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.
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The objective of this study is to identify the preload and afterload sensitivity of the ReinHeart TAH 2.0. For adequate left-right flow balance, the concept of a reduced right stroke volume (by about 10%) and active adaption of the right diastole duration are evaluated concerning the controllability of the flow balance. This study used an active mock circulation loop to test a wide range of preload and afterload conditions.Preload sensitivity was tested at atrial pressures (APs) between 4 and 20 mm Hg. Left afterload was varied in a range of 60-140 mm Hg mean aortic pressure (MAP), right afterload was simulated between 15 and 40 mm Hg. Four scenarios were developed to verify that the flow difference fully covers the defined target range of 0-1.5 L/min. Although a positive correlation between inlet pressure and flow is identified for the right pump chamber, the left pump chamber already fills completely at an inlet pressure of 8-10 mm Hg. With increasing afterload, both the left and right flow decrease.A positive flow balance (left flow exceeds right flow) is achieved over the full range of tested afterloads. At high APs, the flow difference is limited to a maximum of 0.7 L/min. The controllability of flow balance was successfully evaluated in four scenarios, revealing that a positive flow difference can be achieved over the full range of MAPs. Under physiological test conditions, the linear relationship between flow and heart rate was confirmed, ensuring good controllability of the TAH.
An in-vitro study was conducted to investigate the general feasibility of using only one pumping chamber of the SynCardia total artificial heart (TAH) as a replacement of the single ventricle palliated by Fontan circulation. A mock circulation loop was used to mimic a Fontan circulation. The combination of both ventricle sizes (50 and 70 cc) and driver (Freedom Driver and Companion C2 Driver) was investigated. Two clinical relevant scenarios (early Fontan; late Fontan) as derived from literature data were set up in the mock loop. The impact of increased transpulmonary pressure gradient, low atrial pressure, and raised central venous pressure on cardiac output was studied. From a hemodynamic point, the single-chambered TAH performed sufficiently in the setting of the Fontan circulation. Increased transpulmonary pressure gradient, from ideal to pulmonary hypertension, decreased the blood flow in combinations by almost 2 L/min. In the early Fontan scenario, a cardiac output of 3–3.5 L/min was achieved using the 50 cc ventricle, driven by the Companion C2 Driver. Even under pulmonary hypertension, cardiac outputs greater than 4 L/min could be obtained with the 70 cc pump chamber in the late Fontan scenario. In the clinically relevant Fontan scenarios, implementation of the single chambered TAH performed successfully from a hemodynamic point of view. The replacement of the failing univentricular heart by a single chamber of the SynCardia TAH may provide an alternative to a complex biventricular repair procedure or ventricular support in Fontan patients.
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