Normal mitral valve function implies that the free edge of the leaflets remains at the same level and 5 to 10 mm below the plane of the orifice during systole to ensure proper leaflet coaptation and valve competency. Leaflet prolapse (or functional type II) is a valve dysfunction in which the free edge of a leaflet overrides the plane of the mitral orifice during systole . The differential diagnoses of leaflet prolapse are illustrated in Figure 10-1 .
Anterior leaflet prolapse is commonly seen in degenerative valve disease, bacterial endocarditis, and rheumatic valvular disease. It is less commonly observed in congenital malformation, trauma, and ischemic valve disease. Anterior leaflet prolapse should be differentiated from the billowing leaflets seen in Barlow’s valve, in which the free edge of the leaflets remains below the plane of the mitral annulus . However, a leaflet prolapse may complicate the course of this disease.
Several surgical techniques have been developed to correct anterior leaflet prolapse. The choice of the appropriate technique depends upon the anatomical conditions: the extent of the prolapse (i.e., the length and number of leaflet segments involved); the degree of prolapse (i.e., the degree of overriding); and, most importantly, the lesions producing the prolapse (i.e., chordae or papillary muscle rupture or elongation). The “one lesion one technique principle” facilitates the choice between the different technical options. Correct identification of the lesions is therefore the first step in the process of valve reconstruction. We will first describe anterior leaflet prolapse caused by chordae rupture and by chordae elongation, which are the most frequent causes of prolapse, and then we will discuss the management of prolapse caused by papillary muscle rupture or elongation. The techniques for the correction of anterior leaflet prolapse caused by chordae rupture or elongation are summarized in Table 10-1 and described in the following paragraphs.
| Limited Prolapse | Extensive Prolapse | ||||
|---|---|---|---|---|---|
| Due to Chordae Rupture | Due to Chordae Elongation | ||||
| Anatomic Conditions | Prolapse area <1/4 of length | Anterior secondary chordae available | No anterior secondary chordae available | ≤10 mm | ≥10 mm |
| Techniques | Leaflet triangular resection | Anterior secondary chordae transposition | Posterior leaflet chordae transposition | Papillary muscle sliding | Chordae shortening or replacement |
| Alternative Techniques | Leaflet fixation on secondary chordae | Chordae replacement | Papillary muscle shortening | ||
LIMITED PROLAPSE
A limited prolapse, defined as a prolapse involving less than one fourth of the total length of the free edge of the anterior leaflet ( Fig. 10-2 ), can be treated by leaflet triangular resection or leaflet fixation on secondary chordae in both chordae elongation and chordae rupture ( Table 10-1 ).
Leaflet Triangular Resection
In the past we have performed leaflet triangular resection ( Fig. 10-2 ) too frequently. Our experience with this technique has illustrated that some rules should be respected to achieve a predictable and durable result. Because of its simplicity, this technique is very useful but should only be used when the prolapsed portion is small and represents less than one fifth of the length of the free margin of the anterior leaflet (a) . The result is that less than 10% of the anterior leaflet surface area is resected. The limits of the prolapsed area are identified by the adjacent non-elongated chordae. Two nerve hooks or 2-0 stay sutures are passed around them (b) . A gentle traction allows visualization of the triangle of tissue to be resected. If B measures the base of the triangle and H is its height, H should be slightly longer than B . A 5-0 suture is placed to identify the vertex of the triangle ( Fig. 10-3 ). The triangular resection is carried out with curved scissors in order to produce a slightly convex curvature of the two sides of the triangle (a) . This provides an optimal curvature to the repaired leaflet. The two edges of the leaflet are then sutured using 4-0 or 5-0 polyester sutures, depending on the thickness of the leaflets. These sutures can be everted (b) or preferably inverted (c) to provide a more regular surface of coaptation without protruding knots. In the latter case, the knots are positioned on the ventricular side of the leaflet (d, e) . Once the sutures have been completed and tied, a nerve hook should be used to detect any residual defect. If a defect is present, it is closed by an additional noninverted 5-0 suture.
Anterior leaflet resection should not involve more than 10% of the leaflet surface area.
