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Reducing mitral valve regurgitation through constriction of the annulus Holloway, Daniel Douglas


Introduction Mitral valve regurgitation (MR) is a result of hemodynamic incompetence of the mitral valve. An in-vitro model of MR was developed to investigate type II and type III-b mitral dysfunction. The role of annular constriction in the reduction of MR was investigated. Methods A porcine heart was mounted in the apparatus. Chords were shortened, lengthened, and cut to create a restricted leaflet, a prolapsed leaflet, and a flail leaflet, respectively. A novel annular constriction device was implanted onto the outside surface of the heart. The magnitude of MR was measured for each created lesion at annular constrictions of 10%, 30%, and 50%. The regurgitation flow rate and the change in regurgitation relative to the disease regurgitation rate were calculated. Results Creation of mitral valve lesions produced MR significantly greater than measured baseline values (p<0.0001). Annular constriction alone significantly reduced MR for a flail leaflet (p=0.0054), prolapsed leaflet (p=0.0018), and restricted leaflet (p=0.0011). The effect of lesion type does not have a significant difference on the regurgitation reduction for 10%, 30%, or 50% annular constriction. The initial disease severity appears to affect the regurgitation flow rate at 10% and 30% but not 50% annular constriction. Discussion Annular constriction, without any other surgical alteration to the valve, was found to effectively reduce MR for type III-b and type II mitral dysfunction. MR is reduced through improved leaflet coaptation as well as through formation of a monoleaflet valve where the posterior leaflet is functionally nullified and therefore lesions associated with the posterior leaflet become irrelevant. The mechanisms of MR reduction apply similarly to restricted, prolapsed, and flail leaflets. For this reason the three lesions react similarly to annular constriction. The regurgitation flow rate is dependent on the initial disease severity if the annulus is constricted 10% or 30%. If the annulus is constricted 50%, the regurgitation flow rate is reduced to the approximate baseline value regardless of the initial disease severity. Conclusion Annular constriction alone without any other surgical repair to the valve produced significant reductions in MR for type III-b restricted leaflet and type II prolapsed and flail leaflets.

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