Eur J Cardiothorac Surg 2006;29:1026-1029
© 2006 Elsevier Science NL
The ‘Valve Racket’: a new and different concept of atrioventricular valve repair
José M. Bernal
a
,
*
,
Iván García
a
,
Dieter Morales
a
,
Carmen Diago
b
,
Blanca Ruiz
c
,
Fernando Val
d
,
José L. Ojeda
e
,
José M. Revuelta
a
a Department of Cardiovascular Surgery, Hospital Universitario Valdecilla, E-39008 Santander, Spain
b Department of Anesthesiology, Hospital Universitario Valdecilla, Spain
c Department of Cardiology, Hospital Universitario Valdecilla, Spain
d Department of Pathology, Hospital Universitario Valdecilla, Spain
e Department of Anatomy and Cellular Biology, Universidad de Cantabria, Santander, Spain
Received 7 November 2005;
received in revised form 15 February 2006;
accepted 22 February 2006.
* Corresponding author. Tel.: +34 942 202536; fax: +34 942 203535. (Email: ccabmj{at}humv.es).
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Abstract
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Objective: Mitral regurgitation due to prolapse of the mitral leaflets frequently compromises annuloplasty repair procedures. We present a new annuloplasty ring that overcomes this difficulty, preventing displacement of the leaflets into the atrium. Methods: The ‘Valve Racket’ is a prosthetic ring transformed into a racket by means of handmade mesh using expanded polytetrafluoroethylene (ePTFE Gore-Tex). After transection of the marginal chordae tendineae, five sheep had the new racket implanted in the mitral (n
= 3) and in the tricuspid position (n
= 2). The surviving sheep underwent postoperative evaluation. Results: After six months of operation, a standard transthoracic study showed competent valves without significant gradients and without residual valve regurgitation. The ring appeared encapsulated by a uniform fibrous tissue but the threads showed a completely denuded surface except in the zone proximal to the ring. Thrombi or calcification deposits in the ring, racket's mesh, or cardiac chamber were not observed. Conclusion: This initial experience confirmed the efficacy and simplicity of the technique.
Key Words: Mitral valve repair • Tricuspid valve • Animal model • Heart valve
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1. Introduction
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After aortic valve stenosis, mitral regurgitation is the most common valve disease requiring surgical treatment. Mitral valve repair offers several important advantages compared with valve replacement, including lower operative mortality, better long-term survival, and lower risk of valve-related complications. Chronic ischemic or degenerative mitral regurgitation may result from progressive annulus dilatation and mitral valve prolapse. Several annuloplasty rings following the principles originally described by Carpentier [1] have been advocated for mitral valve repair. However, the feasibility of valve repair is highly dependent on the extent of leaflet pathology. Edge-to-edge approximation of the mitral valve leaflets (Alfieri procedure) [2] has contributed to increase the possibilities of mitral valve repair. Herein we are reporting the ‘Valve Racket,’ a new and different concept of atrioventricular valve repair that prevents slipping of one or both leaflets into the atrium, taking advantage of the physiologic rationale of ring annuloplasty and the mechanical anchoring effect of leaflet approximation.
This experimental study evaluates the short-term results obtained by implanting in mitral and tricuspid position the ‘Valve Racket’ in a sheep model in terms of: (a) feasibility of the new annuloplasty ring to prevent mechanically the prolapse of leaflets into the atrium, and (b) innocuousness of the racket-type mesh for the correct atrioventricular blood flow.
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2. Technique
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All animals used in this study received human care in compliance with the ‘European Convention on Animal Care’ and the ‘Principles of Laboratory Animal Care’ formulated by the Institutional Animal Care and Use Committee of the University of Cantabria.
Five sheep 6 months old weighing 20 kg (range 18–23 kg) were used for this study. The ‘Valve Racket’ was implanted in the mitral position in three animals and in the tricuspid position in two. The recipients were given no food for 48 h before operation. Anesthetic, intraoperative, and postoperative management did not vary than that previously described [3–5] but antibiotic prophylaxis with cefazoline, 1 g, was given intramuscularly every 24 h for 7 days.
The ‘Valve Racket’ (Fig. 1
) consisted of complete and preformed annuloplasty ring of 19-mm, in which a handmade racket-type mesh was constructed using expanded polytetrafluoroethylene (ePTFE Gore-Tex, 4/0) (patent pending). The frame was allowed to lie slightly untightened to capture the inertia derived from contact of the leaflets with the mesh during systole.
The heart was exposed through a left (mitral) or right (tricuspid) anterolateral thoracotomy in the fourth intercostal space. The right femoral artery was cannulated for arterial perfusion, and the right atrium or the cava veins were cannulated for venous return. During the cardiopulmonary bypass, the heart was maintained beating under normothermic conditions, and an atriotomy parallel to the atrioventricular sulcus was performed. A marginal chordae tendinae in the middle point of the anterior mitral or tricuspid leaflet was transected. The marginal chordae sectioned both in the anterior leaflet of the mitral valve and in the anterior leaflet of the tricuspid valve was a primary chordae attached to the free leaflet margin. The ‘Valve Racket’ was implanted in the mitral or tricuspid position following a standard procedure for the implantation of a prosthetic ring, using several 4-0 polypropylene suture. The atriotomy was repaired, and the animal was separated from cardiopulmonary bypass. When the animal was standing, the orotracheal tube and the thoracic drain were removed. After operation, the animals were maintained in a heated postoperative recovery room for 24 h. Postoperative analgesia consisted of butorphanolol tartrate, 0.5 mg intramuscularly, every 8 h for the first 3 days. The condition of the animals was evaluated daily by us and by a veterinarian.
