Tens of thousands of patients each year are diagnosed with heart valve disease. TAVR is often considered for patients who are at high risk for complications with an open-heart surgery to replace the valve. But the prosthetic valves are made in a variety of sizes from multiple manufacturers. Leakage occurs when the new valve doesn’t achieve a precise fit and blood flows around the prosthetic rather than through it as intended.
Reduced chance of leakage
The models are created with a special metamaterial design and then made by a multi-material 3-D printer, which gives the researchers control over such design parameters as diameter and curving wavelength of the metamaterial used for printing, to more closely mimic physiological properties of the tissue. For example, the models can recreate conditions such as calcium deposition — a common underlying factor of aortic stenosis — as well as arterial wall stiffness and other unique aspects of a patient’s heart.
That interaction was simulated by embedding wavy, stiff microstructures into the softer material during the 3D printing process. The researchers created heart valve models from medical imaging of 18 patients who had undergone a valve replacement surgery. The models were fitted with dozens of radiopaque beads to help measure the displacement of the tissue-mimicking material.
The researchers then paired those models with the same type and size prosthetic valves that interventional cardiologists had used during each patient’s valve replacement procedure. Inside a warm-water testing environment controlled to maintain human body temperature, the researchers implanted the prosthetics inside the models, being careful to place the new valves in the exact location that was used during the clinical procedure for each case.
Interacting with prosthetics
Those inconsistencies were assigned values that formed a "bulge index," and the researchers found that a higher bulge index was associated with patients who had experienced a higher degree of leakage after valve placement. In addition to predicting the occurrence of the leakage, the 3-D printed models were also able to replicate the location and severity of the complication during the experiments.
The researchers plan to continue to optimize the metamaterial design and 3-D printing process and evaluate the use of the 3-D printed valves as a pre-surgery planning tool, testing a larger number of patient-specific models and looking for ways to further refine their analytic tools.