A Novel and Versatile Tool for Mitral Valve Repair: The Memo 4D System

The Memo 4D System by LivaNova is a novel semi-rigid annuloplasty ring. Ideal for the minimally invasive approach, this ring allows neochord implantation without physical measurement or further adjustments in chordal heights, simplifying the decision process of the neochords’ length. In this video, the authors present their experience using the Memo 4D ring to repair three different types of mitral valve disease: fibroelastic deficiency (FED), Barlow’s disease, and anterior leaflet prolapse.

FED

The patient was a 55-year-old man with a history of FED who was found to have P2 chordal rupture. He presented to the authors’ institution with severe left ventricular (LV) dysfunction as well as severe mitral regurgitation. In the operating room, after exposure of the mitral valve and placement of the annular stitches, the mitral valve was tested. A prolapsing segment at P2 with an associated ruptured chord was noted. The prolapsing segment was marked and the prolapsing chord was removed. Two 5/0 polytetrafluoroethylene (PTFE) sutures were passed as figure-of-eight in the papillary head of each papillary muscle. The valve was sized and a ring was chosen based on a true ring sizing. Annular sutures were then placed through the sewing cuff of the mitral ring. It is important to make sure that the neochords are passed through the chordal window of the valve ring, as shown in the video. After the ring was lowered in final position, the holder was removed. The ultra-slim template was left in place to allow for easier securing of the annular sutures. The template was then removed, and the authors’ attention turned to the neochords.

First, the neochord sutures were passed through the free edge of the prolapsing segment. The suture was then passed through the chordal guiding system. The chordal guiding system is comprised of multiple loops along the ring, spanning the posterior leaflet. Sutures should be passed through the loop corresponding to the anatomical location of the prolapsing segment. The neochord suture was then passed again through the free edge and through the same loop of the chordal guiding system. The sutures were then tied together and subsequently cut. After the sutures are placed, tied, and cut, there is no more adjustment required. The chordal guiding system ensures proper leaflet height. The valve was then tested, and the coaptation zone was marked.

Barlow’s Disease

The patient in the second procedure shown was a 61-year-old man with a history of Barlow’s disease, severe mitral regurgitation, and resulting pulmonary edema. The preoperative transesophageal echocardiography images showed an excess of leaflet tissue as well as a ruptured P2 chord, resulting in severe mitral regurgitation.

After exposure of the mitral valve and placement of the annular stitches, the mitral valve was analyzed to determine the mechanism of regurgitation. A voluminous thickening of the leaflet due to the excess of tissue was present. The P2 segment was prolapsing with an associated ruptured chord. A new zone of coaptation was selected and marked, and the prolapsing chord was resected.

The next step, again, was the placement of 5/0 PTFE sutures into the papillary muscle heads. Due to a large prolapsing area, two neochords were placed into the head of each papillary muscle. The anterior leaflet was sized, and in this case, a size 36 ring was selected.

After sizing, the annular sutures were placed through the sewing cuff of the mitral ring. Again, it is important to make sure that the neochords are passed through the chordal window of the valve ring before lowering the ring to the annulus. As in the previous case, the neochords sutures were passed through the free edge of the prolapsing segment. The suture was then passed through the chordal guiding system. The process was repeated for all four neochords. The valve was then tested. It is important to properly fill the ventricle in order to have a physiological position of the mitral valve apparatus during the valve testing. As one can notice, a tendency of “over-correction” is a potential risk of this type of surgical strategy: if the neochordae are tied too tight, the prolapsing leaflet is lowered into the ventricle with a pseudo-prolapse of the opposite leaflet. It is very important to tie without any extra tension the neochordae.

Anterior Leaflet Prolapse

The last procedure presented was performed for a patient with an anterior leaflet prolapse due to a ruptured A2 chord. The technique for anterior leaflet prolapse repair is similar to the one explained for posterior leaflet prolapses. However, slight differences exist in the chordal placement.

In the video, one can see the valve exposed in the standard fashion. Valve analysis showed a prolapsing segment in A2/A3. After placing the annular sutures, attention was paid to the papillary muscle. The subvalvular apparatus was exposed. The two neochords were placed onto the papillary muscles in a figure-of-eight fashion.

After properly sizing the ring and after passing the annular stitches through the valve ring, the 2 chordae were retrieved, passing them through the ring’s chordal window. The ring was lowered and seated in the final position. The 2 neochords were passed through the prolapsing segment. Of note, the neochords were placed inside-out through the leaflet, and outside-in through the chordal guiding system—this was repeated. The same process was repeated with the second neochord on the other side. It is important to remember that for the anterior leaflet, the way in which the neochords are passed through the chordal guiding system is opposite of the technique used for posterior leaflet prolapse.

The neochords were then tied with 8-9 knots. It is important while tying the chordal knots not to make excessive counter-traction on the suture guiding system, which would enhance the risk of over-correction of the prolapse. Next, the blue stitch was removed, followed by the yellow, freeing the neochords. A saline test revealed no mitral regurgitation with a large area of coaptation.

Conclusion

To conclude, the Memo 4D System by LivaNova represents an alternative tool for mitral valve repair. It is faithful to the respect-rather-than-resect approach and provides an effective, standardized technique for several different mechanisms of leaflet prolapse. It reduces cross-clamping time and has a rapid learning curve, which makes it a comfortable tool, even in the setting of minimally invasive mitral valve repair. It is important to avoid over-correction by using a gentle tying of the neochordae to the chordal guiding system.