CHAPTER 13 ANTERIOR LEAFLET LV POSITION 13-1
MITRAL VALVE MECHANICS by Neil B. Ingels, Jr. and Matts Karlsson CHAPTER 13 ANTERIOR LEAFLET LV POSITION
In Chapter 9 we showed that anterior mitral leaflet shape is maintained with sub-millimeter precision while the mitral valve is closed. In this chapter we assess the variability of the 3-D position of this rigid leaflet within the left ventricular chamber throughout ventricular ejection.
The Euclidian coordinate system employed for this assessment placed, for each frame (f), the
saddlehorn marker (#22) at the origin, the LV apical marker (#1) on the –z axis, and the lateral annular marker (#18) in the x-z plane. A three-beat systolic mean x-coordinate (𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑋𝑋)) for each leaflet marker (m=15, 21-24, 29, 30, 38-53) was obtained using all frames from LV outflow onset to LV outflow end for the three sequential beats. A three-beat systolic mean y-coordinate (𝑌𝑌𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑋𝑋)) and
z-coordinate (𝑍𝑍𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑋𝑋)) for each leaflet marker were obtained in similar fashion. For each frame, and each marker, the distance
𝐷𝐷(𝑓𝑓, 𝑋𝑋) = �(𝑥𝑥(𝑓𝑓, 𝑋𝑋) − 𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑋𝑋))2+ (𝑦𝑦(𝑓𝑓, 𝑋𝑋) − 𝑌𝑌𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑋𝑋))2 + (𝑧𝑧(𝑓𝑓, 𝑋𝑋) − 𝑍𝑍𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑋𝑋))2
was obtained. The mean value of all leaflet distances for each frame was then computed as
𝐷𝐷𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑓𝑓) =23 � 𝐷𝐷(𝑓𝑓, 𝑋𝑋)1
23 𝑚𝑚=1
Figure 13.1 plots 𝐷𝐷𝑋𝑋𝑋𝑋𝑋𝑋𝑋𝑋(𝑓𝑓) vs. frame for the six hearts H1-H6. The times of mitral valve closure, LV ejection onset, LV ejection maximum flow, and LV ejection end are identified in each graph. Note that the ordinate of each graph ranges from 0 to 1.2 mm.
Examination of the six graphs shows that leaflet position within the left ventricular chamber for each heart exhibits sub-millimeter reproducibility throughout ejection in each beat and from beat-to-beat for three sequential beats. Table 13.1 quantifies this reproducibility, with only one heart (H3) displaying a variation of 1.1 mm at one instant (outflow onset), while this heart at other instants, as well as the other hearts at all instants exhibited sub-millimeter 3D positional stability within the LV chamber.
Thus, we can now conclude that, not only does the anterior mitral leaflet maintain a rigid shape in the closed mitral valve, but this rigid shape is maintained in a fixed position in the left ventricular chamber throughout ejection, in spite of the fact that the papillary muscles are moving continuously inward over this interval. This is likely to be important to LV outflow, as the anterior mitral leaflet sets an important boundary for the LV outflow tract. 1
1. Dimasi A, Cattarinuzzi, E., Stevanella, M., Conti, C.A., Votta, E., Maffessanti, F., Ingels, N.B.Jr, Redaelli, A. Influence of mitral valve anterior leaflet in vivo shape on left ventricular ejection.
CHAPTER 13 ANTERIOR LEAFLET LV POSITION 13-2
MITRAL VALVE MECHANICS by Neil B. Ingels, Jr. and Matts Karlsson
Figure 13.1 H1-H6 Anterior leaflet mean LV position (DMEAN, mm). LVP=Left Ventricular Pressure (mmHg); MVC=Mitral Valve Closure; EO=LV ejection onset; EM=LV ejection maximum flow; EE=LV ejection end.
CHAPTER 13 ANTERIOR LEAFLET LV POSITION 13-3
MITRAL VALVE MECHANICS by Neil B. Ingels, Jr. and Matts Karlsson
