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Title

ANALYSIS OF TRANSPORT TOPOLOGY IN THE LEFT VENTRICLE UNDER HEALTHY AND DISEASED STATES

Creator

Hendabadi, Sahar

Date

2013, 2013-12

Description

There is evidence that under healthy conditions the vortical nature of blood in the LV optimizes pumping, yet precise characterization of...
Show moreThere is evidence that under healthy conditions the vortical nature of blood in the LV optimizes pumping, yet precise characterization of transport in the LV has been lacking. Because the ventricle is not completely emptied during ejection, blood entering through the mitral valve also interacts with residual ow from preceding cycles. The clinical and physiological consequences of these uid dynamics and interactions remain poorly understood in both healthy and diseased hearts. Simulation and imaging studies have aimed to understand the role of intraventricular ow dynamics to facilitate lling, increase ejection e ciency, and avoid blood stasis inside the ventricular chamber. Moreover, these three aspects may be of key importance in patients with heart disease, and most prevalently dilated cardiomyopathy (DCM). In this thesis, we used in vivo measurement of ow in healthy and diseased hearts. A novel processing of Doppler-echocardiography data was performed on patients with DCM and healthy volunteers. Bi-directional velocity eld maps in the apical long axis were obtained and used to perform Lagrangian analysis of transport inside the LV. Lagrangian coherent structures (LCSs) were shown to reveal the boundaries of blood injected and ejected from the heart over multiple beats. These boundaries were used to quantify stasis in the LV, which has potential clinical importance for diagnosing pumping de ciency and thrombosis risk. Indeed, we show that repelling LCSs, in addition to revealing a schematic of the transport topology, also identify structures in the ow that may potentially in uence platelet activation, which we demonstrate on an idealized stenosis model for simplicity. The LCS framework also enabled improved characterization of LV vortices, which had previously received much attention using Eulerian characterizations. The Lagrangian framework presented here uncovered well-de ned boundaries to both E-wave and A-wave lling vortices, which have not been previously quanti ed. To validate the utility xii of the planar ow approximation imposed by Doppler-echocardiography in enabling the dominant transport processes to be characterized, two di erent sets of 3D phase contrast magnetic resonance imaging (PCMRI) data were used to compare 3D ow analysis results with results derived from 2D projection of data in the long-axis. The validation results indicated that the main transport structures were preserved in 2D projections, especially during the ejection phase. Analysis of LV ow topology was also performed in patients undergoing cardiac resynchronization therapy (CRT). The results of this study can contribute to the optimization of AV delays in these patients by taking the LV transport into account. xiii
PH.D in Mechanical Engineering, December 2013
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