After 6 months of operation (range 170–205 days) in sinus rhythm and without anticoagulation, the surviving animals were transferred to the research unit. A standard transthoracic echocardiographic study with continuous electrocardiographic monitorization was performed. All animals showed functionally competent valves without significant gradients and without residual mitral regurgitation. The plane of valve closure, the prosthetic ring, and the racket's mesh were detectable in parasternal short-axis view. In the four-chamber projection echocardiography, contact between anterior and posterior mitral leaflets and the valve racket was observed (Fig. 2
). After completing the echocardiography and echocardiographic video recording, a dose of heparin sodium, 3 mg/kg, was administered, the animals were killed with a single dose of sodium thiopental, 30 mg/kg, and the heart was explanted. At gross inspection, the ‘Valve Racket’ was anchored in the native mitral or tricuspid ring. The threads of the racket's mesh were apparently normal and had not lost their original properties. The ring was covered by a whitish fibrous tissue (Figs. 3 and 4
). Thrombi or signs of other anomalies were not observed. In the radiographic study, calcifications were not seen. Scanning microscopic examination revealed coverage of the prosthetic ring by endothelial cells. The threads showed a completely denuded surface except in the zone proximal to the ring where they were also covered by endothelial cells (Fig. 5
). The atrial surface of the leaflets showed a normal appearance. Examination with a light microscopy confirmed that the ring appeared encapsulated by a uniform fibrous tissue. Thrombi deposits in the ring, racket's mesh, or cardiac chambers were not observed. The atrial and ventricular aspects of the leaflets showed no abnormalities both in the mitral and tricuspid valves (Fig. 6
). This finding indicates preservation of the tissue integrity without evidence of calcium or iron deposits, fibrosis, or cellular infiltration.
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Fig. 2. Echocardiographic view of the ‘Valve Racket’ implanted in the mitral position in the four-chamber projection. (A) The mitral valve and the leaflets are completely closed, with an arrow pointing on the mesh of the racket. (B) In the immediately neck image, the anterior mitral leaflet (thin arrow) is separated from the mesh of the ‘Valve Racket’ (thick arrow).
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Fig. 5. Ultrastructure of the explanted heart showing the prosthetic annuloplasty ring covered by endothelium and a completely denuded mesh. A knot of the suture is observed.
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Fig. 6. Microscopic view of the atrial aspect of the anterior leaflet of the mitral valve shows integrity of its structure with absence of calcium deposits or inflammatory cell.
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3. Discussion
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The ‘Valve Racket’ is an innovative device for its application in valve surgery designed to combine in a single option physiologic repair of annular dilatation and mechanical repair of leaflets prolapsed into the atrium by means of the protecting mesh. Implantation of the device does not require a previous experience or a learning curve. The racket is implanted following the same surgical technique than for any other annuloplasty ring. This novel technique is both hypothetically sound and highly practical in the setting of mitral valve regurgitation resulting from anterior or bileaflet prolapse.
In the sheep model of acute mitral and tricuspid valve regurgitation, the technique of the ‘Valve Racket’ was shown to be effective and not harmful after a follow-up of 6 months, encouraging us to continue further research using this technique. The echocardiographic study showed contact between valve leaflets and the mesh of PTFE sutures but during the 6 months that the ‘Valve Racket’ was implanted contact lesions were not observed, probably due to soft sliding of the leaflets on the non-stretched texture the mesh. This experimental model, however, does not reproduce the lesions found in atrioventricular regurgitation, particularly mitral valve regurgitation, in humans. In patients with mitral insufficiency in the setting of Barlow's disease, all the components of the mitral valve apparatus are involved by a myxomatous degeneration, which eventually leads to generalized bileaflet prolapse. The free edges of these myxomatous valves are often elongated and irregular, with an increased number of clefts and multiple regurgigant jets. In this context, in which a conventional mitral repair is sometimes associated with suboptimal results, the racket's mesh would prevent billowing of redundant myxomatous leaflet tissue into the left atrium.
The present findings should be interpreted according to inherent limitations of a preliminary experimental study without control experiments and the fact that testing of the device is insufficient to support clinical application in valve surgery. It was not possible to include a control group of severe mitral/tricuspid valve regurgitation because attempts made in two animals were unsuccessful; the two animals died because of acute pulmonary edema in one and massive bleeding due to inability to close the atriotomy incision in the other. Moreover, studies reported in literature have been performed in the sheep model of ischemic mitral regurgitation after occlusion of a marginal branch [6], or after splitting a second order chordae tendineae by surgical [7] or endoscopic procedures [8], or establishing a small defect in the valvular leaflet [9]. In these models, the degree of regurgitation is not sufficiently to reproduce prolapse of the leaflets and to assess the results of a repair technique.
Some aspects should be studied before any potential clinical application of the new device. The most adequate configuration of the mesh should be determined which besides preventing prolapse of the leaflets, would not disrupt the normal flow when the blood is pumped into the ventricle. The ‘Valve Racket’ can be constructed on any type of annuloplasty ring. On the other hand, both the material used to make the racket (polypropilene, ePTFE, NitinolR, etc.) and the configuration of the mesh may vary. The racket of this prototype was composed of ePTFE, a proven suitable material in valve surgery [5] and in other cardiac procedures but a potential risk of growth of host tissue (pannus). On the other hand, long-term studies are needed to assess the development of contact lesions between atrial aspects of the valve leaflets and the racket's mesh. Despite the inherent limitations of a preliminary experimental study, our experience indicates that the ‘Valve Racket’ offers a promising physiomechanical approach for definitive atrioventricular valve repair. Obviously, long-term studies are mandatory to determine the efficacy of this procedure.
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Acknowledgments
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We thank Marta Pulido, MD, for editing the manuscript and editorial assistance.
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References
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Abstract
1. Introduction
