Mitral Valve Repair

In patients with rheumatic valve disease, it is critical to evaluate the aortic and tricuspid valves as associated lesions are very common.The marginal chordae are fenestrated with a small triangular wedge resection or split.Post bypass TEE is critical in patients with rheumatic disease.Patch extension can be applied to both the anterior or posterior leaflet depending upon the localization and extent of the lesions.Care should be taken to leave one chordae on each side of the commissural opening.In this scenario, it is necessary to implant a remodeling prosthetic ring to prevent post-commissurotomy regurgitation.Commissurotomy is started along this groove while leaving a 5mm tissue ridge from the annulus and is directed toward the center of the orifice.Locating the site of the commissure can be difficult in the presence of advanced rheumatic lesions.Most patients present with type IIIa dysfunction.The presence and the severity of valvular calcification should be assessed.Residual mean transvalvular gradient less than 5 mmHg is acceptable, but gradients greater than 8 mmHg indicates the need for a second exploration and valve replacement.It is not advisable to increase the height to more than 2 cm as that may create a curtain effect with a risk of mitral stenosis.In patients with commissural fusion, mitral commissurotomy is performed to increase the opening of the mitral valve.When fused chordae beneath the commissure are identified, they should be fenestrated using a triangular wedge resection.Typically a ring 30 or 32 mm is selected in female whereas a ring 32 or 34 mm is selected in male.In patients with mitral stenosis and annular dilatation, an isolated commissurotomy may result in mitral regurgitation.It is also important to assess the mobility of the anterior leaflet and the extent of subvalvular lesions as they both predict the feasibility of valve reconstruction.The latter procedure further enhances the commissural opening.Finally, mitral valve area and transvalvular gradient should be calculated.Marginal chordae can also be resected provided that the free margin is supported every 4mm along its entire length.

Occasionally the marginal chordae can be thickened and elongated.Subvalvular lesions are addressed by the resection of thickened secondary chordae.Leaflet thickening/retraction is best treated with patch extension using Glutaraldehyde-treated autologous pericardium.The insertion of smaller rings is associated with the risk of mitral stenosis and early repair failure.Commissural fusion is usually more intense at the postero-medial commissure than the antero-lateral commissure.In patients with anterior leaflet prolapse, the responsible lesion is either a posterior or a lateral displacement of the paramedial chordae.The principle objectives of the patch extension are to increase leaflet mobility, to enhance the surface of coaptation and to allow the implantation of a larger prosthetic ring.Calcified nodules in the commissural area should be excised.The height of the reconstructed posterior leaflet should be between 15 to 20 mm.A mild degree of mitral regurgitation does not require a second look provided that a large surface of coaptation has been created.In patients with mitral regurgitation and type II dysfunction, minor prolapse of the anterior leaflet should be identified and corrected with chordae repositioning.A careful valve analysis should be performed to determine the mechanism of mitral regurgitation.The corresponding papillary muscle should also be split.The association of a restricted posterior leaflet motion (type IIIa dysfunction) with a prolapse of the anterior leaflet (type II-A2 dysfunction) is very characteristic.After the exposure of the mitral valve, the surgeon should perform a detailed valvular analysis and make a full inventory of the lesions: commissural fusion, leaflet thickening/retraction, chordae fusion and shortening, and annular dilatation.

Following the patch extension, a ring is selected which is one or two size bigger than the size of the measured anterior leaflet.Following valvular analysis, the appropriate reconstructive techniques are selected according to Carpentier's one-lesion- one-technique principle.Prior to cardiopulmonary bypass, an intraoperative transesophageal echocardiography is performed in all patients.Following the detachment of the posterior leaflet and the resection of secondary chordae, a diamond-shaped patch of appropriate size is tailored and implanted using a running suture technique.Traction on the main chordae of the anterior leaflet opposite to the commissure is key to identify the commissural groove.

Post-cardiopulmonary bypass, transesophageal echocardiography is used to assess: 1) the deairing of the cardiac chambers, 2) the quality of repair, 3) the transvalvular gradient and the orifice area, and 4) the right and left ventricular functions.

These complex and multiple lesions raise the question of the feasibility of valve reconstruction which ultimately depends upon two factors: 1) the surface area and pliability of the anterior leaflet and   2) the extent of subvalvular lesions.The incision should be extended to the papillary muscle leaving a greater thickness on the anterior leaflet side than on the posterior leaflet side.In practice, patch extension of the posterior leaflet is performed more commonly.