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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Efficient Quantification of Left Ventricular Funct
ion During the Full Cardiac Cycle Using a Characte
ristic Deformation Model - Brian Hong (None / Othe
r)
DTSTART;TZID=Europe/London:20190606T120000
DTEND;TZID=Europe/London:20190606T123000
UID:TALK125626AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/125626
DESCRIPTION: Heart failure is a significant so
urce of morbidity and the prevalence of heart fa
ilure continues to rise. Quantification of cardiac
function beyond standard clinical indices is es
sential to improving heart failure diagnosis spe
cificity. Patient-specific computational models of
the heart offer detailed descriptions of cardia
c function suitable for this purpose. Such model
s are typically constructed using 0D &ldquo\;varyi
ng elastance&rdquo\; or 3D Finite element method
(FEM) approaches. While both methods have been su
ccessfully applied to many patient-specific appl
ications\, each has limitations. Varying elastan
ce models are limited by their simplified represen
tation of the myocardium while FEM models have a
high computational cost that is restrictive in
applications that require the simulation of many c
ardiac cycles. As an alternative to these approa
ches\, we describe a computationally efficient m
ethod for simulating the dynamics of the left vent
ricle (LV) in three dimensions using characteris
tic deformation modes (CDM). In the CDM-LV model
\, LV motion is represented as a combination of a
limited number of deformation modes\, chosen to
represent observed cardiac motions. A variationa
l approach is used to incorporate a mechanical mod
el of the myocardium. Passive stress is governed
by a transversely isotropic elastic model. Acti
ve stress acts in the fiber direction and incorpor
ates length-tension and force-velocity propertie
s of cardiac muscle.

We apply thi
s model to quantify LV function in two cases.
\; First\, we quantify the passive stiffness of
a mouse heart. The stiffness parameters of the mou
se LV calculated with the CDM model are similar
to those identified using a FEM approach. Second\,
we quantify LV function during the full cardiac
cycle from 3D echocardiogram data. We estimate
parameters for the myocardial passive stiffness an
d active contractile function using a bounded qu
asi-newton numerical optimization algorithm. We
demonstrate that this method is capable of recapit
ulating the observed aggregated motion of the LV
and provides reasonable estimates for the mecha
nical parameters. The problem of estimating LV fun
ctional parameters has numerous sources of uncer
tainty. Errors arise from the limitations of the
imaging method\, insufficiency of the data to ful
ly characterize the mechanical system\, and from
simplifications present in the mathematical mod
el. We present a preliminary analysis of the uncer
tainty resulting from these three sources. Overa
ll\, this approach provides reasonable estimates f
or the mechanical parameters that determine LV f
unction on a clinically relevant time-scale.
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:info@newton.ac.uk
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