Papillary Muscle Misalignment Causes Multiple Mitral Regurgitant Jets: An Ambiguous Mechanism for Functional Mitral Regurgitation Sten L. Nielsen MD, Hans Nygaard DMSc, Arnold A. Fontaine PhD, J. Michael Hasenkam MD, Shengqui He MD, Ajit P. Yoganathan PhD The impact of papillary muscle (PM) alignment on mitral valve competence were investigated in vitro to test the hypothesis that such misalignment is sufficient to cause functional mitral regurgitation (MR). Papillary muscle misalignment moved the mitral leaflet edges in apical and posterior direction, which created a commissural regurgitant orifice at the same side of PM displacement. Contralaterally, anterior leaflet prolapse and restricted posterior leaflet mobility were responsible for an additional commissural regurgitant jet. Symmetrical PM displacement restricted mitral leaflet mobility on both commissural sides and created a large mitral regurgitant jet, which originated centrally and extended towards both commissures. PM misalignment caused multiple mitral regurgitant jet locations which can obscure the exact structural basis for functional MR. These findings may improve understanding of the relation between myocardial lesion and mitral regurgitant jet location, and thereby facilitate rational strategies for valvular interventions.

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