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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

 

 

MITRAL VALVE RECONSTRUCTION

 

The mitral valve anatomy and coronary sinus anatomy, which have been incorporated into the device development for mitral valve reconstruction are depicted in Figs, 69. and 70. respectively.

The MitraClip mitral repair system (MRS) (Evalve, Menlo Park, CA, USA) is emanated after the surgical edge-to-edge (Alfieri) technique of suturing the free edge of the anterior leaflet of the mitral valve to a corresponding portion of the posterior leaflet, which creates a permanent coaptation and functional double orifice during diastole. The technique has been shown to assure proper leaflet coaptation and effective valve closure (Fig. 71).
The system consists of a 22F steerable-guide catheter, a steerable clip-delivery catheter and an implantable clip. The clip device consists of a surgical alloy and is covered by a biocompatible polyester. Under echocardio- graphic guidance, the clip is delivered into the heart through the femoral vein, passed through the atrial septum with a transseptal puncture, and positioned in the left ventricle just below the mitral valve. The physician opens the prongs of the clip and, at end-systole, closes the clip, grasping the free edge of the leaflets at the site of regurgitation. A competent, double-orifice mitral valve, can then be achieved. The device allows for repositioning or removal of the clip. A second clip can be applied to facilitate increased valve coaptation.

The Milano endovascular edge-to-edge repair system (Edwards Lifesciences LLD, Irvine, CA, USA) is a percutaneous retrograde catheter device to deliver and secure coaptation sutures across the free edges of the anterior and posterior leaflets of the mitral valve (Fig. 72a & 72b). The procedure incorporates femoral vein access with a 14F sheath introducer and transseptal access to the left atrium and across the mitral valve to the left ventricle. The therapeutic device has a vacuum port for capture of the leaflets and stitching of the leaflet edges. The device has a fastener component for “knot” placement and cutting of the suture. The system is capable of placing more than one suture. Guidance for the device is angiography and transesophageal echocardiography (TTE) . The proposed patient population is those with mild-to-moderate ischemic mitral regurgitation or degenerative flail leaflet with no, or mild, annular dilatation. The system formulates a central repair location with a double orifice.

The Viacor PTMA (Viacor, Wilmington, MA, USA) is a coronary sinus device developed primarily for ischemic mitral regurgitation and chronic heart failure. The PTMA method is based upon placement of a novel multi-lumun delivery catheter in the coronary sinus and great cardiac vein (Fig. 73). Nitinol treatment devices are then introduced individually, or in combination, into the multi-lumen delivery catheter to reduce the anterior-posterior (AP) dimension of the mitral annulus. The method allows for precise geometric manipulation of the mitral annulus, primarily reduction of the AP diameter, and the septal-lateral dimension to optimize leaflet coaptation. The mechanism of the Viacor PTMA is to bend the mid-portion of the posterior leaflet forward, and outward counter-force on the coronary sinus near the commissures. The device affords the opportunity for late adjustment or removal of the treatment effect without adverse events. Histopathology of explanted animal hearts has demonstrated endothelialization of the device into the venous anatomy.
The Edwards Viking Endovascular coronary sinus ring (Edwards Lifesciences LLD, Irvine, CA, USA) is one of several industry initiatives to manage mitral regurgitation by coronary sinus devices (Fig. 74). The targeted population would be ischemic mitral regurgitation in conjunction with percutaneous coronary revascularization, and selected high-risk patients with dilated cardiomyopathy and advanced congestive heart failure—often in the presence of coronary artery bypass. The endovascular stent-like device is deployed into the coronary sinus and foreshortens and reshapes the mitral annulus. The device can be implanted with the support of angiography, intravascular ultrasound, and echocardiography. The device is deployed into the coronary sinus via the superior vena cava. The distal device is deployed into the great cardiac vein and proximal stent in the coronary sinus as an anchoring mechanism. The middle stent foreshortens and reshapes the coronary sinus by pushing the posterior leaflet toward the anterior leaflet, which reduces the mitral annulus AP distance or septolateral dimension reducing mitral regurgitation.

