Indirect Bronchial Shunt Flow Measurements in AbioCor Implantable Replacement Heart Recipients

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Abstract
Bronchial shunt flows in the recipients of the electrohydraulic AbioCor implantable replacement heart have been measured indirectly. A built-in compliance chamber accommodates the differential flow output required of the two ventricles of the AbioCor. An occluder mechanism regulates the flow differential. For a thoracic unit, given a beat rate, an occluder setting, and the pressure differentials across the replacement heart ventricles, the atrial pressure difference depends only on the level of shunt flow present in the vasculature. For a replacement heart recipient, the bronchial shunt is the dominant shunt flow. For patients implanted with the AbioCor, the beat rates and the occluder settings are known and the pressure differentials across the ventricles are estimated. Atrial pressures were measured using catheters. The bronchial shunt flow was deduced from in vitro characterization data based on these parameters. Available data from five patients in the ongoing clinical trial of AbioCor showed 0–1.4 L/minute bronchial shunt flows. Maximum variation for any individual patient was 1.1 L/minute.