Surgical management of ischemic mitral regurgitation: an in-vitro investigation

Owing to its complex structure and dynamic loading, surgical repair of the heart’s mitral valve poses a significant clinical burden. Specifically, repair of ischemic mitral regurgitation, which is caused by the geometric disruption of the mitral apparatus in the setting of ventricular dysfunction, results in poor long-term patient survival. Clinical data have shown that the preferred surgical treatment, restrictive mitral annuloplasty, may result in 15-30% early (< 6 months) recurrence of mitral regurgitation; this may exceed 70% after five years. Studies have suggested that isolated annuloplasty may not be a comprehensive repair suitable for all patients because ischemic pathology is multi-factorial and results in variable ventricular and valvular geometric distortions. Therefore, in this thesis, a new surgical planning paradigm was developed through three specific aims. In specific aim 1, in collaboration with Philips Healthcare, a novel tool to more accurately and quantitatively assess mitral valve insufficiency was developed and rigorously validated using the Georgia Tech Left Heart Simulator. This tool was found to be more efficacious and robust than the current clinical standard. Ultimately, this improved diagnostics may better inform surgical indication, specifically, to identify patients that may not benefit from simple ring annuloplasty. In specific aim 2, targeted adjunctive surgical repair for such patients were investigated. Anterior leaflet augmentation and basal papillary muscle relocation were observed to restore mitral valve function while reducing the leaflet-subvalvular tethering associated with ischemic left ventricular remodeling. These efficacious repairs were found to be robust to variability in surgical implementation, which may encourage more widespread clinical adaptation. Finally, in specific aim 3, an integrative experimental framework was developed to promote pre-operative patient specific evaluation of mitral valve surgical repair using novel computational methods. The experimental framework combined high-resolution state of the art imaging with clinical imaging to provide the most realistic anatomical reconstructions possible. For the first time, ventricular flow fields through and proximal to a native mitral valve were acquired using stereoscopic particle image velocimetry. These data were combined with measurements of leaflet dynamics and subvalvular forces to create a comprehensive database for the rigorous validation of mitral valve finite element and fluid-structure interaction models. Collectively, these studies comprise a surgical planning paradigm that may better inform repair of mitral valve insufficiency.Ph.D

A high-fidelity and micro-anatomically accurate 3D finite element model for simulations of functional mitral valve

Promising mitral valve (MV) repair concepts include leaflet augmentation and saddle shaped annuloplasty, and recent long-term studies have indicated that excessive tissue stress and the resulting strain-induced tissue failure are important etiologic factors leading to the recurrence of significant MR after repair. In the present work, we are aiming at developing a high-fidelity computational framework, incorporating detailed collagen fiber architecture, accurate constitutive models for soft valve tissues, and micro-anatomically accurate valvular geometry, for simulations of functional mitral valves which allows us to investigate the organ-level mechanical responses due to physiological loadings. This computational tools also provides a means, with some extension in the future, to help the understanding of the connection between the repair-induced altered stresses/strains and valve functions, and ultimately to aid in the optimal design of MV repair procedure with better performance and durability.</p

A high fidelity, micro-structural and anatomically accurate 3D finite element model for functioning heart mitral valve

Many surgeons have come to view mitral valve (MV) repair as the treatment of choice in patients with mitral regurgitation (MR) [1]. However, recent long-term studies have indicated that the recurrence of significant MR after repair may be much higher than previously believed, particularly in patients with (ischemic mitral regurgitation) IMR [2]. Since a significant number of these failures result from chordal, leaflet and suture line disruption, it has been suggested that excessive tissue stress and the resulting strain-induced tissue damage are important etiologic factors. We thus hypothesize that the restoration of homeostatic normal MV leaflet tissue stress levels in IMR repair techniques ultimately leads to improved repair durability through restoration of normal MV responses. Therefore, the objective of this study is to develop a novel high-fidelity and micro-anatomically accurate 3D finite element (FE) model that incorporates detailed collagen fiber architecture, realistic constitutive models, and micro-anatomically accurate valvular geometry to connect the cellular function of the MV tissues with the organ level mechanical responses, and to aid in the design of MV repair procedures

Data Acquisition Mechanical Simulator

Most common form of valvular heart disease Significant mortality &amp; morbidity rates Traditional treatment: MV replacemen

A high-fidelity and micro-anatomically accurate 3D finite element model for simulations of functional mitral valve

Promising mitral valve (MV) repair concepts include leaflet augmentation and saddle shaped annuloplasty, and recent long-term studies have indicated that excessive tissue stress and the resulting strain-induced tissue failure are important etiologic factors leading to the recurrence of significant MR after repair. In the present work, we are aiming at developing a high-fidelity computational framework, incorporating detailed collagen fiber architecture, accurate constitutive models for soft valve tissues, and micro-anatomically accurate valvular geometry, for simulations of functional mitral valves which allows us to investigate the organ-level mechanical responses due to physiological loadings. This computational tools also provides a means, with some extension in the future, to help the understanding of the connection between the repair-induced altered stresses/strains and valve functions, and ultimately to aid in the optimal design of MV repair procedure with better performance and durability