Development of an ex vivo pulsatile heart model of functional mitral regurgitation to facilitate posterior papillary muscle geometric studies and subvalvular surgical strategy
Kradangnga, Krishaporn, author
Monnet, Eric, advisor
Orton, Christopher, committee member
Boscan, Pedro, committee member
Dasi, Lakshmi P., committee member
Surgical method of choice for functional ischemic mitral regurgitation (FIMR) is debatable, since recurrence of FIMR post-annuloplasty has been reported in significant number of cases. Developing an ex vivo pulsatile functional mitral regurgitation (FMR) heart model by left ventricular (LV) dilatation can be a favorable option for usage in the primary stages of developing new surgical techniques that adjunctively targets the posterior papillary muscle (PPM) geometry. Posterior papillary muscle of ex vivo ovine hearts was displaced by 3 different sizes of patches to induce LV dilatation and FMR. Mitral regurgitation (MR) flow, LV and annular geometry were measured from the dynamic pulsatile flow system before and after patch placement. Applying the large patch produced the highest proportion of FMR heart models (87.5%, P=0.031). In conclusion, the large patch ex vivo pulsatile heart model demonstrated outward displacement of the PPM and significantly produced MR flow. This ex vivo pulsatile heart model can be used to facilitate surgical techniques that targets the PPM displacement in FMR patients. The following phase of our research was aimed to utilize this ex vivo pulsatile heart model for PPM geometric studies in FMR with PPM displacement despite normal mitral annulus. This scenario mimics post-annuloplasty cases when the annular dilatation was corrected by ring annuloplasty but the underlying LV remodeling was not treated. Sonomicrometry was used to evaluate the three-dimensional tethered distances and tethered angles of the PPM due to regional LV dilatation. The findings of this study implied that although annular dilatation was normalized, the increased PPM displacement outside and away from the mitral ring could deteriorate mitral leaflet tethering. The decreased tethering angle of the PPM from the annular fibrosa, reflecting the overall anterior mitral leaflet (AML) tethering and AML bending, could be used for MR prediction. Lastly, the ex vivo pulsatile heart model with PPM lateral displacement and septo-lateral annular dilatation was used to facilitate additional subvalvular surgical strategy. Reduction annuloplasty was used as the standard FIMR treatment but showed suboptimal results with recurrent MR. Post-annuloplasty progression of LV remodeling and papillary muscles displacement could increase leaflet tethering. Annuloplasty alone did not correct submitral problems, therefore, adjunct procedures should be used to address the LV remodeling, prevent recurrent FIMR and insure durability of the balanced mitral complex mechanisms after surgery. In addition to septo-lateral mitral annular reduction, the PPM repositioning was done by using the epicardial apparatus to baso-medially relocate the PPM base toward the mitral fibrosa. The concept of this technique was to reduce the tethering distance of the PPM from the mitral annulus and the interpapillary muscle distance. In conclusion, this study demonstrates the feasibility of an epicardial correction to study geometric changes after mitral annular reduction alone compared to PPM repositioning adjunct with mitral annulus reduction in a pulsatile ex vivo heart model of FMR. This study was aimed to fulfill the gap of the complex FIMR mechanisms and provides preliminary data of the mitral geometry from PPM repositioning outside the LV chamber.
Includes bibliographical references.
Includes bibliographical references.
functional ischemic mitral regurgitation
papillary muscle displacement