An Ex Vivo Model of Left Ventricular Dilation and Functional Mitral Regurgitation to Facilitate the Development of Surgical Techniques

Abstract

<p><b>Objective:</b> Functional mitral regurgitation (FMR) is a common sequelae of myocardial ischemic disease. It results from annular dilation and outward rotation of the posterior papillary muscle. Different surgical techniques are under investigation for the treatment of FMR. However, an ex vivo model of FMR would be valuable to develop and compare the effect of techniques on the geometry of the left ventricle and the correction of FMR.</p><p><b>Methods:</b> FMR was induced in explanted ovine hearts (n = 12) by manual dilation of the mitral annulus or by posterior papillary muscle repositioning with a patch. Left ventricular dimensions were measured. Mitral regurgitant volume (MRV) was measured in a continuous flow system.</p><p><b>Results:</b> Annular dilation significantly increased MRV from 93.0 � 110.4 to 472.2 � 211.8 mL/min (<i>P</i> = 0.031), and the patch increased it from 37.8 � 55.2 to 365 � 189.6 mL/min (<i>P</i> = 0.031), with no significant differences between the 2 groups. When both techniques were applied, MRV significantly increased to 1383.5 � 567.0 mL/min (<i>P</i> = 0.0005). The left ventricular sphericity index decreased from 3.25 � 0.7 to 2.34 � 0.6 (<i>P</i> = 0.0025) after application of the patch. The posterior papillary muscle was displaced after patch placement, following an outward rotation.</p><p><b>Conclusion:</b> This ex vivo model reproduces annular dilation and outward rotation of the posterior papillary muscle, which are both present during FMR after ischemic myocardial disease. This model could be used to evaluate and compare interventions to treat FMR.</p>