Downsizing of a Pulsatile Total Artificial Heart—The Effect on Hemolysis

Abstract

A downsized version of the ReinHeart total artificial heart (TAH) was developed. Hemocompatibility needs to be revised since the operating point of the downsized TAH has changed to a higher pump frequency to accomplish the same cardiac output. A mock circulation loop was designed, containing a left side for hemocompatibility testing and a right side to mimic realistic work conditions. A protocol for hemolysis testing was established using pooled porcine blood with an operation point of 5 L/min, a mean outlet pressure of 100 mm Hg and a mean inlet pressure of 12 mm Hg. Six trials were performed testing two downsized TAH (one with a compliance chamber [CC] connected, necessary for a pneumatic decoupling of both membranes and one open to atmosphere) and a BPX-80 as reference pump. The average modified index of hemolysis and normalized index of hemolysis (NIH in mg/100L) from six individual trials of the reference pump were 0.34 (0.07) and 3.21 (0.61) and of the TAH open to atmosphere 4.18 (1.19) and 38.85 (10.59), respectively. In between TAH with and without CC, there was no significant difference. A NIH ratio of TAH and reference pump was calculated to minimize variation of the different blood batches used in individual trials. Due to the downsizing, the ReinHeart's hemolysis level increased by around 22% compared with the original size version. Comparing the results to clinically approved left ventricular assist devices, the level of hemolysis can still be considered acceptable.

Fluid–structure interaction modelling of a positive-displacement Total Artificial Heart

“…This suggests that a small decrease in time-averaged can be achieved by increasing the stroke length and decreasing the heart rate. This points towards the same conclusion drawn by both Syncardia 32 and ReinHeart 55 : an increase in heart rate due to downsizing the pump resulted in higher levels of shear stress and haemolysis. The method of reducing shear stresses observed in this study is at odds with the outcome found for increasing washout rate, suggesting that a trade-off would have to be made between shear stress levels and washout performance.…”

In vitro hemolytic performance of the Realheart®V11C TAHprototype with porcine blood

“…ac.biomed successfully produced the Aachen test rig for pulsatile devices 20,21 demonstrated by reproducible results for the control pump BPX‐80. It achieved a mgNIH value of 5.42 mg/100 L, comparable to previous BPX‐80 hemolysis studies with a range of 2.6–6.6 mg/100 L for porcine 20,21,23–27 and 2.4–7.1 mg/100 L for bovine blood 18 …”

“…Pooling blood, although acceptable, is not ideal, because it induces hemolysis, changes erythrocyte resistance against trauma, 19 and limits the study of additional parameters. The Aachen rig was developed to test the pulsatile Reinheart TAH and uses compliance chambers with inflatable silicon bellows to maintain low blood volume 20,21 . The aim herein was to evaluate the in vitro hemolysis of the Realheart® TAH V11C left pump prototype (V11C) with porcine blood in the Aachen rig at one operating point, to enable performance comparison with literature.…”

“…The Aachen rig was developed to test the pulsatile Reinheart TAH and uses compliance chambers with inflatable silicon bellows to maintain low blood volume. 20,21 The aim herein was to evaluate the in vitro hemolysis of the Realheart® TAH V11C left pump prototype (V11C) with porcine blood in the Aachen rig at one operating point, to enable performance comparison with literature. The independent contractor ac.biomed constructed the Aachen test rig to acquire the capability to offer it to other device developers.…”

Total artificial heart system

“…Upon cessation of bleeding, anticoagulation therapy with a heparin infusion (goal activated partial thromboplastin time of 40 to 60 s) and antiplatelet therapy (aspirin 81 to 324 mg) must be initiated, with eventual bridging to warfarin (target international normalized ratio of 2.5 to 3.0) 11. Postoperative anemia is common in TAH patients and is most commonly due to bleeding and hemolysis caused by mechanical valve sheering 7,10. However, because patients receive TAH support as BTT, transfusion of blood products should be limited to avoid foreign antigen exposure.…”