Commissural Fusion: Commissurotomy

Commissural fusion is treated by commissurotomy ( Fig. 13-3 ). To avoid commissural leakage, the technique should preserve a 5 mm long segment of valvular tissue near the annulus equivalent to the commissural leaflet. The main difficulty in performing a commissurotomy is the identification of a commissural line—the delineation between the anterior and the posterior leaflets. This is relatively easy in grade I and grade II commissural fusion but more difficult whenever the line of commissurotomy is not apparent, as in grade III fusion. In this case, traction on the main chordae of the anterior leaflet opposite to the commissure creates a furrow, which delineates the limit between the anterior and the posterior leaflets (a) . Using a knife with a sharp triangular blade, the incision begins 5 mm from the annulus and proceeds towards the mitral valve orifice (b) . At 5 mm from the orifice, the incision is interrupted. The commissural chordae are then identified and exposed with a nerve hook or a right angle clamp passed around the corresponding papillary muscle (c) . The incision is then completed, leaving at least one chordae on each margin of the commissural opening ( d ). The corresponding papillary muscle is split, leaving a little more thickness on the anterior leaflet side than on the posterior leaflet side. The splitting of the papillary muscle is extended downward until a subcommissural orifice is created. This orifice should be large enough to admit the extremity of a cardiotomy sucker (e) . Whenever possible, the splitting of chordae or papillary muscle is completed by a “fenestration,” ^*

* See Glossary .

Subvalvular Lesions: Chordae Resection and Fenestration

Leaflet mobilization is completed by resecting thickened secondary chordae and by splitting or “fenestrating” fused marginal chordae ( Fig. 13-4, a ). The secondary chordae to be resected are identified with a nerve hook (b) . Their attachment to the papillary muscle is cut first. The attachment to the leaflet is then exposed by gentle traction and also cut (inset) . During this maneuver, care should be taken to avoid cutting an adjacent marginal chordae inadvertently and to avoid excess traction, which may lead to leaflet perforation. If a defect is made in the leaflet tissue, it is closed by direct suture or occasionally a small piece of autologous pericardium. All thickened chordae can be resected without hesitation provided that at least one marginal chordae is preserved every 4 mm along the leaflet free edge. Whenever the distance between two marginal chordae is greater than 4 mm, a secondary chordae of appropriate length should be transposed to secure the free edge of the leaflet. Fused marginal chordae participating in the subvalvular obstruction are not cut, but “fenestrated” by removing a triangular piece of fibrous tissue and splitting the corresponding papillary muscle.

Annular Deformation: Ring Annuloplasty

In mitral valve stenosis , a ring annuloplasty is not necessary whenever the ventricular function is preserved, the atrial enlargement is moderate, and the mitral orifice has a normal ovoid kidney shape with no significant annular dilatation ( Fig. 13-5, a ). In this condition, a commissurotomy usually corrects the mitral stenosis without producing regurgitation (b, c) . In contrast, in the setting of annular dilatation (d) , a commissurotomy may lead to further annular dilatation and lack of leaflet coaptation (e) . This mechanism explains, at least in part, the mitral valve regurgitation sometimes seen after a successful commissurotomy. A remodeling ring annuloplasty is therefore mandatory in mitral valve stenosis with a dilated annulus and severely dilated left atrium to avoid postcommissurotomy regurgitation (f) . A “Classic ring” specifically designed for rheumatic valvular disease is preferred but a Physio ring can also be used if the height of the anterior leaflet fits that of the sizer preselected according to the intercommissural distance. Rings smaller size than 30 mm in females and 32 mm in males should be avoided.