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Techniques in Type II Posterior Leaflet Prolapse
Type II posterior leaflet dysfunction is the most frequent dysfunction in mitral valve regurgitation caused by degenerative valvular disease. It can also be encountered in other etiologies such as bacterial endocarditis, and even rheumatic valvular disease in young children. The prolapse usually affects P2 but can be extended to P3 and more rarely P1. It is generally due to chordae rupture and/or elongation. A special feature of this dysfunction is the important secondary lesions affecting the prolapsed area. Over time the leaflet tissue becomes distended with proliferation of pathological tissue: the P2 segment may be two to three times the normal size. The consequence is that some portion of the excess tissue should be resected to restore a more normal valve geometry, to reduce the tension on the remaining chordae, and to stop progression of the process. The tension is reduced as a consequence of Laplace's law, which states that the larger the radius of a portion of a sphere (i.e., the prolapsed leaflet) the greater the tension on its surface, and therefore on the chordae. As shown by very long-term results, this approach effectively prevents recurrent regurgitation in most cases. An additional advantage is that it is an easy and reliable technique, which does not require surgical correction at the subvalvular level .
Resection of a portion of excess leaflet tissue is preferable in posterior leaflet prolapse to reduce the tension on the remaining leaflet tissue and chordae.
Several techniques of reconstruction can be used depending upon the extent and mechanism of the leaflet prolapse ( Table 11-1 ).
TABLE 11-1
Reconstructive Techniques in Posterior Leaflet Prolapse
| Limited Prolapse | Extensive Prolapse | ||
|---|---|---|---|
| <⅓ of Free Margin of Leaflet Segment | >⅓ of Free Margin of Leaflet Segment | 1 Entire Leaflet Segment | |
| Technique | Triangular leaflet resection | Quadrangular resection and annular plication | Quadrangular resection and sliding leaflet technique |
| Alternative Techniques in Chordae Rupture | Chordae transposition or replacement | Chordae transposition or replacement | Composite technique |
| Alternative Techniques in Chordae Elongation | Chordae shortening | Chordae shortening | Composite technique |
LIMITED PROLAPSE
A limited prolapse is a prolapse involving less than one third of the free margin of a posterior leaflet segment. Whenever the prolapsed segment displays only a small amount of excess tissue and discrete secondary lesions, chordae transposition or chordae replacement are elegant solutions. Most of the time, however, excess tissue or pathological tissue makes a limited triangular resection preferable, which has the advantage of operating at the valvular level and reducing the tension on the remaining leaflet and chordae. The degree of resection depends upon the extent of the prolapse and amount of grossly abnormal tissue.
Triangular Leaflet Resection
This technique evolved from the historical McGoon's plication technique (inset) , which was efficient but had the single disadvantage of leaving a segment of pathological tissue, which could later cause fibrous proliferation or leaflet retraction. A triangular leaflet resection ( Fig. 11-1 ) avoids this drawback. It is indicated whenever the length (B) of the free margin of the prolapsed segment is limited to less than one third of the total length (A) of the leaflet segment involved (B ≤ A/3) (b) .
To perform a limited triangular resection, two 2-0 stay sutures are passed around the non-elongated chordae at the limits of the prolapsed portion of the leaflet (c) . The height (H) of the triangular resection should be slightly longer than its base (H > B) (c) . Its sides are cut slightly convex so as to preserve the curvature of the reconstructed leaflet (d) . Leaflet continuity is restored using 4-0 or 5-0 interrupted sutures (e, f) . Depending upon the thickness of the tissue, these sutures can be inverted, with the advantage that the knots are positioned on the ventricular side of the leaflet (g) . A continuous suture technique is not recommended because it impairs leaflet pliability and has the tendency to produce a purse-string effect. Once the sutures have been completed, a nerve hook is used to detect any residual defect, which would be corrected by an additional everted suture (h) . Once the leaflet continuity has been restored, the adjacent indentations are carefully examined to assess whether their edges have been separated, a potential source of leak. In this case the open indentation must be closed by two or three interrupted sutures (i) .
Transposition or Replacement of Chordae
When the prolapsed leaflet segment does not present a significant amount of excess pathological tissue, transposition of secondary or basal chordae to the free edge of the leaflet or chordae replacement are valuable alternatives. These techniques are described in Chapter 10 .
Chordae Shortening
When the prolapse is due to chordae elongation in the absence of significant excess tissue, one of the techniques of chordae shortening illustrated in Figure 10-12 can be used.
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