Mitral Valve Repair, Research Paper Example

Leaflet Extension and Valve Patching with Biological and Prostheic Materials

Over the past several decades there have been remarkable advances in the field of mitral valve repair (MVP).  For much of the mid-20^th century, mitral valve replacement (MVR) was the first choice of treatment for dealing with mitral valve regurgitation and other valve dysfunction. Unfortunately MVR comes with concomitant risks, including problems associated with lifelong anticoagulant use, the possibility of infection, and the need for additional surgeries to replace worn valves. This is especially problematic for younger patients, as valves may need to be replaced several times. With the advent of annuloplasty and other repair techniques, however, MVP has largely supplanted MVR as a viable and effective treatment option for mitral valve dysfunction associated with a number of pathologies. While repair techniques such as the Carpentier-Edwards ring have been in use since the 1980s, more recent techniques and materials have been applied to the repair of valve leaflets, either alone or in conjunction with annuloplasty, resuspension, or other approaches. The following paper focuses on several of the materials used for the repair of mitral valves and examines their applicability for the treatment of several significant pathologies affecting the mitral valve.

Mitral Valve Repair with Autologous Pericardium

Among the most common examples of mitral valve dysfunction is mitral regurgitation. A number of pathologies and abnormalities can cause improper coaptation of the leaflets within the mitral valve, allowing blood to flow upward into the left atrium during systole. A variety of surgical techniques using biological and prosthetic materials have been developed to help bring the leaflets into alignment or to repair perforations and other abnormalities; among the most common materials is autologous pericardium. Such material is particularly useful for patients with endocarditis, as damaged tissue can be replaced through the extension of the leaflets [16]. In many cases it is necessary to surgically excise infectious tissue before undertaking repairs to the mitral valve or surrounding support structures [10, 14]. Reconstruction of the leaflets with autologous pericardium has proven to be an effective means of restoring the shape and coaptation of the leaflets [10, 14]. Such an approach can be particularly applicable in children, where MVR would present the potential for significant complications. A 2013 case study on the use of autologous leaflet repair for endocarditis in children demonstrated the feasibility of the approach, with the study subject showing “no evidence of recurrent infection, and echocardiogram showed mitral valve competence with mild mitral regurgitation” [6].

It is not just infection or tissue damage that can undermine coaptation; other conditions such as rheumatic heart disease can lead to mitral insufficiency [19]. While infection and heart disease can cause stenosis and impeded blood flow through the mitral valve, the development of fibrous or calcified material associated with such conditions can also cause the anterior or posterior leaflets to stiffen or retract. This may not require the excision of vegetation such as that which is seen in endocarditis, it may still be useful to perform leaflet extension procedures to restore proper valve function [19]. MVP involving annuloplasty has proven insufficient in some cases to treat rheumatic valve dysfunction; as such, anterior leaflet augmentation has demonstrated viability as an adjunct course of treatment to compensate for the retraction of the surrounding support structures of the mitral valve [1].

Less common problems associated with mitral valve insufficiency or dysfunction may also benefit from the use of autologous pericardium.  Mitral Valve Aneurysm (MVA), while rarely reported, can result from complications associated with infective endocarditis of the aortic valve [20]. In a case study on a patient with MVA, a combination of aortic valve replacement and anterior leaflet resection and extension was used to positive effect [20]. In a similar case with concomitant aortic and mitral valve dysfunction, excision and resection of aortic abnormality was performed, which left am intact section of autologous material for use as a patch on the anterior mitral leaflet [14]. Where it is possible to use autologous material, the results are often positive, with normal coaptation achieved in many cases [5.]. Owing to the nature of this approach, however, there are some challenges associated with leaflet extension or valve patch using biological materials. Autologous pericardium may be treated with glutaraldehyde, which can facilitate reconstruction of the valve [2].

