In-Vivo Dynamic Deformation of the Mitral Valve Anterior Leaflet Michael S. Sacks, PhD, Yoshiharu Enomoto, MD, Jeffrey R. Graybill, BS, W. David Merryman, MS, Ahmad Zeeshan, MD, Ajit P. Yoganathan, PhD, Robert J. Levy, MD, Robert C. Gorman, MD, Joseph H. Gorman, MD  The Annals of Thoracic Surgery  Volume 82, Issue 4, Pages 1369-1377 (October 2006) DOI: 10.1016/j.athoracsur.2006.03.117 Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 1 (a) A schematic of the mitral valve anterior leaflet showing the nine sonomicrometry transducer array. (b) An interoperative view of the anterior mitral leaflet as seen through a left atriotomy. The relationships of the leaflet, transducers, wires, and atrium are shown. The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 2 (A) A schematic of the nine sonocrystals placement on the mitral valve anterial leaflet surface, showing crystal positions in relation to valvular geometry, with c-circumferential and r-radial directions. (B) Two three-dimensional reconstructed views of the nine sonocrystals in the unloaded reference state (t = 0 ms) and the fully coapted state (t = 500 ms). Also shown below is a schematic showing the anatomic location of the nine crystals on the mitral valve anterior leaflet. Color fringes represent the relative change in area D = current area/original area. In the fully coapted state, homogeneity of the change in area was noticeable. However, most of the area delimited by the crystals was relatively homogenous and was represented by the value at the center crystal (no. 6). (Ao = aortic location; AC = anterior commissure; Co = coronary sinus location; PC = posterior commissure.) The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 3 Echocardiographic image of a representative ovine mitral valve during systole (left) and diastole (right). The shape and motion of all instrumented valves was unchanged by placement of the sonomicrometry transducers as assessed by echocardiography. “Wi” marks the transducer wires as they pass through the left atrium. The triangles mark individual transducers on the anterior leaflet. (aMV = anterior mitral valve leaflet; AO = aorta; LA = left atrium; LV = left ventricle; pMV = posterior mitral valve leaflet.) The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 4 Representative time-stretch and time-areal strain traces, along with the corresponding strain rate data. We observed large anisotropic (ie, directionally dependent) strains. More importantly, the corresponding strain rates were quite high, on the order of 100%/s to 400%/s, underscoring the highly dynamic nature of the mitral valve. The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 5 Mean principal strains (a, b) and areal strain (c) for all three pressures levels for the current study, where in (a) the asterisk (*) indicates a statistically significant difference (p < 0.05) from the corresponding radial stretch at 90 mm Hg. Other than the differences between circumferential (circ) and mean radial peak strains, there were no significant differences with increasing LV pressure. In (d) are also shown for comparison the corresponding in-vitro data reproduced from [16], with substantially larger mean peak strains. **Statistically different from circumferential mean (p < 0.05). The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 6 Mean principal peak strain rates for all three pressure level groups. While there were statistically significant differences between the radial group (black bars) and circumferential group (gray bars; p < 0.05), there were no differences due to increasing left ventricular pressure. The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 7 A representative left ventricular (LV) pressure–areal strain curve, which is analogous to a stress–strain curve for the leaflet and demonstrates the classic nonlinear soft tissue response. Note, too, the near-linear response for LV pressures above 20 mm Hg. The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 8 (a) Representative linear regions from the left ventricular (LV) pressure–areal strain curves (others not shown for clarity), demonstrating the consistency of response. (b) Unlike the peak deformations results (Fig 4), the mean effective leaflet stiffness demonstrated statistically significant increases with peak LV pressure. The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions

Fig 9 Principal stretch traces for both the current in-vivo data (open triangles [a, c, d]; open circles [b]) and the in-vitro data (solid circles) from our previous study [25]. Here, the peak stretches were normalized to unity, and the time normalized to one complete valve open/closed cycle. Of particular interest is the similarity in qualitative responses between the present ovine in-vivo and our previous porcine in-vitro responses. The Annals of Thoracic Surgery 2006 82, 1369-1377DOI: (10.1016/j.athoracsur.2006.03.117) Copyright © 2006 The Society of Thoracic Surgeons Terms and Conditions