Mitral Valve Replacement with Total Chordal Preservation: The Eversion Technique

The preservation of the subvalvular apparatus during mitral valve replacement is necessary to maintain the geometry and function of the left ventricle. Although several complete or partial chordal preservation methods have been described, some continue to preserve only the posterior chordal attachments. This is due to a fear of possible patient prosthetic valve mismatch with many well-known chordal preservation techniques. We describe a simple method of preservation of both the leaflets and chordal attachments using a simple eversion technique. In our technique, we retain all the mitral valvular and subvalvular tissue. The excised leaflet ends are everted by the valve sutures to avoid interference with the prosthetic valve leaflets.


Introduction
Mitral valve repair is the ideal surgical management for a variety of mitral valve pathological states as it provides a competent, non-obstructed valve without compromising the left ventricular function. Despite the advantages of mitral valve repair, many surgeons consider it tedious, time-consuming, and may have high failure rates in inexperienced hands. Thus a large number of patients undergo mitral valve replacement. When repair is not feasible, the preservation of left ventricular function is an important concern.
The effects of the loss of annulo-ventricular continuity and the importance of chordal preservation have been well established and proven by various studies [1,2] since the introduction of this concept in 1964 by Lillehei and colleagues [3]. A wide variety of techniques of chordal preservation have gained popularity and are now a standard procedure during Mitral Valve replacement [4,5].
Most of the methods described in the literature emphasize the preservation of posterior cusp chords. Despite the anatomical and physiological benefits of the preservation of the subvalvular structures of both valvular leaflets, many surgeons are inclined to preserve only one posterior leaflet. This inclination is due to the technical difficulties in preserving the subvalvular apparatus of both leaflets, which can prolong the operation, the risk of implanting a smaller prosthesis, and the possibility of disrupting the outflow pathway from the left ventricle as well as contact between the prosthesis and subvalvular structures.
With the recent advancements and refinements in techniques and evolution of the low profile bi-leaflet mechanical valves, various methods of total chordal preservation are being described to preserve left ventricular systolic function. The major concern is to avoid the interference of the mechanical prosthetic function by the portions of the retained subvalvular apparatus with reduced risk of left ventricular outflow tract obstruction.
We describe a simple and easily reproducible eversion technique of total chordal preservation during mitral valve replacement, which retains the entire subvalvular apparatus as well as the leaflets without ventricular outflow tract obstruction or interference by retained chordae and leaflet tissue.

Operative technique
Full median sternotomy is the usual approach to the heart. Cardiopulmonary bypass is established using the standard bicaval cannulation. The aorta is cross clamped and the heart is arrested using antegrade cold blood cardioplegia. The mitral valve is exposed through a classic left atriotomy as shown in Figure 1.

FIGURE 1: Mitral valve exposed by Left atriotomy
The mitral valve is then examined to determine if there is commissural fusion as noted in Figure 2 and

Discussion
Our eversion surgical technique is simple and easily reproducible. This technique involves T-shaped incision into the AML and multiple incisions into the PML allows for the implantation of an adequate and larger size prosthesis to minimize post-operative patient-prosthesis mismatch. The eversion of leaflets allows the anterior and posterior chordae to fall away from the disc of the prosthesis. We have to be cautious to adjust the tension on the chordae during eversion and avoid too much stress on them. The excessive stretch can lead to chordal rupture and cause entanglement or interfere with the implanted prosthetic valve's function. The method of AML preservation employed in our technique reduces the risk of the systolic anterior motion of the anterior leaflet that could otherwise cause left ventricular outflow tract obstruction. This technique thus ensures the mitral annular-papillary muscle continuity during mitral valve replacement and minimizes the potential risks, complications, and complexities of several other techniques.