While advances in cardiac surgery have revolutionized the treatment of heart valve disease, problems remain with the durability of surgical repair techniques, devices and replacement valves. A major challenge in perfecting the design of these procedures and devices is to ensure that post-operatively the valve functions under the lowest possible stress to ensure its longevity. This is particularly true for the mitral valve, which faces the highest pressures and forces of the four cardiac valves. The force is equal to two regular bottles of water in gravity, 100,000 timers per day. The seriousness of the problem is dire; according to the 2017 American Heart Association reports, recurrence of moderate to severe insufficiency at 12 months following surgical repair of ischemic mitral valve regurgitation is still more than 30%. While information for surgical planning or device design can be based on computer simulations built from available medical imaging modalities with assumed or measured material properties of the heart and valve tissue, these material properties are often associated with significant simplifications and thus the simulation may not accurately reflect the true forces and strains on the cardiac valves. The goal of this work is to create a new, force-validated model of the mitral valve for patient-specific surgical planning and intelligent device development, using nature?s own stress-minimization concepts. We hypothesize that computational soft tissue models that are coupled with experimental shape and force measurements obtained directly from a functioning valve will lead to a better validated system for stress-optimized heart valve interventions. The porcine mitral valve has for more than two decades been accepted as a highly relevant anatomic basis of the human mitral valve. Within this project, we will image porcine hearts in a sedated animal to obtain the geometry of major valve landmark points, then explant the heart and mount the dissected mitral valve in a valve holder that is 3D printed to match each animal?s individual anatomy. The mitral valve will then undergo high resolution magnetic resonance imaging within a pressurized chamber that will allow the valve to remain open and closed under physiological conditions. Detailed force measurements will be performed on the same valve to ensure that correct biomechanical boundary conditions are obtained. These high-resolution data will then inform a computational model of the valve that will be tested and validated against the clinical measurements obtained in vivo prior to heart explantation. At the conclusion of this project we aim to employ the newly developed model in one exemplary mitral valve repair surgery to demonstrate the significant advantage of force validated computational models. The project participants? competencies are interdisciplinary and highly relevant to the project. Expertise is brought together from in vivo and in vitro biomechanical cardiovascular experimentation, high fidelity MRI imaging of soft tissues, and computational modeling of cardiovascular tissue and the mitral valve.
While advances in cardiac surgery have revolutionized the treatment of heart valve disease, problems associated with the long-term performance of surgical repair techniques and replacement valves are still prevalent. The goal of this work is to create a new, force-validated model of the mitral valve for intelligent surgery planning and device development, using nature?s own stress-minimization concepts for maximum longevity of mitral valve interventions. Mitral valves will be imaged in vivo in a porcine model, subsequently explanted for testing in a 3D-printed patient-specific anatomically and physiologically accurate chamber; and the data will be used in a computational soft tissue model for optimal relevancy of stress conditions in the left heart.
