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Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient
Thesis (MEng)--Stellenbosch University, 2024.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613858694168576 |
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| access_status_str | Open Access |
| author | Marais, Eugéne Claude |
| author2 | Venter, Martin Philip |
| author_browse | Marais, Eugéne Claude Venter, Martin Philip |
| author_facet | Venter, Martin Philip Marais, Eugéne Claude |
| author_sort | Marais, Eugéne Claude |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131820 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:42:49.487Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131820 Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient Marais, Eugéne Claude Venter, Martin Philip Laubscher, Ryno Herbst, Phillip Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. Aortic valve -- Diseases Cardiovascular system -- Diseases Heart valves -- Mechanical properties Finite element method UCTD Thesis (MEng)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Cardiovascular disease remains a significant global burden, accounting for approximately 32 % of all deaths worldwide. This impact is particularly severe in impoverished regions, such as Sub-Saharan Africa, where inadequate medical infrastructure has led to a higher prevalence of these conditions among younger demographics. By contrast, in high-income countries, older populations are more commonly affected. A prevalent valvular disease in sub-Saharan Africa is rheumatic heart disease, which arises from untreated rheumatic fever. Under these conditions, bacteria attack the aortic valve, leading to stenosis and death. Notably, 61 % of all valvular disease fatalities are attributed to aortic valve failure, highlighting the importance of this valve. Non-invasive diagnostic tools are essential to better understand aortic valve function and provide patient-specific care. Computational simulations are at the forefront of these tools, with lumped parameter models proving particularly effective for their ability to study both local and global haemodynamics simultaneously. However, these models often simplify the aortic valve's kinematic behaviours and material properties. This thesis aims to investigate the effect of leaflet motion and aortic valve flexure on the cardiovascular system's haemodynamics. This was achieved by integrating a three-dimensional finite element surrogate model of an aortic valve into a lumped-parameter model, replacing the existing simplified valve representation. The integration was accomplished using a machine learning algorithm. Two case studies were undertaken, comparing outcomes between a healthy valve and a moderately stenosed valve. When comparing the newly formed simplified fluid structure interaction model with the zero-dimensional lumped parameter model, which was used to produce the new model, the results indicate that including material properties and stiffness significantly affects local and global haemodynamics. The moderately stenosed valve model predicted mean pressure drops that aligned well with clinical studies, whereas the lumped parameter model underestimated these pressure drops. Synthetic experimental valves, replicating the finite element models, were produced and tested under steady and pulsatile flow conditions to further explore the valve dynamics. The steady flow experiments demonstrated a good correlation between the experimental and finite element models when comparing the area openings of the valves. However, during dynamic testing, the finite element models struggled to capture the full range of the valve dynamics. Specifically, they overestimated the valve opening and closure times, with healthy valves opening 75 % faster and stenosed valves 90 % faster. Although the stenosed valves fell within 67 % of the area predicted by the experimental valves during the systole cycle and the healthy valves predicted peak valve area openings approximately 7.1 % greater than the experimental valves, both case studies still failed to capture the dynamics of the valve opening and closure accurately. The results suggest that while the simplified fluid-structure interaction model holds promise as an improved approach for lumped parameter model replacement, the dynamic results highlight the need for a full fluid–structure interaction model to study valve dynamics accurately. Despite these challenges, the coupling approach shows potential, particularly for diagnostic tools that target stenosed valves. AFRIKAANSE OPSOMMING: Kardiovaskulêresiekte bly 'n beduidende wêreldwye las en is verantwoordelik vir ongeveer 32 % van alle sterftes wêreldwyd. Hierdie impak is veral ernstig