Image-based finite element modelling of fetal critical aortic stenosis with evolving hypoplastic left heart syndrome and fetal aortic valvuloplasty intervention
File(s)
Author(s)
Green, Laura Elizabeth
Type
Thesis
Abstract
Fetal critical aortic stenosis with evolving hypoplastic left heart syndrome (CAS-eHLHS) is a mid-gestation cardiac malformation. CAS-eHLHS has a high likelihood of progressing to hypoplastic left heart syndrome (HLHS), where the neonate will require complex surgeries or a heart transplant. Fetal aortic valvuloplasty (FAV) is an in-utero catheter-based intervention, performed on mid-gestation CAS-eHLHS fetal hearts, which aims to widen the stenotic aortic valve, to prevent a HLHS outcome. However, some patients still progress to a HLHS outcome post-FAV, suggesting that it is clinically difficult to predict FAV outcomes. There is also limited understanding of the biomechanical implications of CAS-eHLHS and FAV. Therefore, it was proposed to use finite element (FE) modelling to address such issues.
FE methods were developed to support later work. This included calibrating the fetal lumped parameter model, investigating the effect of helix angle configuration on fetal LV function (helix angle configuration describes the orientation of the LV myofibers relative to the short-axis plane), to support future assignment of the parameter, and developing an optimisation algorithm, for patient specific computational modelling.
FE analysis showed CAS-eHLHS patients to have compromised functionality. Interestingly, peak systolic myofiber stress, output from the computational methods, showed a unique ability in predicting post-FAV outcomes. A simplified equation was derived for real-time estimation of peak systolic myofiber stress, which upheld its predictive capabilities when tested.
Virtual FAV demonstrated how FAV can partially restore several physiological features towards healthy levels, however, the inclusion of aortic valve regurgitation, in the analysis, compromised LV and left atrium depressurisation but promoted increased stroke volume. Furthermore, patient specific post-FAV modelling enabled analysis of acute FAV outcomes.
Overall, the research improved understanding of the biomechanical implications of CAS-eHLHS and FAV and gave a sense of which cases are more suitable for FAV, which, with future work, could support patient selection.
FE methods were developed to support later work. This included calibrating the fetal lumped parameter model, investigating the effect of helix angle configuration on fetal LV function (helix angle configuration describes the orientation of the LV myofibers relative to the short-axis plane), to support future assignment of the parameter, and developing an optimisation algorithm, for patient specific computational modelling.
FE analysis showed CAS-eHLHS patients to have compromised functionality. Interestingly, peak systolic myofiber stress, output from the computational methods, showed a unique ability in predicting post-FAV outcomes. A simplified equation was derived for real-time estimation of peak systolic myofiber stress, which upheld its predictive capabilities when tested.
Virtual FAV demonstrated how FAV can partially restore several physiological features towards healthy levels, however, the inclusion of aortic valve regurgitation, in the analysis, compromised LV and left atrium depressurisation but promoted increased stroke volume. Furthermore, patient specific post-FAV modelling enabled analysis of acute FAV outcomes.
Overall, the research improved understanding of the biomechanical implications of CAS-eHLHS and FAV and gave a sense of which cases are more suitable for FAV, which, with future work, could support patient selection.
Version
Open Access
Date Issued
2023-10
Date Awarded
2024-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Yap, Choon Hwai
Publisher Department
Bioengineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)