Circulatory assistance in small infants and neonates with a hydraulically driven system: a viable option?

We have developed a new drive system for a cardiac assist system for use with newborns and infants. This study reports results of animal experiments in which this system was tested using a commercially available 25-ml ventricle. A major property of the device is its hydraulic mode, which allows not only for the conventional full-empty mode (chamber completely filled in diastole) but also for the filled-empty mode, in which the chamber is completely emptied in systole but only partially filled in systole; this mode gives full flexibility to adjust the pump frequency for any given pump flow rate. The assist device was applied in eight pigs (weight 9-14 kg) for left ventricular assistance during normal and impaired cardiac function (pacing-induced cardiac shock, mean arterial blood pressure less than 40 mmHg). Both, full-empty and filled-empty mode during normal cardiac function led to significantly decreased pulmonary capillary wedge pressure, suggesting load reduction of the right ventricle. In impaired cardiac function, circulatory assistance increased the diminished cardiac output and systolic arterial blood pressure, although only the latter was statistically significant. Neither arterial lactate concentration nor oxygen uptake was reduced during circulatory assistance for normal and impaired cardiac function. These results suggest that the cardiac ventricular assist device can be used as an effective circulatory assist device and that the function of the newly introduced filled-empty mode, which allows for a high degree of functional flexibility, is not inferior to that of the classical, but less flexible, full-empty mode.