Including transmural crossover of myofibers in a finite-element model of LV mechanics was essential to accurately simulate the realistic time course and amplitude (~0.1) of midwall shear strain.
Transmural crossover of myofibers is essential for realistic mathematical modeling of left ventricular wall mechanics and shear strain.
Mathematical models of cardiac mechanics can potentially be used to relate abnormal cardiac deformation, as measured noninvasively by ultrasound strain rate imaging or magnetic resonance tagging (MRT), to the underlying pathology. However, with current models, the correct prediction of wall shear strain has proven to be difficult, even for the normal healthy heart. Discrepancies between simulated and measured strains have been attributed to 1) inadequate modeling of passive tissue behavior, 2) neglecting active stress development perpendicular to the myofiber direction, or 3) neglecting crossover of myofibers in between subendocardial and subepicardial layers. In this study, we used a finite-element model of left ventricular (LV) mechanics to investigate the sensitivity of midwall circumferential-radial shear strain (E(cr)) to settings of parameters determining passive shear stiffness, cross-fiber active stress development, and transmural crossover of myofibers. Simulated time courses of midwall LV E(cr) were compared with time courses obtained in three healthy volunteers using MRT. E(cr) as measured in the volunteers during the cardiac cycle was characterized by an amplitude of approximately 0.1. In the simulations, a realistic amplitude of the E(cr) signal could be obtained by tuning either of the three model components mentioned above. However, a realistic time course of E(cr), with virtually no change of E(cr) during isovolumic contraction and a correct base-to-apex gradient of E(cr) during ejection, could only be obtained by including transmural crossover of myofibers. Thus, accounting for this crossover seems to be essential for a realistic model of LV wall mechanics.
Bovendeerd et al. (Sat,) conducted a other in Healthy heart (n=3). Finite-element model of LV mechanics including transmural crossover of myofibers vs. Magnetic resonance tagging (MRT) in healthy volunteers was evaluated on Midwall circumferential-radial shear strain (E(cr)) time course and amplitude. Including transmural crossover of myofibers in a finite-element model of LV mechanics was essential to accurately simulate the realistic time course and amplitude (~0.1) of midwall shear strain.