Computational Modeling of Heart Valves for Surgical Planning
Surgical repair of heart valves is difficult due to the complex anatomy and properties of the valve structures. We aim to develop the technology to enable surgeons to use computer simulation to plan the surgical repair of heart valves. We have developed fast and biomechanically accurate computational models of both mitral and aortic valves and used them to study issues relevant to the surgical repair of valves.
We have used the finite element model of heart valve leaflets to study a common surgical strategy for reconstructing damaged aortic valve leaflets using tissue harvested from the patient’s own pericardium . It is difficult for surgeons to determine the size and shape of the leaflet graft in order to achieve a satisfactory repair. We simulated closure of the repaired valve for a range of graft sizes and found optimal valve function with a graft that is approximately 25% wider and 25% wider than the native valve leaflets. This oversizing of the graft is necessary to compensate for the decreased distensibility of the pericardium relative to native valve tissue.
Researchers: Peter Hammer, Douglas Perrin and Neil A. Tenenholtz
Surgical Planning for Mitral Valve Repair
Accelerating the computational valve model, valve mechanics can be simulated at haptic rates, allowing for real-time user interaction. This permits both the assessment of a valve’s structure and the virtual implementation of a repair strategy in a manner that is intuitive and interactive. When combined with a patient-specific valve model, such as one generated through advanced ultrasound segmentation, the platform can be used for preoperative planning and case-specific surgeon training.
Mitral valve repair is hard. Very hard. Although it’s the most effective technique for eliminating mitral regurgitation, this procedure can be challenging for even experienced cardiac surgeons. In addition to the difficulties presented by a limited intraoperative field of view, currently, the heart must be stopped in nearly all procedures. As a result, the surgeon is unable to observe the precise effects of the implemented repair and instead must predict the closed valve shape using past experience as a guide. Consequently, surgeons who perform fewer operations in a given year are significantly more likely to replace the valve with a prosthetic, a simpler technique known to have clinically inferior results, rather than repair it.
A surgical planner with a physically accurate tissue model, such as the system we have developed, ameliorates this situation by allowing the surgeon to virtually implement a variety of candidate procedures and then visualize and evaluate post-repair valve function. With a patient-specific valve model and a Sensable PHANTOM Desktop, the user is able to interact in real-time with the virtual valve. While this necessitates a 1 kHz update rate for smooth user-model interaction, using a mass-spring tissue membrane model, we are able to simulate valve mechanics at haptic rates. Together, this enables not only the testing of various repair techniques but also the evaluation of the valve pathology.
Researchers: Peter Hammer, Neil A. Teneholtz, Nikolay V. Vasilyev, and Robert J. Schneider
