Additive manufacturing technology has broadened the ability to customize medical implants, enabling surgeons to equip patients with devices tailored to patient-specific needs. Researchers have applied this manufacturing approach to the design of transcatheter aortic valves, which must be perfectly sized to prevent leaks or dislodgment once inserted.

A new 3D printing workflow allows cardiologists to gauge how different valve sizes will interact with each patient’s unique anatomy before the medical procedure is actually performed. Physical models of individual patients’ aortic valves are produced using CT scan data, and a “sizer” device determines the optimal replacement valve size.

The outer wall of the aorta and associated calcified deposits are easily seen on a CT scan, but the leaflets of tissue that open and close the valve are often too thin to be sufficiently visualized. Software designed to address this limitation uses parametric modeling to generate virtual 3D models of the leaflets using seven A custom sizer device is placed inside each 3D-printed heart valve model and expanded until the proper fit is achieved. Source: Wyss Institute at Harvard UniversityA custom sizer device is placed inside each 3D-printed heart valve model and expanded until the proper fit is achieved. Source: Wyss Institute at Harvard Universitycoordinates on each patient’s valve that are visible on CT scans. The digital models are then merged with the CT data and adjusted to properly fit into the valve. The resulting model is 3D printed into a physical multi-material model.

Next, a 3D-printed custom sizer device is placed inside the printed valve model, expanding and contracting to determine what size artificial valve would best fit each patient. The device is wrapped with a thin layer of pressure-sensing film to map pressure between the sizer and the 3D-printed valves and associated calcified deposits. The multi-material design of the printed valve models, which incorporate flexible leaflets and rigid calcified deposits into a fully integrated shape, more accurately mimics the behavior of real heart valves during artificial valve deployment and provides haptic feedback as the sizer is expanded.

The system was tested against data from 30 patients who had already undergone transcatheter aortic valve replacement; 15 had developed leaks from valves that were too small. The researchers predicted, based on how well the sizer fit into the 3D-printed models of their aortic valves, what size valve each patient should have received, and whether they would experience leaks after the procedure. The system successfully predicted leak outcomes in 60% to 73% of the patients and determined that 60% of the patients had received the appropriate size of valve.

Scientists from Harvard Medical School, Massachusetts General Hospital, Brigham and Women's Hospital, University of Washington Medical Center, Max Planck Institute of Colloids and Interfaces (Germany), Harvard University, University of Washington and VA Puget Sound Health Care System contributed to this study, which is published in the Journal of Cardiovascular Computed Tomography.

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