Clinical studies have reported the balancing of pump outputs to be a serious control issue for rotary biventricular support (BiVS) systems. Poor reliability of long-term, blood immersed pressure sensors encouraged the development of a new control strategy to improve their viability. A rotary BiVS device was designed and constructed with a mechanical passive controller to autoregulate pump outputs to emulate the native baroreceptor response. In vitro testing in a dual circuit, hydraulic mock circulation loop showed that the prototype was able to maintain arterial pressures when subjected to sudden induced hemodynamic destabilization. However, inlet suction was observed when sudden simulated hypertension briefly reduced venous return to the cannulated ventricle. The results have encouraged further development of the device as a means to create an inherently stable, fully passive biventricular support device.