Statistical analysis of normal mitral annular geometry

The basis of mitral annuloplasty ring design has progressed from qualitative surgical intuition to experimental and theoretical analysis of annular geometry with quantitative imaging techniques. In this work, we present an automated 3D echocardiographic image analysis method that can be used to statistically assess variability in normal mitral annular geometry to support advancement in annuloplasty ring design.

3D patient-specific models of the mitral annulus are automatically generated from 3D echocardiographic images acquired from subjects with normal mitral valve structure and function. A mean 3D annular contour is computed, and principal component analysis is used to evaluate variability in normal annular shape.

normal annuli

Mean (red) and individual (blue) 3D image-derived annular contours shown from three perspectives. (AAoP = anterior aortic peak; AC = anterior commissure; PC = posterior commissure.)

normal annular shape modes

Annular height to intercommissural width ratio (AHCWR) as a function of rotational position on the annular contour. Each plot refers to one of three eigenmodes (A, mode 1; B, mode 2; C, mode 3) in shape variation obtained by principal component analysis. The red curve refers to the mean annular contour, the dark and light blue curves refer to +1 and +2 standard deviations from the mean, and the dark and light green curves refer to −1 and −2 standard deviations from the mean along a given eigenmode of shape variation. (AAoP = anterior aortic peak; AC = anterior commissure; MPA = midpoint of the posterior annulus; PC = posterior commissure.)

It is possible that a wider application of this analysis could provide information for a new generation of annuloplasty ring designs. All current designs are manufactured in a range of sizes with all sizes maintaining the same shape. With further study it may become apparent that to completely restore normal valve geometry, the next generation of saddle-shaped annuloplasty devices would best be created with subtle variations in shape as ring size increases.

  • [DOI] A. M. Pouch, M. Vergnat, J. R. McGarvey, G. Ferrari, B. M. Jackson, C. M. Sehgal, P. A. Yushkevich, R. C. Gorman, and J. Gorman 3rd, “Statistical assessment of normal mitral annular geometry using automated three-dimensional echocardiographic analysis.,” Ann Thorac Surg, vol. 97, iss. 1, pp. 71-77, 2014.
    [Bibtex]
    @ARTICLE{Pouch2014ATS,
    author = {Pouch, Alison M. and Vergnat, Mathieu and McGarvey, Jeremy R. and
    Ferrari, Giovanni and Jackson, Benjamin M. and Sehgal, Chandra M.
    and Yushkevich, Paul A. and Gorman, Robert C. and Gorman, 3rd, Joseph
    H},
    title = {{S}tatistical assessment of normal mitral annular geometry using
    automated three-dimensional echocardiographic analysis.},
    journal = {{A}nn {T}horac {S}urg},
    year = {2014},
    volume = {97},
    pages = {71--77},
    number = {1},
    month = {Jan},
    abstract = {The basis of mitral annuloplasty ring design has progressed from qualitative
    surgical intuition to experimental and theoretical analysis of annular
    geometry with quantitative imaging techniques. In this work, we present
    an automated three-dimensional (3D) echocardiographic image analysis
    method that can be used to statistically assess variability in normal
    mitral annular geometry to support advancement in annuloplasty ring
    design.Three-dimensional patient-specific models of the mitral annulus
    were automatically generated from 3D echocardiographic images acquired
    from subjects with normal mitral valve structure and function. Geometric annular
    measurements including annular circumference, annular height, septolateral
    diameter, intercommissural width, and the annular height to intercommissural
    width ratio were automatically calculated. A mean 3D annular contour
    was computed, and principal component analysis was used to evaluate
    variability in normal annular shape.The following mean ± standard
    deviations were obtained from 3D echocardiographic image analysis:
    annular circumference, 107.0 ± 14.6 mm; annular height, 7.6 ± 2.8
    mm; septolateral diameter, 28.5 ± 3.7 mm; intercommissural width,
    33.0 ± 5.3 mm; and annular height to intercommissural width ratio,
    22.7\% ± 6.9\%. Principal component analysis indicated that shape
    variability was primarily related to overall annular size, with more
    subtle variation in the skewness and height of the anterior annular
    peak, independent of annular diameter.Patient-specific 3D echocardiographic-based
    modeling of the human mitral valve enables statistical analysis of
    physiologically normal mitral annular geometry. The tool can potentially
    lead to the development of a new generation of annuloplasty rings
    that restore the diseased mitral valve annulus back to a truly normal
    geometry.},
    doi = {10.1016/j.athoracsur.2013.07.096},
    institution = {{G}orman {C}ardiovascular {R}esearch {G}roup, {U}niversity of {P}ennsylvania,
    {P}hiladelphia, {P}ennsylvania; {D}epartment of {S}urgery, {U}niversity
    of {P}ennsylvania, {P}hiladelphia, {P}ennsylvania. {E}lectronic address:
    gormanj@uphs.upenn.edu.},
    language = {eng},
    medline-pst = {ppublish},
    owner = {alison},
    pii = {S0003-4975(13)01709-8},
    pmid = {24090576},
    timestamp = {2014.02.27},
    url = {http://dx.doi.org/10.1016/j.athoracsur.2013.07.096}
    }