Wave Intensity Analysis In Coronary Vessels
: A Biophysical Framework For Simulation And Analysis

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Coronary wave intensity analysis (cWIA) is uniquely suitable for the investigation of coronary hemodynamics due to its capability of distinguishing, in the time domain, between proximal and distal influences on coronary blood. cWIA showed its potential in the research settings and the cWIA-derived metrics recently demonstrated prognostic value.

Two main limitations ascribable to cWIA are currently hampering its clinical application. Firstly, cWIA methodology has to become standardised, removing the operator bias, to enable multi-centre trials. Secondly, the mechanistic link between the left ventricular (LV) dynamics and the cWIA profile has to be elucidated to understand the origin of the cWIA waves. Both these objectives are addressed in this thesis, integrating patient data with coronary blood flow modelling techniques.

Initially, we demonstrated that temporal alignment and filtering of the acquired pressure and velocity waveforms have a strong impact on the cWIA-metrics. Consequently, a novel algorithm making cWIA standardised, robust, accurate and fully automatic was developed. The algorithm performances were extensively tested by means of in-silico and in-vivo data.

To elucidate the impact that bifurcation morphology has on wave propagation, a new theoretical framework was introduced and validated, by means of ex-vivo high-resolution cryomicrotome data of animal and human vasculatures. This enabled a detailed description of the branching pattern of the coronary vasculature and the demonstration that the coronary bifurcations are well-matched (no reflection) for forward traveling waves. Furthermore, we demonstrated that assuming constant material properties through the coronary vasculature to parametrise one-dimensional model of coronary blood flow agrees with the experimental data automatically providing well-matchedness.

Finally, to investigate the origin of the cWIA profile, in-vivo simultaneous measurements of LV and coronary hemodynamics were acquired enabling an accurate description of the timing and correlation between the PV-loop metrics and the cWIA metrics. Furthermore, these measurements were used to validate a computational model based on the 1D wave propagation theory. The model was then used to generate a wide dataset (3000) of in-silico patients to then build a metamodel of the mechanistic model providing a unique description of the LV-coronary coupling. In fact, not only the mechanisms driving each wave of the cWIA profile were precisely delineated but novel cWIA-derived indices (FCW and BCW) of LV contractility and myocardial energetics were demonstrated.
Date of Award1 Nov 2015
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorNicolas Smith (Supervisor) & Jack Lee (Supervisor)

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