in arm streke, soos Sub-Sahara Afrika, waar onvoldoende mediese infrastruktuur gelei het tot 'n hoër voorkoms van hierdie toestande onder jonger bevolkingsgroepe. In teenstelling hiermee word ouer bevolkings in hoë-inkomste lande meer algemeen geraak. ’n Algemene klepsiekte in Sub-Sahara Afrika is rumatiese hartsiekte, wat voortspruit uit onbehandelde rumatiekkoors. Onder hierdie toestande val bakterieë die aortaklep aan, wat tot stenose en dood lei. Opmerklik is dat 61 % van alle sterftes as gevolg van klepsiektes toegeskryf kan word aan aortaklepversaking, wat die belangrikheid van hierdie klep beklemtoon. Nie-indringende diagnostiese hulpmiddels is noodsaaklik om aortaklepfunksie beter te verstaan en pasiëntspesifieke sorg te bied. Rekenaargebaseerde simulasies is aan die voorpunt van hierdie hulpmiddels, met enkelvoudige parametermodelle wat uitstaan vir hul vermoë om beide lokale en globale hemodinamika gelyktydig te bestudeer. Hierdie modelle vereenvoudig egter dikwels die aortaklep se kinematiese gedrag en materiaaleienskappe. Hierdie tesis poog om die effek van klepbladbeweging en aortaklepbuiging op die kardiovaskulêre stelsel se hemodinamika te ondersoek. Dit is bereik deur die integrasie van 'n drie-dimensionele eindige element surrogaatmodel van 'n aortaklep in 'n enkelvoudige parametermodel, wat die bestaande vereenvoudigde klepvoorstelling vervang. Die integrasie is bewerkstellig deur middel van 'n masjienleer-algoritme. Twee gevallestudies is onderneem, wat uitkomste tussen 'n gesonde klep en 'n matig stenoseerde klep vergelyk. Wanneer die nuutgevormde vereenvoudigde vloeistruktuur-interaksiemodel vergelyk word met die nul-dimensionele enkelvoudige parametermodel, wat gebruik is om die nuwe model te produseer, dui die resultate daarop dat die insluiting van materiaaleienskappe en styfheid plaaslike en globale hemodinamika beduidend beïnvloed. Die matig stenotiese klepmodelle het gemiddelde drukvalle voorspel wat goed ooreenstem met kliniese studies, terwyl die enkelvoudige parametermodel hierdie drukvalle onderskat het. Eksperimentele kleppe wat die eindige elementmodelle namaak, is vervaardig en onder konstante en polsende vloeitoestande getoets om die klepdinamika verder te ondersoek. Die konstante vloeitoetse het 'n goeie korrelasie tussen die eksperimentele en eindige elementmodelle getoon. Tydens dinamiese toetsing het die eindige elementmodelle egter gesukkel om die volle omvang van die klepdinamika vas te vang. Spesifiek het hulle die klep se oopmaak- en sluittye oorskat, met gesonde kleppe wat 75 % vinniger oopmaak en stenotiese kleppe 90 % vinniger. Alhoewel die stenotiese kleppe binne 67 % van die area wat deur die eksperimentele kleppe voorspel is, geval het gedurende die sistool-siklus, en die gesonde kleppe piekkleparea-openings voorspel het wat ongeveer 7.1 % groter was as die eksperimentele kleppe, het albei gevallestudies steeds nie daarin geslaag om die dinamika van die klep se oopmaak en sluiting akkuraat vas te vang nie. Die resultate dui daarop dat, hoewel die vereenvoudigde vloeistruktuur-interaksiemodel belowend is as 'n verbeterde benadering vir vervanging van die enkelvoudige parametermodel, die dinamiese resultate die behoefte beklemtoon vir 'n volledige vloeistruktuur-interaksiemodel om die klepdinamika akkuraat te bestudeer. Ten spyte van hierdie uitdagings toon die koppelingbenadering potensiaal, veral vir diagnostiese hulpmiddels wat gemik is op stenotiese kleppe. Masters 2025-03-31T09:10:26Z 2025-03-31T09:10:26Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131820 Stellenbosch University xiv, 98 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Aortic valve -- Diseases Cardiovascular system -- Diseases Heart valves -- Mechanical properties Finite element method UCTD Marais, Eugéne Claude Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient |
| title | Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient |
| title_full | Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient |
| title_fullStr | Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient |
| title_full_unstemmed | Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient |
| title_short | Using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient |
| title_sort | using numerical modelling and experimental approaches to study the effect of dynamic valve deformations on aortic transvalvular pressure gradient |
| topic | Aortic valve -- Diseases Cardiovascular system -- Diseases Heart valves -- Mechanical properties Finite element method UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131820 |
| work_keys_str_mv | AT maraiseugeneclaude usingnumericalmodellingandexperimentalapproachestostudytheeffectofdynamicvalvedeformationsonaortictransvalvularpressuregradient |