A computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardium

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dc.contributor.advisorFranz, Thomasen_ZA
dc.contributor.advisorDavies, Neilen_ZA
dc.contributor.authorMiller, Reneeen_ZA
dc.date.accessioned2014-07-28T18:17:31Z
dc.date.available2014-07-28T18:17:31Z
dc.date.issued2012en_ZA
dc.descriptionIncludes abstract.
dc.descriptionIncludes bibliographical references.
dc.description.abstractCardiovascular diseases account for one third of all deaths worldwide, more than 33% of which are related to ischaemic heart disease, involving a myocardial infarction (MI). Emerging MI therapies involving biomaterial injections have shown some benefits; the underlying mechanisms of which remain unclear. Computational models offer considerable potential to study the biomechanics of a myocardial infarction and novel therapies. Geometrical data of a healthy human left ventricle (LV) obtained from magnetic resonance images (MRI) was used to create a finite element (FE) mesh of the LV at the end-systolic time point using Continuity® 6.3 (University of California in San Diego, US). A mesh of 96 hexahedral elements with high order basis functions was employed to adequately describe the geometry of the LV. Simulations of diastolic filling and systolic contraction were performed using a transversely isotropic exponential strain energy function and a model for active stress based on contraction at the cellular level. An anterior apical, transmural MI was modelled in the LV encompassing 16% of the LV wall volume. The infarct was modelled at acute and fibrotic stages of post-infarct LV remodelling by altering the constitutive and active stress models to best describe passive and active behaviour of the ischaemic myocardium at each time point. The geometry of the LV with the fibrotic infarct was adjusted to represent the wall thinning that occurs during LV post-MI remodelling. Hydrogel injection was modelled as layers with material properties differing from those of the surrounding myocardium while accounting for thickening of the LV wall at the injection site. The study design comprised a healthy case and two infarcted cases with and without hydrogel injection. The end-diastolic volume (EDV) increased in the acute infarct model compared to the healthy case due to the reduced stiffness in the infarct wall. An EDV increase was not observed in the fibrotic infarct model compared to the healthy case. This was partially attributed to the increase in infarct stiffness and partially due to the fact that remodelling-related dilation of the LV was not implemented in the model. Inclusion of hydrogel lowered EDV in both the acute and fibrotic models. The predicted ejection fraction (EF) decreased from 41.2% for the healthy case to 28.5% and 33.0% for the acute and fibrotic infarct models, respectively. Inclusion of hydrogel layers caused an improvement in EF in the acute model only.en_ZA
dc.identifier.apacitationMiller, R. (2012). <i>A computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardium</i>. (Thesis). University of Cape Town ,Faculty of Health Sciences ,Department of Human Biology. Retrieved from http://hdl.handle.net/11427/3269en_ZA
dc.identifier.chicagocitationMiller, Renee. <i>"A computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardium."</i> Thesis., University of Cape Town ,Faculty of Health Sciences ,Department of Human Biology, 2012. http://hdl.handle.net/11427/3269en_ZA
dc.identifier.citationMiller, R. 2012. A computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardium. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Miller, Renee AB - Cardiovascular diseases account for one third of all deaths worldwide, more than 33% of which are related to ischaemic heart disease, involving a myocardial infarction (MI). Emerging MI therapies involving biomaterial injections have shown some benefits; the underlying mechanisms of which remain unclear. Computational models offer considerable potential to study the biomechanics of a myocardial infarction and novel therapies. Geometrical data of a healthy human left ventricle (LV) obtained from magnetic resonance images (MRI) was used to create a finite element (FE) mesh of the LV at the end-systolic time point using Continuity® 6.3 (University of California in San Diego, US). A mesh of 96 hexahedral elements with high order basis functions was employed to adequately describe the geometry of the LV. Simulations of diastolic filling and systolic contraction were performed using a transversely isotropic exponential strain energy function and a model for active stress based on contraction at the cellular level. An anterior apical, transmural MI was modelled in the LV encompassing 16% of the LV wall volume. The infarct was modelled at acute and fibrotic stages of post-infarct LV remodelling by altering the constitutive and active stress models to best describe passive and active behaviour of the ischaemic myocardium at each time point. The geometry of the LV with the fibrotic infarct was adjusted to represent the wall thinning that occurs during LV post-MI remodelling. Hydrogel injection was modelled as layers with material properties differing from those of the surrounding myocardium while accounting for thickening of the LV wall at the injection site. The study design comprised a healthy case and two infarcted cases with and without hydrogel injection. The end-diastolic volume (EDV) increased in the acute infarct model compared to the healthy case due to the reduced stiffness in the infarct wall. An EDV increase was not observed in the fibrotic infarct model compared to the healthy case. This was partially attributed to the increase in infarct stiffness and partially due to the fact that remodelling-related dilation of the LV was not implemented in the model. Inclusion of hydrogel lowered EDV in both the acute and fibrotic models. The predicted ejection fraction (EF) decreased from 41.2% for the healthy case to 28.5% and 33.0% for the acute and fibrotic infarct models, respectively. Inclusion of hydrogel layers caused an improvement in EF in the acute model only. DA - 2012 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2012 T1 - A computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardium TI - A computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardium UR - http://hdl.handle.net/11427/3269 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/3269
dc.identifier.vancouvercitationMiller R. A computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardium. [Thesis]. University of Cape Town ,Faculty of Health Sciences ,Department of Human Biology, 2012 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/3269en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Human Biologyen_ZA
dc.publisher.facultyFaculty of Health Sciencesen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherMedicineen_ZA
dc.titleA computational study of post-infarct mechanical effects of injected biomaterial into ischaemic myocardiumen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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