The Mitralign retrograde mitral annuloplasty (Mitralign, Salem, NH, USA) is based on the concept of suture annuloplasty duplicating this procedure via percutaneous retrograde approach. The procedure involves placement of a coronary sinus catheter on which two opposing permanent magnets are mounted and positioning the magnets behind the middle of P2 (Fig. 75a & 75b). A left ventricular catheter with a magnet tip is advanced retrograde to the underside of the mitral annulus at P2, which allows a magnetic ‘lock-up’ between the left ventricular and coronary sinus magnets. The device allows specialized ‘anchors’ that lie across the annular tissue. These anchors are plicated together and locked into position to produce 2 cm to 3 cm reduction in the posterior annular circumference, and 0.5-1.0 reduction in the septal-lateral dimension, similar to surgical annuloplasty.

The Carillon mitral contour system (Cardiac Dimensions, Kirkwood, WA, USA) is a coronary sinus device designed for effective reduction of mitral regurgitation due to functional ischemic mitral regurgitation or dilated cardiomyopathy (Fig. 76). The device is delivered percutaneously via jugular access under fluoroscopic guidance. The device consists of a shaping ribbon between distal and proximal anchors, in the great cardiac vein and coronary sinus, respectively. The device is designed to be positioned, adjusted, and gently anchored to reshape the annulus around the mitral valve to reduce mitral regurgitation.

The QuantumCor radio-frequency ablation system (QuantumCor, Lake Forest, CA, USA) is designed to shrink the annulus size of mitral valve annulus or the tricuspid valve annulus by application of radio-frequency to alter the collagen content of the annulus (Figs. 77a & 77b). The radio frequency can be applied as an open procedure and, possibly, as a percutaneous procedure. Shrinkage rate is dependent on radio-frequency temperature level and a wide spectrum of temperatures is feasible, but the time interval of application must be brief. Tendon data show a 20% shrinkage to be maximal without loss of tensile strength. Overdose of radio-frequency heat weakens collagen and leads to dilatation of the annulus.
The Coapsys device (Myocar Inc., Maple Grove, MN, USA) is a novel approach to functional mitral regurgitation designed to reduce mitral regurgitation by reducing the antero-posterior mitral annular diameter, re-approximating the anterior and posterior mitral valve leaflets (Fig. 78a & 78b). The device includes an anterior and posterior epicardial pad connected and drawn together by a transventricular chord that brings together intervening structures, such as the anterior and posterior mitral valve annulus. The Coapsys system is sought to improve ischemic cardiomyopathy by reducing the antero-posterior left ventricular size. The Coapsys trial has the device implanted off of the cardiopulmonary bypass under echocardiographic guidance. The Coapsys device reduces annular dimension, short axis diameters, and sphericity indices. The studies have shown that Coapsys provides greater left ventricular remodelling compared to standard mitral annuloplasty.

The SIS wound matrix device (Cook Biotech Inc, West Lafayette, IN, USA) is the submucosa derived from porcine small intestine. The porcine small intestine submucosa is a complex matrix of collagen, as well as other proteins and growth factors. The SIS material can serve as a scaffold for wound healing and aids in proliferation of new blood vessels. The proliferated blood vessels nourish the graft and supply vital molecules the body needs to rebuild the damaged tissue. The material prompts the body to build new tissue, inexplicably replacing the intestine-derived material. The body dismantles the material as it grows new cells. The SIS could likely support development of tissue-engineered heart valves or damaged valves from endocarditis or structural failure.

Percutaneous bioprostheses for tricuspid regurgitation (3F Therapeutics, Lake Forest, CA, USA) is the concept of ovine-stented valves in the superior vena cava and inferior vena cava. The concept confines tricuspid regurgitation volume to the right atrium (Fig. 79). The devices are developmental under preliminary assessment.