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Original Articles: Adult Cardiac

Saddle Shape of the Mitral Annulus Reduces Systolic Strains on the P2 Segment of the Posterior Mitral Leaflet

^a Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia
^b Department of Cardiothoracic Surgery, University of Pennsylvania, Glenolden Laboratories, Glenolden, Pennsylvania
^c Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania

Accepted for publication June 16, 2009.

^_* Address correspondence to Dr Padala, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 315 Ferst Dr NW, Atlanta, GA 30332 (Email: mpadala{at}gatech.edu).

Background: The three-dimensional saddle shape of the mitral annulus is well characterized in animals and humans, but the impact of annular nonplanarity on valve function or mechanics is poorly understood. In this study, we investigated the impact of the saddle shaped mitral annulus on the mechanics of the P2 segment of the posterior mitral leaflet.

Methods: Eight porcine mitral valves (n = 8) were studied in an in-vitro left heart simulator with an adjustable annulus that could be changed from flat to different degrees of saddle. Miniature markers were placed on the atrial face of the posterior leaflet, and leaflet strains at 0%, 10%, and 20% saddle were measured using dual-camera stereophotogrammetry. Averaged areal strain and the principal strain components are reported.

Results: Peak areal strain magnitude decreased significantly from flat to 20% saddle annulus, with a 78% reduction in the measured strain over the entire P2 region. In the radial direction (annulus free edge), a 44.4% reduction in strain was measured, whereas in the circumferential direction (commissure-commissure), a 34% reduction was measured from flat to 20% saddle.

Conclusions: Nonplanar shape of the mitral annulus significantly reduced the mechanical strains on the posterior leaflet during systolic valve closure. Reduction in strain in both the radial and circumferential directions may reduce loading on the suture lines and potentially improve repair durability, and also inhibit progression of valve degeneration in patients with myxomatous valve disease.

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