The loading and function of the mitral valve under normal, pathological and repair conditions: an in vitro study

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Jimenez-Mejia, Jorge Hernan
Yoganathan, Ajit P.
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Currently, mitral valve repair techniques have shown substandard mid-term and long term results. In order to improve the efficacy of these repair techniques, detailed knowledge of normal mitral valve function and the alterations to the valvular and subvalvular apparatus which occur under pathological conditions is required. Furthermore, current techniques may be optimized through a better understanding of the function and mechanics of the mitral valve after a particular repair. The experiments which comprise this study were designed using an in vitro approach since this technique has the clear advantage of isolating and independently controlling specific parameters that are of importance to valvular mechanics and function. The experiments were conducted in the Georgia Tech Left Heart Simulator using native porcine and human mitral valves. The first set of experiments measured the chordal force distribution and anterior leaflet strain of the mitral valve in its normal geometrical configuration. Subsequent experiments measure mitral regurgitation volume and chordal force distribution in conditions associated with ventricular dilation. The last set of experiments simulated two commonly used mitral repair techniques. For the Alfieri stitch experiments, the effects of mitral flow rate, transmitral pressure, and mitral annular area on valve stenosis, mitral regurgitation and Alfieri stitch force were evaluated. For annuloplasty, the effect of annular saddle curvature on anterior leaflet strain was quantified. In Conclusion, the normal geometry of the native mitral valve optimized its function and mechanics. Under pathological conditions associated with ventricular dilation, significant alterations to mitral valve function and mechanics were present. Although the studied repair techniques may have significantly restored valve function, severe alterations to the mechanics of the valve still persisted.
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