Evidence of adaptive mitral leaflet growth

Manuel K. Rausch, Frederick A. Tibayan, D. Craig Miller, Ellen Kuhl

    Research output: Contribution to journalArticle

    36 Scopus citations

    Abstract

    Ischemic mitral regurgitation is mitral insufficiency caused by myocardial infarction. Recent studies suggest that mitral leaflets have the potential to grow and reduce the degree of regurgitation. Leaflet growth has been associated with papillary muscle displacement, but role of annular dilation in leaflet growth is unclear. We tested the hypothesis that chronic leaflet stretch, induced by papillary muscle tethering and annular dilation, triggers chronic leaflet growth. To decipher the mechanisms that drive the growth process, we further quantified regional and directional variations of growth. Five adult sheep underwent coronary snare and marker placement on the left ventricle, papillary muscles, mitral annulus, and mitral leaflet. After eight days, we tightened the snares to create inferior myocardial infarction. We recorded marker coordinates at baseline, acutely (immediately post-infarction), and chronically (five weeks post-infarction). From these coordinates, we calculated acute and chronic changes in ventricular, papillary muscle, and annular geometry along with acute and chronic leaflet strains. Chronic left ventricular dilation of 17.15% (p< 0.001) induced chronic posterior papillary muscle displacement of 13.49. mm (p=0.07). Chronic mitral annular area, commissural and septal-lateral distances increased by 32.50% (p=0.010), 14.11% (p=0.007), and 10.84% (p=0.010). Chronic area, circumferential, and radial growth were 15.57%, 5.91%, and 3.58%, with non-significant regional variations (p=0.868). Our study demonstrates that mechanical stretch, induced by annular dilation and papillary muscle tethering, triggers mitral leaflet growth. Understanding the mechanisms of leaflet adaptation may open new avenues to pharmacologically or surgically manipulate mechanotransduction pathways to augment mitral leaflet area and reduce the degree of regurgitation.

    Original languageEnglish (US)
    Pages (from-to)208-217
    Number of pages10
    JournalJournal of the Mechanical Behavior of Biomedical Materials
    Volume15
    DOIs
    StatePublished - 2012

    Keywords

    • Cardiac mechanics
    • Growth
    • Mitral leaflet
    • Mitral valve
    • Regurgitation
    • Remodeling

    ASJC Scopus subject areas

    • Biomaterials
    • Biomedical Engineering
    • Mechanics of Materials

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