This chapter discusses the PULL STUDY that was designed to assess the impact of posterior leaflet coaptation pressure on anterior leaflet edge geometry in the closed valve. Figure 28.1 shows the marker locations and coordinate system used in this study. Table 28.1 identifies the datasets associated with the CONTROL and PULL runs for the three technically-satisfactory experiments analyzed (Appendix P provides these datasets). Figure 28.2 illustrates the protocol schematically.
Figure 28.1. Pull study marker locations. Marker #1=LV Apex; #2-4=LV anterior wall; #5-7= LV septum; #8-10=LV posterior wall; #11-13=LV lateral wall; #15-22=mitral annulus; #23,24,25=anterior leaflet edge; #26,27,28=posterior leaflet edge (matching pairs for #24,25,23, respectively); #29,30=anterior papillary muscle tip and base; #31,32=posterior papillary muscle tip and base. Coordinate system (green) centered on saddlehorn Marker #22, with –Z axis through apex (#1), X-Z plane containing Marker #18 (positive X towards #18), positive Y towards Marker #20.
Mitral regurgitation was trace or none during the CONTROL runs (slack suture) as assessed by Doppler Echocardiography. The posterior leaflet suture was then pulled (as illustrated in Figure 28.2) to create sustained moderate-severe regurgitation during the PULL runs.
TABLE 28.1 CONTROL PULL
pul08r23pre.1E pul08r24pull.1E pul13r01pre-2frames.1E pul13r05pull.1E pul14r01pre.1E pul14r02pull-2frames.1E
Figure 28.2. Schematic illustration of the PULL protocol In CTRL, a suture is attached to the leading edge of the central posterior leaflet scallop and exteriorized through the LV/LA interface. Control run taken with slack suture. In PULL, suture is pulled and this tension maintained to translate the central posterior leaflet scallop laterally while PULL data is recorded during several heartbeats.
The top panel in each of the Figures 28.3-28.5 shows the X, Y, and Z edge-marker coordinates and left ventricular pressure data for the three beats analyzed in each run for each heart. The bottom panel in each figure shows one of these beats with an expanded time-scale.
Table 28.2, derived from these data, shows that the end systolic position of each of the anterior and posterior leaflet edge markers was remarkably constant from beat-to-beat, varying only several tenths of a millimeter during the 3-beats of the CONTROL runs.
Table 28.3 shows the results of the PULL study, with the posterior leaflet edge markers being displaced by the suture pull by several millimeters at end-systole, while the anterior leaflet edge markers were displaced by only about 1 millimeter or less at this time. Figures 28.3-5 show that these very small displacements of the anterior leaflet edge, when posterior leaflet coaptation pressure was removed, were not just present at end systole, but characterized the entire time from end-IVC to end-IVR. Further, anterior leaflet edge position was virtually unchanged by changes in LVP, as demonstrated by the large change in LVP between the control and pull runs in Figure 28.5, and the fact that anterior leaflet edge position is also virtually invariant as pressure drops during IVR from peak systolic LVP to low end-IVR values in each heart.
Thus the position of the anterior leaflet edge, once established at end IVC, shows high beat-to-beat reproducibility and is virtually independent of changes in left ventricular pressure, the changing geometry of the LV throughout ejection and isovolumic relaxation, and the pressure of the coapting posterior leaflets in the closed valve. These data are consistent with the results discussed in Chapter 13 obtained from other hearts (H1-H6). This anterior leaflet edge position invariance strongly suggests that anterior leaflet shape is optimized to maintain the systolic geometry of the leaflet under widely varying conditions, and this shape was discussed in Chapters 8 and 9. But leaflet material properties are also involved, as the anterior leaflet supports extensive radial compression, as demonstrated in Chapter 11. In the next chapter, we will provide further information about the very complex material properties of the anterior leaflet.
Figure 28.3. Heart PUL08. Marker X-coordinate (red), Y-coordinate (green), Z-coordinate (blue), LVP/4 (black). CONTROL (solid lines). PULL (dashed lines). Top panel, 3 beats; bottom panel, enlarged time-scale single beat from the top panel.
Figure 28.4. Heart PUL14. Marker X-coordinate (red), Y-coordinate (green), Z-coordinate (blue), LVP/4 (black). CONTROL (solid lines). PULL (dashed lines). Top panel, 3 beats; bottom panel, enlarged time-scale single beat from the top panel.
Figure 28.5. Heart PUL13. Marker X-coordinate (red), Y-coordinate (green), Z-coordinate (blue), LVP/4 (black). CONTROL (solid lines). PULL (dashed lines). Top panel, 3 beats; bottom panel, enlarged time-scale single beat from the top panel.
HEART
X#23
X#24
X#25
X#28
X#26
X#27
PUL08R23
0.1
0.2
0.3
0.1
0.1
0.2
PUL13R01
0.1
0.2
0.2
0.2
0.3
0.2
PUL14R01
0.1
0.1
0.3
0.2
0.7
0.2
X MEAN
0.1
0.2
0.3
0.1
0.3
0.2
HEART
Y#23
Y#24
Y#25
Y#28
Y#26
Y#27
PUL08R23
0.1
0.2
0.4
0.2
0.2
0.4
PUL13R010.2
0.4
0.3
0.3
0.2
0.3
PUL14R010.3
0.1
0.4
0.3
0.5
0.2
Y MEAN0.3
0.3
0.3
0.3
0.3
0.2
HEARTZ#23
Z#24
Z#25
Z#28
Z#26
Z#27
PUL08R230.3
0.5
0.3
0.6
0.2
0.2
PUL13R010.2
0.2
0.1
0.2
0.1
0.3
PUL14R010.4
0.4
0.3
0.3
0.3
0.5
Z MEAN0.3
0.4
0.3
0.4
0.2
0.4
HEARTD#23
D#24
D#25
D#28
D#26
D#27
PUL08R230.3
0.5
0.6
0.7
0.4
0.5
PUL13R010.3
0.5
0.3
0.4
0.3
0.4
PUL14R010.5
0.4
0.6
0.4
0.9
0.6
3D MEAN0.4
0.5
0.5
0.5
0.5
0.5
TABLE 28.3 DIFFERENCE IN X,Y,AND Z-VALUES (ES,3-BEAT MEANS, mm) CONTROL TO PULL HEART
X#23
X#24
X#25
X#28
X#26
X#27
PUL08R23_24-0.1
-0.2
-0.2
5.1
1.4
-0.2
PUL13R01_050.9
0.8
0.9
3.6
1.1
2.4
PUL14R01_021.0
1.3
1.0
5.9
1.9
1.0
X MEAN0.6
0.6
0.5
4.8
1.5
1.1
HEART
Y#23
Y#24
Y#25
Y#28
Y#26
Y#27
PUL08R23_24