a curved, metal stiffener, which conforms to the shape of the anterior portion of the annulus to maintain the inter-trigonal distance during implantation and long term. The posterior portion of the ring is flexible to conform to the changes in annular shape and size during the cardiac cycle. Color-coded drawstrings allow any, or all, of the four adjustable segments of the posterior portion of the ring to be shortened, which allows for “fine-tuning” of the repair in the case of mild commissural leaks.

The Koehler MRS (Koehler, Bellshill, Scotland) is an open, flexible annuloplasty ring made of knitted PTFE that contains a radio-opaque, barium-impreg- nated silicon marker (Fig. 97). The sizer measures the surface area of outstretched anterior leaflet and predicts the MRS needed to advance the posterior leaflet, with or without resection, to coapt with the anterior leaflet to produce competence. The system indicates where the commissural sutures should be placed. The sizer area indicates the valve orifice area post-repair. In the case of triangular resection of the anterior leaflet, the surgeon chooses the sizer equal to the area of the reconstructed leaflet.

The Jostra fully flexible annuloplasty ring (Jostra Medizintechnik AG, Hechinger Strabe, Germany) is an adjustable ring for reconstruction of insufficient or dilated mitral or tricuspid valves (Fig. 98). The fully flexible ring allows the valve annulus to maintain both annular shape and motion. The ring is composed solely of PTFE and a polyester suture. The inter-trigonal segment of the ring is not adjustable. Each side of the ring can be adjusted individually; the ring can be adjusted after implantation.

The Jostra Rigid annuloplasty rings (Jostra Medizintechnik AG, Hechinger Strabe, Germany) are rigid fabric-reinforced rings, formulations for both mitral and tricuspid positions (Fig. 99a & 99b). The ring has four layers over a core of rigid titanium wire covered with a highly flexible PTFE tube, polyester knit fabric, and thin PTFE tubing.

The Jostra La Pitié annuloplasty ring (Jostra Medizintechnik AG, Hechinger Strabe, Germany) is a completely flexible, fabric-reinforced annuloplasty ring for reconstruction of insufficient or dilated mitral or tricuspid valves (Fig. 100). The ring affords the opportunity for annular shape and motion. The core of the ring is a highly flexible PTFE, round-shaped material covered with a polyester knit fabric and thin PTFE tubing.

The ATS Simulus annuloplasty ring/band (ATS Medical, Inc., Minneapolis, MN, USA) are flexible devices for mitral valve repairs (Fig. 101). Braided polyester material offers low resistance for easy needle penetration while allowing the needle to be placed anywhere along the width of the material. The controlled elasticity of the material discourages “bunching” during suturing. An innovative spoked-ring holder is provided for both the ring and band, which is released by cutting one suture.

The Shelhigh BioRing (Shelhigh, Inc., Milburn, NJ, USA) consists of a flexible C-shaped ring made of polyester material with a bridge of pericardium between the edges of the ‘C’ (Fig. 102). The fabric ring and bridge are covered with the “No-React®” process bovine pericardium, which forms a smooth layer of biocompatible material eliminating the need for autogenous pseudointima lining. Rough fabric material surfaces are known to cause hemolysis, especially when the systolic regurgitant jet hits a bare fabric material and they can also enhance thromboembolic phenomenon. As the bridge is devoid of fabric material and is delineated by green sutures, if a C-shaped ring is desired, the surgeon can cut the bridge portion of the BioRing between the two green sutures.

The Medtronic Simplici-T annuloplasty system (Medtronic, I,c., Minneapolis, MN, USA) consists of a band and holder. (Fig 103), serving to restore and support the annular shape and prevent further dilatation of mitral and tricuspid valves. The band is sutured along the annulus after the leaflets and subvalvular anatomy have been repa-ired.Unlike other annuloplasty pro- ducts, the Simplici-T system does not require the use of sizers.

The Adiam polyurethane mechanical (flexible) prosthesis (Adiam Life Science, Bernhard-Hahn, Germany) is an experimental prosthesis-in-development. The prosthesis is formulated by a specific polyurethane composition. The prosthesis-type is formulated as a trileaflet aortic prosthesis and bileaflet mitral prosthesis. The prostheses are totally formulated, inclusive of the sewing cuff, of polyurethane. The chemical composition of the polyurethane is formulated to support mitigation of calcium and prevent prosthesis degeneration.
The Sorin-CarboMedics polymer mechanical (flexible) prosthesis (Sorin-CarboMedics, Austin, TX, USA) is an experimental prosthesis-in-development (Fig. 104). Sorin-CarboMedics has developed a proprietary tear-resistant polymer similar to polyetherurethane urea (PEU) alternatives, including polycarbonateurethane (PCU) and polysiliconeurethane (PSU).
CarboMedics’ experience with a prototype polymer valve design suggested that valve mineralization is associated primarily with adherent thrombus rather than leaflet material. Surface modification of the prototype PEU valve with either of two different non-thrombogenic ligands virtually eliminated leaflet thrombus accumulation and mineralization, which implied that any material or material treatment that reduces accumulation of thrombus upon polymer valve leaflets should inhibit leaflet mineralization.
Developmental efforts at Sorin-CarboMedics have been driven by the belief that a prosthetic polymer valve, fabricated of a durable polymeric material and surface treated with a non-thrombogenic reagent, provides durability greater than that offered by current clinical tissue valves, yet may not require chronic patient anticoagulation as do mechanical valves.
The polymer developed by Sorin-CarboMedics has demonstrated that constitutive modeling and finite element analysis predicts polymer will have durability beyond a 20-year clinical valve lifetime in an appropriate design.
An acceptable design must minimize leaflet stresses and incorporate appropriate hemodynamics, while maintaining fatigue resistance and exploiting material surface chemistry. Design features that minimize leaflet stresses must not result in valve thrombosis. The ultimate design of the valve is a formidable challenge but must perform adequately in all aspects (fatigue resistance, durability, thrombosis resistance, and hemodynamics).