BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Efficient Quantification of Left Ventricular Function During the F ull Cardiac Cycle Using a Characteristic Deformation Model - Brian Hong (N one / Other) DTSTART:20190606T110000Z DTEND:20190606T113000Z UID:TALK125626@talks.cam.ac.uk CONTACT:INI IT DESCRIPTION: Heart failure is a significant source of morb idity and the prevalence of heart failure continues to rise. Quantificat ion of cardiac function beyond standard clinical indices is essential to improving heart failure diagnosis specificity. Patient-specific computa tional models of the heart offer detailed descriptions of cardiac functi on suitable for this purpose. Such models are typically constructed usin g 0D &ldquo\;varying elastance&rdquo\; or 3D Finite element method (FEM) approaches. While both methods have been successfully applied to many p atient-specific applications\, each has limitations. Varying elastance m odels are limited by their simplified representation of the myocardium w hile FEM models have a high computational cost that is restrictive in ap plications that require the simulation of many cardiac cycles. As an alt ernative to these approaches\, we describe a computationally efficient m ethod for simulating the dynamics of the left ventricle (LV) in three di mensions using characteristic deformation modes (CDM). In the CDM-LV mod el\, LV motion is represented as a combination of a limited number of de formation modes\, chosen to represent observed cardiac motions. A variat ional approach is used to incorporate a mechanical model of the myocardi um. Passive stress is governed by a transversely isotropic elastic model . Active stress acts in the fiber direction and incorporates length-tens ion and force-velocity properties of cardiac muscle.

We a pply this model to quantify LV function in two cases. \; First\, we qu antify the passive stiffness of a mouse heart. The stiffness parameters of the mouse LV calculated with the CDM model are similar to those ident ified using a FEM approach. Second\, we quantify LV function during the full cardiac cycle from 3D echocardiogram data. We estimate parameters f or the myocardial passive stiffness and active contractile function usin g a bounded quasi-newton numerical optimization algorithm. We demonstrat e that this method is capable of recapitulating the observed aggregated motion of the LV and provides reasonable estimates for the mechanical pa rameters. The problem of estimating LV functional parameters has numerou s sources of uncertainty. Errors arise from the limitations of the imagi ng method\, insufficiency of the data to fully characterize the mechanic al system\, and from simplifications present in the mathematical model. We present a preliminary analysis of the uncertainty resulting from thes e three sources. Overall\, this approach provides reasonable estimates for the mechanical parameters that determine LV function on a clinically re levant time-scale. LOCATION:Seminar Room 1\, Newton Institute END:VEVENT END:VCALENDAR