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A Novel Surgical and Trans-catheter Mitral Repair Device: Tested Using an in vivo Sheep Model of Severe Mitral Regurgitation
Arthur C. Hill, M.D.1, Michael Lesh, M.D.2, Alexander Khairkhahan2.
1University of California, San Francisco, San Francisco, CA, USA, 2Middle Peak Medical, Palo Alto, CA, USA.

We are developing a novel percutaneous transcatheter implant
for treating severe mitral regurgitation (MR). The device, constructed of
standard surgical materials, provides a polymeric posterior leaflet surface, restoring normal coaptation with the anterior leaflet. We describe here proof-of-concept by evaluating MR elimination using open surgical implantation in sheep. A second phase of the project will consist of in vivo testing of the percutaneous trans-septal system.

In 9 sheep, we created a model of severe (4+) flail MR by severing one or more chords to P2. After minimally invasive left thoracotomy and cardiopulmonary bypass, the device was surgically implanted, and the animal weaned from CPB. Residual MR was evaluated by ventriculography and/or epicardial and transthoracic echocardiography. Sacrifice was acute in 4 and chronic in 5 (1-7 months post-operatively).

Flail P2 with 4+ MR was successfully created in all sheep; this preparation was documented to produce immediate fatality without repair. Device implantation resulted in MR ≤ 1+ in 4/4 acute and 4/5 chronic sheep. Clinical status at follow up, residual MR, thrombosis, and histopathology for the chronic group is shown in Table I.

In an ovine model of flail P2, we demonstrated that a novel mitral
implant can eliminate 4+ MR by providing a new surface onto which the anterior leaflet may coapt. No thromboemboli or other complications occurred. The device has undergone minor iterative modification and has characteristics that will allow its use in posterior leaflet degenerative disease, functional MR, and rheumatic MR. Development
of a 16Fr percutaneous transcatheter delivery system is ongoing. In addition, surgical implantation in patients with severe MR is an option using minimally invasive and robotic approaches.

Results of Chronic Animals
Time at SacraficeCHFMR GradePathologyComplications
1 moModerate3+Large Heart; implant undersized; no clot
6 mo0traceAttachment well healed; Surface endothelializationNone
6 mo0traceAttachment well healed; Surface endothelialization
7 mo0mildAttachment well healed; Surface endothelialization
Alive at 1 mo0PendingPendingNone

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