Early in vivo evaluation of ventricular assistance with a miniature centrifugal blood pump (TinyPump) in rabbits.

We have developed an ultraminiature centrifugal pump, TinyPump, with a priming volume of 5 ml. The in vivo performance of TinyPump was compared with that of HPM-05 for left ventricular support. Each pump group included seven rabbits weighing 3.4-3.8 kg. One rabbit in the TinyPump group and two rabbits in the HPM-05 group died of unsuccessful cannulation. The remaining rabbits (six in the TinyPump group and five in the HPM-05 group) were instrumented and observed for 240 minutes. The pump flow was maintained at around 200 ml/min. The priming volumes of the entire circuits were 25 and 45 ml for TinyPump and HPM-05, respectively. TinyPump required a higher rotation speed (2214 +/- 47 vs. 1261 +/- 87 rpm, p < 0.05) because of its small priming volume but showed a similar plasma free hemoglobin level to HPM-05. The hematocrit values were kept higher in the TinyPump group during ventricular support (24.3 +/- 1.4% vs. 20.1 +/- 1.4% at 240 minutes, p < 0.05). The mean arterial pressure did not differ between the two groups. The biochemical parameters were also equivalent in the two groups. Overall, TinyPump exhibited a feasible in vivo performance. This ultraminiature device would offer promising outcomes for neonates and infants with intractable heart failure.