Leaflet Fixation on Secondary Chordae
Leaflet fixation on secondary chordae ( Fig. 10-4 ) is indicated whenever a strong, at least 2 mm thick, nonelongated secondary chorda is less than 5 mm from the free edge of a well-pliable prolapsed segment (a, b) . Two 5-0 monofilament sutures are passed through the chordae, taking two thirds of its thickness, and then through the leaflet free edge at the corresponding levels (c, d) . The sutures are then tied and cut (e) . An alternative technique (f) that avoids knot protrusion implies that the same end of the 5-0 suture is passed first through the chorda and then twice through the leaflet edge (g) , and then tied with the other end so that the knot is positioned under the leaflet (h) .
When the distance between the chordae and the free edge of the leaflet is ≥ mm, a secondary chordae transposition is preferred.
EXTENSIVE PROLAPSE CAUSED BY CHORDAE RUPTURE
Depending upon anatomical conditions, anterior leaflet extensive prolapse caused by chordae rupture can be treated by (1) secondary chordae transposition to the leaflet margin, (2) chordae transposition from the posterior leaflet, or (3) chordae replacement using artificial chordae.
Anterior Leaflet Secondary Chordae Transposition
In many instances, strong secondary chordae attached to the ventricular aspect of the anterior leaflet are suitable to be transferred to the free edge of the prolapsed area ( Fig. 10-5, insets ). Several advantages favor the use of secondary chordae: native chordae are living tissues resistant to infection, they have optimal physical characteristics of pliability and elasticity, and adjustment of the length using the reference point method is particularly easy. Long-term experience (up to 25 years) has shown the excellent durability of this type of repair whenever associated with a remodeling annuloplasty, even in degenerative valvular disease. The technique is safe and effective under the following three conditions: (1) chordae attached to the papillary muscle situated underneath the prolapse are selected (avoid crossing the midline of the orifice); (2) thick and resilient secondary chordae are chosen (usually the main secondary chordae); (3) a remodeling annuloplasty ring is implanted to restore a large surface of coaptation so as to reduce the tension on both the leaflet tissue and the transposed chordae.
In chordae transposition, care must be taken not to cross other chordae or the midline of the mitral valve orifice to prevent chordae abrasion or tissue deformation.
The technique is as follows: the ventricular side of the prolapsed area is explored ( Fig. 10-5, a ). One or two secondary chordae are selected depending upon the extent of the prolapse. These selected chordae are cut 1 to 2 mm from their leaflet attachment (b) , while gentle traction is applied to avoid invaginating the leaflet tissue as a perforation may result from excess traction. The secondary chordae attached to the belly of the leaflet are usually a few millimeters longer than their marginal counterpart so that this extra length is available to secure the chordae to the leaflet edge ( Fig. 10-6, a ). The length of each detached chordae is compared to an adjacent non-elongated chordae (reference point method) (b) . At the free edge level, a mark can be made on the detached chorda using a surgical marker (c) . A 5-0 monofilament suture is placed through the whole thickness of the chorda at the appropriate level (d) and then through the leaflet edge. The upper end of this suture is then placed twice again in the same manner, thus forming a double figure-of-eight (e, f) . The knot is ideally positioned underneath the leaflet free edge (g) . Interrupted 5-0 sutures may be used instead of the double figure-of-eight configuration.
At any given stage of the procedure, the free edge of the prolapsed area should be compared with the free edge of a nonprolapsed area using nerve hooks.
The optimal number of chordae that should be transferred to the leaflet edge is based on the following principle: no portion of the free edge greater than 4 mm should be left unsupported . Whenever the number of anterior leaflet secondary chordae available is insufficient to respect this rule ( Fig. 10-7 ), a procedure combining a limited triangular resection (a, b) with chordae transposition or artificial chordae is performed ( c ).
Posterior Leaflet Chordae Transposition
Historically, this technique ( Fig. 10-8 ) comprised the transposition of a large segment of the posterior leaflet with its supporting chordae to the opposing prolapsed area (a-e) . The large quadrangular leaflet detachment implied an annular plication to restore leaflet continuity (f) . As time passed and experience grew, it was found that a narrow strip of posterior leaflet segment with its marginal chordae could be as efficient as a large segment with the advantage of not requiring a quadrangular resection of the remaining leaflet tissue.
