Session MD.1

3D Analysis of Transmural Myocardial Strain from Sonomicrometric Crystals in the Open Chest Dog

A Ragnoni, G Saracino*, C Corsi, N Greenberg,
C Lamberti, JD Thomas

The Cleveland Clinic
Cleveland, OH, USA

The interest of Left Ventricular (LV) mechanics has recently focused on detailed 3D analysis of LV deformations. Our goal is to enable transmural strain analysis within LV wall to investigate strain variability within the normal ventricle and during the early stages of ischemia and necrosis which always affect the inner layer of the ventricle first. We have developed a method of implanting up to 16 sonomicrometric crystals into LV wall in order to measure regional deformations in open chest dog model. In this study 3 open chest dogs were implanted with crystals in a two-tetrahedron configuration with three crystals on the epicardial surface, three on the endocardial surface and one in the LV midwall. Additional crystals were implanted in the LV apex, at the origin of LAD coronary artery, and to the posterior-lateral wall in order to impose a fiducial plane. Our algorithm numerically reconstructed the relative position in 3D space of crystals that were implanted throughout the cardiac cycle. The initial set of x, y, z coordinates of each crystal is iteratively adjusted to minimize an error function that weights the matrix of transmitter-receiver distances with a computed quality factor of each signal acquired. The reconstructed 3D configuration of the crystals and its deformation during the cardiac cycles is then used to provide information regarding the local ventricular mechanics including radial, longitudinal and circumferential strain. EKG signal was used to define cardiac cycles. Pressure-volume signals were also acquired using a catheter introduced to LV from the femoral artery. The algorithm was successfully reconstructed the 3D geometry of the implanted crystals, although in some instances we had to fine tune the matrix of the weight factors due to signal noise. Results obtained clearly illustrate a difference in strain across the myocardium with range of endocardial strain being greater than epicardial. The area between the endocardial crystals consistently decreased in the time during cardiac contraction. However, epicardial areas first slightly increased and then decreased with velocities that were different in each animal. This study shows that the method can disclose important information regarding transmural variability in animal model and further investigation with different pacing and conditions could enhance understating of LV Mechanics.

(Abstract Control Number: 230)