Stent Design for the Left Ventricle
Yale Senior Thesis: The Design and Analysis of a Nitinol Mesh Stent-Like Device to Reduce Functional Mitral Regurgitation and Encourage Left Ventricular Remodeling
Mitral Regurgitation (MR), or the inability of the mitral valve to collapse fully and prevent the backwards leakage of blood, is a prevalent condition in the US population, occurring in 1 out of 10 persons greater than the age of 75.3,4 Such a condition causes the abnormal backflow of blood into the left atrium, creating unbalanced stress in the myocardium as well as on the pulmonary veins. This can lead to dangerous, often fatal consequences for those left untreated, including atrial fibrillation and heart failure.
Despite the negative effects of MR – further exemplified by the condition’s estimated mortality rate of 57% only a single year after diagnosis1 – half of patients are never recommended for surgical correction.2 The typical MR patient is elderly, with other comorbidities to consider; so, many physicians refuse to prescribe intervention given the risk. Mitral regurgitation, however, can significantly reduce the quality of life for those diagnosed, causing unceasing shortness of breath (dyspnea) and fatigue.5
Functional MR (fMR), also known as secondary MR, is a specific class of mitral regurgitation caused by non-valvular elements. The standard of care for mitigating fMR is open-heart surgery. Although one minimally-invasive device, Abbott’s MitraClip, has been approved for treating fMR, clinical results were disproportionate across patient types and some showed no difference than control subjects – likely due to its one-size-fits-all approach.6 Plenty of other devices have failed in clinical trials. Given our country’s aging population and the high mortality rate of this condition, it is essential that additional, more flexible devices be developed which have widespread positive impacts on patient life.
My senior capstone for the Yale BME Department shows the creation and testing of a nitinol-based medical device to combat functional Mitral Regurgitation, targeting patients with a dilated left ventricle. Based on input from physicians and clinicians as well as prior art, a preliminary design was outlined and fabricated in computer-aided design software. Simultaneously, the left ventricular anatomy was studied in fMR patients and measurements of feature data were gathered. Lastly, finite element analysis (in Abaqus CAE) was performed on variations of the basic design to test device longevity, compatibility, and reaction to the forces of the heart. Although numerous additional steps must be taken before a design is released for preclinical testing, this research forms the backbone of the effort to bring a more adaptable, minimally-invasive option for treating fMR patients. I cannot include the actual thesis for IP reasons, but I have added pictures on this page.
Above I have shown a design framework for design of the left ventricle device.
Above is a simplified model of the left ventricle with physiologically-accurate components derived from patient data.
Lastly, this is an image of a portion of the simulation results; see the bar on the side for an indication of high vs low stress on the stent body.
You can check out my GitHub Repo, anushamanglik/nitinol-heart-stent-design for more details on the simulations. As of now this is only open to my laboratory’s researchers; please let me know by email if you’d like access.