Mitral Valve Repair with Bovine Pericardium

In some instances where leaflet extension or other valve repairs are warranted it may not be possible to utilize autologous pericardium. Bovine pericardium has been shown to be an effective material for such procedures, and is applicable for conditions arising from a number of pathologies. Leaflet extension with bovine pericardium has been used in response to restricted leaflet motion associated with ischemic cardiomyopathy, rheumatic valve disease, and other conditions [8]. In a case study of a 36-year-old patient with non-ischemic type IIIb mitral regurgitation, posterior leaflet extension with glutaraldehyde-treated bovine pericardium produced satisfactory results [8]. Bovine pericardium is also useful for leaflet extension where infective endocarditis has damaged or destroyed valve tissue, with case studies demonstrating sufficient post-operative valve function [13]. For patients with rheumatic valve dysfunction where calcification and retraction are present, photo-oxidized bovine pericardium may present an alternative to treatment with glutaraldehyde. Photo-oxidized bovine pericardium may be less susceptible to post-intervention calcification than glutaraldehyde-treated material, thereby obviating potential complications [17].

Bovine pericardium may be especially useful in patients with significant damage from infective endocarditis. For patients with leaflet retraction associated with rheumatic valve disease there may be a greater likelihood of utilizing autologous material, while patients with endocarditis may simply not have enough viable autologous material for grafting [15]. Moreover, patients with infective endocarditis may lose a significant amount of tissue during MVP, as it is often necessary to aggressively remove infected material to avoid recurrence [15]. In such cases it may be necessary to not just extend leaflets, but to remove them entirely and replace them with biological material.  Even in such extreme instances, where the extent of damage warrants removal of one or more entire leaflets, it is possible to reconstruct the leaflets using bovine pericardium. Such aggressive approaches have proven successful in restoring proper valve function and avoiding the need for MVR [15].

Alternative Materials and Challenging Conditions

While it may be most common for surgeons to utilize autologous or bovine pericardium to repair mitral valve functions, other materials have been useful as well. Biological materials have some obvious positive attributes where valve repair is concerned, but in most cases such materials must be treated to avoid calcification and stiffening, and can lose pliability over time. Alternative materials such as polytetrafluoroethylene (PTFE) have long been used for a number of MVP techniques, and may provide better long-term results than biological materials in some cases of leaflet repair or extension.  A 2010 case study of 19 patients who underwent anterior leaflet enlargement showed promising results, with one late mortality and one reoperation [11]. The explanted PTFE patch from the reoperation was examined, and showed no signs of thickening, perforation, or loss of mobility [11]. While the scope of such a study is limited, the positive results may offer a basis for further research.

Despite the advances made in MVP in recent years, there are still some conditions which lead to mitral valve insufficiency that can be difficult to treat. Patients with severe ischemic mitral regurgitation do not always respond well to MVP, with a significant number still experiencing regurgitation after surgery [4]. For such patients it may be necessary to combine surgical revascularization, annuloplasty, and leaflet extension or reconstruction in order to restore sufficient valve function [4]. MVP has shown to be an improvement over MVR for patients with ischemic mitral regurgitation, but the long-term survival rate for such patients remains unclear [9].

Conclusion

It is clear that the development of new techniques and the application of appropriate materials have led to significant advances in the field of mitral valve repair. The available evidence shows that MVP offers significant benefits to patients with infective endocarditis, rheumatic valve disease, as most such patients demonstrate a return to proper coaptation and sufficient valve function [3, 7]. There seem to be relatively minor differences between the efficacy of autologous pericardium and bovine pericardium for leaflet repair, as both materials have demonstrated positive midterm and long-term results [7, 18]. The notable differences in the efficacy of leaflet repair and MVP are found in the pathologies affecting the mitral valve, with ischemia proving to be difficult to treat. The implications of MVP research are particularly notable for children, as the positive long-term results of MVP make it the first choice of treatment for young patients with mitral valve dysfunction [12]. Overall, leaflet repair has proven to be an effective means of restoring proper mitral valve function in patients with a variety of conditions.

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