SBU Researchers Tackle Life-Saving Issues for End-Stage Heart Failure Patients
Innovative Methodology Uses Advanced Simulation, Testing to Evaluate Heart-Saving Devices
STONY BROOK, N.Y., May 5, 2014 – The 7.5 million patients in the United States suffering from end-stage heart failure desperately need a lifeline. One option is a ventricular assist device (VAD), which serves as a “bridge” to a heart transplant and, in long-term use, as “destination therapy,” continuing to support heart function if a transplant is not an option. Researchers at Stony Brook University have developed an innovative technique to evaluate VAD efficacy and safety. Their device thrombogenicity emulation (DTE) methodology uses advanced simulation and testing with human blood to help determine which VADs cause less damage to blood while minimizing or eliminating the risk of blood clotting, stroke, or death.
The VAD is a mechanical pump that takes blood from a lower chamber of the heart and helps pump it to the body and vital organs. It is implanted beside the failing heart; one of its most famous recipients is former U.S. Vice President Dick Cheney. Stony Brook’s DTE methodology assesses which VADs provide a clinical advantage by reducing the medications—with their potential complications—that are used to prevent blood clots.
A study in the Journal of Biomechanical Engineering , “Thromboresistance Comparison of the HeartMate II Ventricular Assist Device With the Device Thrombogenicity Emulation-Optimized HeartAssist 5 VAD,” lays out the findings of their research, which provides crucial data about the operation of a new VAD market entrant.
“The FDA recently approved the designations of the Thoratec HeartMate II ventricular assist device for both bridge-to-transplant and destination therapy, due to its mechanical durability and improved hemodynamics,” says Danny Bluestein, PhD, Professor of Biomedical Engineering in Stony Brook University’s Biomedical Engineering Department, and Principal Investigator for the study. “However, incidence of pump thrombosis and thromboembolic events—blood clots occurring inside a blood vessel—remains high, and the life-long complex pharmacological regimens are mandatory in its VAD recipients.”
The research team compared thrombogenicity in the previously DTE-optimized HeartAssist 5 (formerly the Debakey VAD) with the HeartMate II VAD. Using numerical flow simulations, they extracted and compared the probability density function—the “thrombogenic footprint”—of the stress accumulations of large number of platelets flowing through each device, and measured shear-induced platelet activation rates in recirculating flow loops.
The results indicated that platelets flowing through the DTE-optimized HeartAssist 5 are exposed to significantly lower shear stress accumulations, which lead to platelet activation, than the HeartMate II, especially at the impeller-shroud gap regions. The researchers also reported that thrombus formation patterns observed in the HeartMate II are absent in the HeartAssist 5. Additionally, platelet activation rates (PAR) —measured in vitro with the VADs mounted in recirculation flow loops—show a 2.5-fold significantly higher PAR value for the HeartMate II.
“This head-to-head comparative study for thrombogenic performance of the two VADs—one optimized with the DTE methodology, and one FDA-approved—demonstrates the efficacy of the DTE methodology for drastically reducing a device’s thrombogenic potential,” Bluestein says. “This validates the need for a robust, in silico/in vitro optimization methodology for improving cardiovascular devices thromboresistance.”
The research results and new technology to evaluate the devices are of particular interest to the VAD Program at the Stony Brook University Heart Institute. The VAD Program, the only one of its kind on Long Island, provides destination therapy using the latest VAD technology to treat patients with advanced heart failure.
“LVADs [left ventricular assist devices] provide life-sustaining treatment for many patients with advanced heart failure, and nearly 4,000 LVADs were implanted in the United States last year,” says Hal Skopicki, MD, PhD, Assistant Professor of Medicine and Co-Director of the Stony Brook VAD Program. “Recent data suggest that approximately 10 percent of pumps can become clotted (thrombosis), with a concomitant increase in the risk of death. Dr. Bluestein’s work offers important insights into the mechanism by which these devices predispose to clot, and provides a potential blueprint for both the design of newer devices and a reduction in complicated blood-thinning therapies for patients who receive these devices.”
“Dr. Bluestein’s research also lays the foundation for research that may be translated in vivo to help us predict, based on patient-pump specific platelet activation, which of our VAD patients may be at greatest risk for pump thrombosis,” said Allison J. McLarty, MD, Associate Professor of Surgery, Division of Cardiothoracic Surgery, and Co-Director of the VAD Program. Dr. McLarty is collaborating with Dr. Bluestein’s research team to advance clinical applications of the DTE methodology.
The research is partially supported by grants from the National Institute of Biomedical Imaging and Bioengineering and the National Institutes of Health.