Three-dimensional regional dynamics of the normal mitral anulus during left ventricular ejection

Abstract

The mitral anulus is a dynamic structure that undergoes alterations in size and shape throughout the cardiac cycle, contracting during systole. Numerous reports have shown this systolic orifice reduction to be due chiefly to posterior annular contraction, whereas the anterior perimeter was unchanged. Segmental motion of the mitral anulus from true in vivo three-dimensional data, however, has not been described. We used radiopaque markers and simultaneous biplane videofluoroscopy to measure the lengths of mitral anular segments in seven closed-chest, sedated dogs. Eight markers were placed equidistant from each other around the mitral anulus, As viewed from the left atrium, segment 1 began at the posteromedial commissure, and the remaining segments were numbered sequentially clockwise around the anulus (that is, the posterior mitral anulus encompassed segments 1 to 4 and the anterior anulus encompassed segments 5 to 8). Marker image coordinates obtained from two orthogonal views 7 to 12 days after implantation were merged to construct three-dimensional marker coordinates at end-diastole and end-systole. From end-diastole to end-systole, mean annular area decreased by 11% +/- 8% (5.5 +/- 0.9 cm2 to 4.9 +/- 0.8 cm2, p = 0.005) and perimeter by 5% +/- 4% (8.8 +/- 0.7 cm to 8.3 +/- 0.7 cm, p < 0.01). Mitral annular segmental percent systolic shortening (negative values indicate lengthening) were as follows (mean +/- standard deviation): segment 1, 7% +/- 9%; segment 2, 8% +/- 10%; segment 3, 16% +/- 6%; segment 4, 10% +/- 7%; segment 5, -4% +/- 5%, segment 6, -7% +/-7%; segment 7, 3% +/- 2%; and segment 8, 6% +/- 5%. With the exception of segment 1, all posterior (2 to 4) and two anterior (7 and 8) mitral annular segments contracted significantly (p < or = vs zero, paired t test). Two anterior annular segments (5 and 6, regions overlapping aortic-mitral continuity), however, unexpectedly lengthened during left ventricular systole. We conclude that the anterior mitral anulus may be a much more dynamic component of the mitral apparatus that previously thought. Such heterogeneous dynamic annular motion should be taken into account when various mitral valve reparative techniques are being designed.

Mitral valve repair with a malleable bovine pericardium ring

“…Differing annuloplasty adopts as a basis for measurement in the choice of the different size rings, the intertrigonal or intercommissural distance, associated or not with the measurement of the anterior leaflet's area 10,13,[27][28][29][30] . Yet, the mitral annulus does not maintain size and form constant during systole and the annulus segment over the area of aortic-mitral continuity is significantly lengthened during ventricular systole 47 . Thus, such measurements do not seem to favor an adequate estimate for the selection of annular prosthesis' size, justifying the development of devices to measure anterior cusp perimeters 26 .…”

Mitral Annular Dilatation and Papillary Muscle Dislocation Without Mitral Regurgitation in Sheep

“…16 The details of this data reduction procedure have been published previously. 17,18 The descending thoracic aortic pressure, LV pressure, and ECG voltage were simultaneously digitized and recorded in real-time on the video images during data acquisition.…”

Characterization of Mitral Valve Annular Dynamics in the Beating Heart

“…22,42,45 Numerous studies proved the mitral annulus to undergo complex three-dimensional (3D) deformation throughout the cardiac cycle with characteristic changes in its geometric parameters including saddle height (SH), septal-lateral diameter, commissure-commissure diameter, and mitral annular area (MAA). 18,48,51 Shape, size, and dynamics of the mitral annulus are closely related to mitral valve function; deviations from the normal have been associated with mitral valve insufficiency. Typical examples of pathologies that affect mitral annular shape and kinematics are ischemic and dilated cardiomyopathy.…”

“…Linear interpolation has been widely used among clinical researchers to characterize the mitral annulus in humans and in animal models. 18,20,21,48 More sophisticated approaches use one-dimensional (1D) interpolating Hermitian finite elements 13 or Fourier series to approximate the mitral annulus from echo data. 36 An alternative method to reconstruct space curves that provides a variety of practical advantages is spline fitting.…”