Why Polymer Heart Valves Could Outlast the Real Thing
When doctors began replacing faulty aortic valves through a catheter threaded into an artery instead of cracking open a patient's chest, it marked a revelation for elderly patients too frail for surgery. The minimally-invasive approach, called TAVR, introduced an unexpected problem: as younger patients began receiving these valves, engineers realized the tissue-based valves at the heart of the procedure were not built to last decades inside a beating body.
A team at Stony Brook University, funded by the National Institute of Biomedical Imaging and Bioengineering, is betting that polymers hold the answer. Led by Danny Bluestein, a professor of biomedical engineering, the group has designed and tested an experimental TAVR valve made from synthetic material rather than animal tissue—and early results suggest it might actually outperform what surgeons use today.
The Core Issue: Durability
Current TAVR valves are crafted from animal tissue, which degrades over time and can leak. Tissue valves also calcify, which is precisely what causes aortic stenosis in the first place.
Polymer valves, by contrast, can be engineered to maintain their shape and properties indefinitely. Unlike tissues, their shape and properties can be changed, meaning design flaws can be corrected before expensive animal testing ever begins.
To test their prototype—developed in partnership with Polynova Cardiovascular Inc.—the researchers put it through three rigorous trials.
The Three Tests
- Flow Efficiency Test: The team pumped blood-like fluid through the valve at heartbeat rates, measuring the effective orifice area—how wide the valve opens to let blood through. A larger, rounder opening means more efficient pumping. The polymer valve outperformed both the Perimount SAVR valve used in open-heart surgery and the Inovare TAVR valve currently used in minimally-invasive procedures.
- Patient-Specific Anatomy Test: The researchers mounted the valves inside a 3D-printed replica of an actual patient's aorta, reconstructed from CT scans. This patient-specific test introduced the anatomical quirks that complicate real surgeries—slight variations in geometry that can distort how a valve sits and functions. All three valves performed slightly worse in this setup than in the mechanical rig, but the polymer valve still matched or exceeded its competitors.
- Clotting Risk Test: The third test addressed the most dangerous complication: clotting. When blood flows through artificial devices, it can activate platelets, triggering a cascade that leads to dangerous clots and strokes. Patients with implanted valves typically spend the rest of their lives on blood thinners to prevent this—medications with their own risks, including prolonged bleeding and hemorrhagic strokes. The polymer valve showed the lowest platelet activation of the three.
The polymer valve demonstrated superior performance across all three key metrics: flow efficiency, patient-specific anatomical fit, and thrombogenicity (clotting risk). This combination suggests a promising path toward longer-lasting, safer heart valve replacements.
Grace Peng, who directs NIBIB's modeling and simulation program, characterized the work as pioneering in its combination of computer modeling and experimental techniques. The team uses simulations to spot structural problems early, then refines the valve's geometry, flexibility, or composition before moving forward.
Looking Ahead
The researchers caution that this is preliminary work. Durability testing, long-term stability during the compression required to fit a valve into a catheter, and susceptibility to calcium buildup all need more investigation before polymer valves could become a clinical reality.
Based on: "Development and Prospective Testing of a Novel Polymeric TAVR Device"; Danny Bluestein et al.; Stony Brook University / Polynova Cardiovascular Inc.; Annals of Biomedical Engineering, January 2019.