The current simplified technique is the following ( Fig. 10-9 ): The segment of the posterior leaflet facing the prolapsed area of the anterior leaflet is identified (a) . A 3-mm-wide strip of posterior leaflet tissue along the leaflet edge is mobilized with its supporting chordae. The length of the strip is approximately equal to the length of the prolapsed area. The papillary muscle head attaching the corresponding chordae is mobilized towards the anterior leaflet (b) by splitting (inset) . The posterior leaflet strip is reattached to the free edge of the prolapsed area using 5-0 sutures (c) . The posterior leaflet is then reconstructed by closing the defect (d) . A 5-0 suture is passed at the two extremities of the resected area. Then, gentle traction on this suture (e) produces a plication of the leaflet tissue, which is secured by interrupted 5-0 sutures, thus effectively restoring leaflet continuity (f) .
Artificial Chordae
Artificial chordae consisting of different materials (such as silk, nylon, and Teflon) have been used since the early 1960s. However, it was only after the experimental work and first clinical applications by Robert Frater and colleagues, using polytetrafluoroethylene chordae, that this technique achieved widespread use in both adults and children. Although the use of living tissue is always preferable to artificial substitutes, the use of artificial chordae is indicated whenever adequate native chordae are not available ( Fig. 10-10, a ).
The main difficulty using artificial chordae is the adjustment of the length between the tip of the papillary muscle and the leaflet edge. Not only is the adjustment difficult but also the sliding characteristics of the polytetrafluoroethylene thread make it difficult to tie the knots. This difficulty explains why so many techniques have been proposed. Whatever the technique chosen, the “reference point method” serves as the guideline for the adjustment of the length of the artificial chordae. We describe here the two techniques we currently use depending upon whether the length of the chordae is adjusted at the leaflet level or at the ventricular level.
Adjustment at the Leaflet Level
A non-elongated reference chorda is pulled upward by a nerve hook or a 2-0 traction suture (b) . Its length is measured using a graduated hook. A 5-0 double-armed polytetrafluoroethylene (PTFE) suture is passed through the fibrous cuff of the tip of the papillary muscle corresponding to the prolapsed area, carefully keeping the suture 2 to 3 mm from adjacent native chordae. This suture is passed once again to achieve a figure-of-eight fixation and then tied, leaving two ends of equal length (c) . Pledgets are used only if the tip of the papillary muscle is muscular rather than fibrous.
Adjusting the length of PTFE chordae is achieved by comparative measurements using the “reference point method.”
One end of the PTFE suture is passed through the free edge of the prolapsed area (d) . Using the non-elongated chorda as a reference, a mark is made on the artificial chordae at the appropriate level. Another alternative is to use the graduated hook (e) . The other end of the PTFE suture is then passed 3 mm from the insertion site of the first end, through the free edge of the prolapsed area, taking care not to cross native chordae to avoid chordae abrasion (f) .
The two ends of the artificial chordae are passed through the free edge of the leaflet once again so that the knot can be tied on the ventricular side (g) . The first knot is tied while adjusting the length to the level of reference using either the graduating instrument or the marks (h) . A second knot is tied and saline is injected within the ventricular cavity to ensure that the supported free edge is aligned with the nonprolapsed opposing leaflet. This maneuver can be performed after the ring has been lowered into position.
The knots are then completed (i) and positioned under the leaflet by using 5-0 suture (j) . Several PTFE chordae may be necessary to support the free edge of the prolapsed leaflet. The optimal interval between them is 3 to 4 mm.
Adjustment at the Ventricular Level
In this technique ( Fig. 10-11 ), one single pledgetted PTFE 5-0 suture is passed first through the tip of the papillary muscle corresponding to the prolapsed area, then through the leaflet edge, and then again through the papillary muscle so that a loop is completed. The knot is positioned on the papillary muscle. Another loop is completed. The sutures are tied, adjusting their length while exerting appropriate tension on the free edge.
