CHAPTER 05 ANTERIOR LEAFLET MOBILITY

(1)

CHAPTER 05 ANTERIOR LEAFLET MOBILITY 5-1

CHAPTER 05 ANTERIOR LEAFLET MOBILITY

In Chapter 04 we explored the displacements of the two anterior leaflet regions near the trigones associated with the APT-LFT-SH and PPT-RFT-SH planes and found that, at ED, these regions are nearly contained within these planes. In this chapter, we pull back and look at displacements throughout the cardiac cycle of the entire anterior leaflet, this time with respect to a plane formed by the saddlehorn and the two papillary tips (i.e. APT-SH-PPT).

These displacements were quantified by defining, for each frame in each heart, an APT-SH-PPT (#31-#22-#33) plane containing the X-Y basis vectors in a Euclidian reference system with positive Z defined toward the left atrium and negative Z toward the LV. For each beat, a mid-systolic frame (fs) was defined, and the Z-coordinate of each marker (Z(m,fs)) obtained for that frame (this was not a critical time-choice because the leaflet marker Z-coordinates were virtually unchanging throughout systole). During the following diastole, the frame (fd) containing the maximum excursion of the central

meridional edge marker (#38) was identified and the Z-coordinate of each marker (Z(m,fd)) obtained for that frame. The total displacement for each marker during LV filling was then computed as ΔZ(m) =Z(m,fs)- (Z(m,fd), which was positive if the displacement of that marker was towards the left atrium and negative if the displacement of that marker was towards the left ventricle during LV filling. Figure 5.1 maps these total displacements for the six hearts (H1-H6). As expected, the leaflet edge is highly mobile, with displacements of up to 15mm during opening. What is new here, however, is the demonstration that the annular half of the leaflet has severely restricted mobility, with excursions of only a few mm throughout the entire cardiac cycle. The picture that emerges is that of a quite immobile anterior leaflet hinge region, with a highly mobile edge that is responsible for most of the leaflet

opening motion. This was previously demonstrated for the central anterior leaflet meridian in Karlsson, et al.1_{, but is shown here to hold for the entire leaflet.}

Figures 5.2A-F illustrates this leaflet motion for 8 time-points from diastole to systole for each heart H1-H6, as viewed edge-on from the LFT to the RFT. Leaflet edge mobility is seen to be in sharp contrast to the almost immobile annular region of the anterior leaflet.

Interestingly, the leaflet annular region between the two strut trampolines seems just as immobile as the trampoline regions throughout the cardiac cycle. We explore some implications of this finding in the next chapter.

REFERENCES

1. Karlsson MO, Glasson JR, Bolger AF, Daughters GT, Komeda M, Foppiano LE, Miller DC, Ingels NB, Jr. Mitral valve opening in the ovine heart. Am J Physiol. 1998;274(2 Pt 2):H552-563.

(2)

Figure 5.1 Maximum anterior leaflet regional displacements (mm) from the APT-SH-PPT plane during valve opening for hearts H1-H6. See definitions in text. Medium Red = ≤1mm displacement during opening relative to this plane; Dark Red= displacements away from the LV during valve opening; Yellow-Blue=displacements toward the LV during valve opening. Red dots are marker locations as viewed along the +Z-axis toward the X-Y plane. Lines connect trigone region markers to the APT marker (#31) to the left and the PPT marker (#33) to the right.

(3)

Figure 5.2A. Left ventricular pressure (LVP) and left ventricular inflow (FLOW) at 8 time points (❶-❽) during diastole and early systole for heart (H1). The time of mitral valve closure (MVC) is identified in the bottom panel. The top 8 panels show, for each of the time points ❶-❽, the geometry of the anterior mitral leaflet, an outline of the mitral annulus, and the orientation of eight potential secondary (strut) chordae, 4 each converging on the anterior and posterior papillary tips (shown in the lower right of each panel).

(4)

Figure 5.2B. Left ventricular pressure (LVP) and left ventricular inflow (FLOW) at 8 time points (❶-❽) during diastole and early systole for heart (H2). The time of mitral valve closure (MVC) is identified in the bottom panel. The top 8 panels show, for each of the time points ❶-❽, the geometry of the anterior mitral leaflet, an outline of the mitral annulus, and the orientation of eight potential secondary (strut) chordae, 4 each converging on the anterior and posterior papillary tips (shown in the lower right of each panel).

(5)

Figure 5.2C Left ventricular pressure (LVP) and left ventricular inflow (FLOW) at 8 time points (❶-❽) during diastole and early systole for heart (H3). The time of mitral valve closure (MVC) is identified in the bottom panel. The top 8 panels show, for each of the time points ❶-❽, the geometry of the anterior mitral leaflet, an outline of the mitral annulus, and the orientation of eight potential secondary (strut) chordae, 4 each converging on the anterior and posterior papillary tips (shown in the lower right of each panel).

(6)

Figure 5.2D Left ventricular pressure (LVP) and left ventricular inflow (FLOW) at 8 time points (❶-❽) during diastole and early systole for heart (H4). The time of mitral valve closure (MVC) is identified in the bottom panel. The top 8 panels show, for each of the time points ❶-❽, the geometry of the anterior mitral leaflet, an outline of the mitral annulus, and the orientation of eight potential secondary (strut) chordae, 4 each converging on the anterior and posterior papillary tips (shown in the lower right of each panel).

(7)

Figure 5.2E Left ventricular pressure (LVP) and left ventricular inflow (FLOW) at 8 time points (❶-❽) during diastole and early systole for heart (H5). The time of mitral valve closure (MVC) is identified in the bottom panel. The top 8 panels show, for each of the time points ❶-❽, the geometry of the anterior mitral leaflet, an outline of the mitral annulus, and the orientation of eight potential secondary (strut) chordae, 4 each converging on the anterior and posterior papillary tips (shown in the lower right of each panel).

(8)

Figure 5.2F Left ventricular pressure (LVP) and left ventricular inflow (FLOW) at 8 time points (❶-❽) during diastole and early systole for heart (H6). The time of mitral valve closure (MVC) is identified in the bottom panel. The top 8 panels show, for each of the time points ❶-❽, the geometry of the anterior mitral leaflet, an outline of the mitral annulus, and the orientation of eight potential secondary (strut) chordae, 4 each converging on the anterior and posterior papillary tips (shown in the lower right of each panel).