Sudden cardiac death represents one of the leading causes of death worldwide, with the majority of these deaths caused by arrhythmias derived from ischæmic events. However, the mechanisms leading from ischæmia to re-entry, arrhythmia and eventual death are poorly understood. Furthermore, variability in the action potential of cardiac tissue, while important in determining arrhythmic risk, is only recently being addressed in computational modelling, with little known about the causes and mechanisms underlying it, nor regarding its evolution in response to pathological conditions such as ischæmia. This dissertation investigates the causes of variability in the repolarisation of the action potential of the rabbit ventricular myocyte, and the response of this variability to ischæmia. The effect of variability in ion channel conductances is investigated by means of a complete search of the parameter space revealed by simultaneous variation in multiple parameters describing ion channel conductances in computational models of the rabbit ventricular action potential. Rabbit data and models are used in this thesis due to the similarities to human data, both in terms of electrophysiology generally, and the response to ischæmia specifically. The response of two different model frameworks is assessed to determine similarities and differences between model frameworks that are designed to reproduce the same system. Those models producing action potential durations that fall within an experimentally derived range at multiple pacing rates are used to define model populations that thus reproduce experimental variability in repolarisation. These model populations are used to investigate the effects of ischæmic conditions on population variability. Variability is measured not only for action potential duration, but also for other biomarkers commonly implicated in the development of re-entry. The work presented in this dissertation is significant for: (1) presenting a comprehensive study of the effect of simultaneous variation in ion channel conductances, with details regarding the interactions between conductances and how these interactions change depending on the pacing rate; (2) detailed examination of the differences between two models of the same system; (3) production of the largest extant populations reproducing experimentally observed variability in action potential duration; (4) the first time model populations have been used to investigate the effects of ischæmia on variability.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:655115 |
| Date | January 2014 |
| Creators | Gemmell, Philip Macdonald |
| Contributors | Rodriguez, Blanca; Burrage, Kevin; Quinn, T. Alexander |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:dfa89873-abf9-4486-bc9f-dad9f41321fb |
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