Prolonged biventricular assist device support as a bridge to heart transplantation

Thromboresistance comparison of the HeartMate II ventricular assist device with the device thrombogenicity emulation- optimized HeartAssist 5 VAD

Approximately 7.5 × 106 patients in the US currently suffer from end-stage heart failure. The FDA has recently approved the designations of the Thoratec HeartMate II ventricular assist device (VAD) for both bridge-to-transplant and destination therapy (DT) due to its mechanical durability and improved hemodynamics. However, incidence of pump thrombosis and thromboembolic events remains high, and the life-long complex pharmacological regimens are mandatory in its VAD recipients. We have previously successfully applied our device thrombogenicity emulation (DTE) methodology for optimizing device thromboresistance to the Micromed Debakey VAD, and demonstrated that optimizing device features implicated in exposing blood to elevated shear stresses and exposure times significantly reduces shear-induced platelet activation and significantly improves the device thromboresistance. In the present study, we compared the thrombogenicity of the FDA-approved HeartMate II VAD with the DTE-optimized Debakey VAD (now labeled HeartAssist 5). With quantitative probability density functions of the stress accumulation along large number of platelet trajectories within each device which were extracted from numerical flow simulations in each device, and through measurements of platelet activation rates in recirculation flow loops, we specifically show that: (a) Platelets flowing through the HeartAssist 5 are exposed to significantly lower stress accumulation that lead to platelet activation than the HeartMate II, especially at the impeller-shroud gap regions (b) Thrombus formation patterns observed in the HeartMate II are absent in the HeartAssist 5 (c) 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 thrombogenic performance comparative study of the two VADs, one optimized with the DTE methodology and one FDA-approved, demonstrates the efficacy of the DTE methodology for drastically reducing the device thrombogenic potential, validating the need for a robust in silico/in vitro optimization methodology for improving cardiovascular devices thromboresistance.

Seventeen-month-long paracorporeal biventricular mechanical support as a bridge to transplantation for severe dilated cardiomyopathy

The long-term management of paracorporeal biventricular assist devices (BiVAD) is difficult because of significant risks of bleeding, thrombosis, and infection. Here we report the case of a 41-year-old woman with severe dilated cardiomyopathy who developed serious cerebral bleeding after receiving a paracorporeal BiVAD but recovered well after treatment. She eventually underwent cardiac transplantation 17 months after implantation of the paracorporeal BiVAD.

Spontaneous increase in EVAHEART® pump flow at a constant pump speed during exercise examination

PURPOSE

Ventricular assist devices have been used for the treatment of severe heart failure. Recently, many types of blood pumps have been developed to reduce major adverse events. EVAHEART® (Sun Medical Technology Research Corporation, Nagano, Japan) is an implantable centrifugal blood pump. In laboratory animal studies, the pump flow of EVAHEART® increases spontaneously during exercise with no changes in pump control parameters. However, this has not been confirmed clinically. The aim of this study was to analyze EVAHEART® performance during exercise.

PATIENTS AND METHODS

Four male patients were implanted with an EVAHEART®. We evaluated the performance of the EVAHEART® during exercise. Fixed pump speeds were maintained during each test. Measurements during exercise were peak load, peak oxygen consumption (peak VO(2)), pre exercise pump flow, and peak velocity.

RESULTS

Pump flow significantly increased from 4.1 ± 0.5 liters per minute (L/min) to 7.2 ± 1.8 L/min during exercise. VO(2) increased from 4.0 ± 0.7 milliliters per kilogram per minute (ml/kg/min) to 14.7 ± 3.3 ml/kg/min.

CONCLUSION

These results indicate that EVAHEART® may support severe heart failure patients not only under static but also under dynamic conditions. Pump flow spontaneously increased during exercise at a constant pump speed.