Preliminary in vivo study of an intra-aortic impeller pump driven by an extracorporeal whirling magnet

To achieve the aim of long-term heart-assist with a simple implantable device, we have been trying to develop a minimal intra-aortic impeller blood pump driven by an extracorporeal magnetic device. The purpose of the current study was to evaluate its feasibility by acute in vivo animal tests. The minimal intra-aortic pump was a cage-supported rotor-impeller, 17 mm in diameter with a total length of 30 mm. The driving magnet, mounted extracorporeally, was 55 mm in diameter and 50 mm in length. Seventeen dogs weighing from 28-34 kg were used in the study. After thoracic incision, heparin (50 U/kg) was infused. The impeller pump was inserted into the aortic chamber via a prosthetic vessel and fastened. Thin tubes were inserted into the left ventricular apex and the femoral artery to monitor the left ventricular (LV) and the aortic pressure. After closing the thoracic cavity, the extracorporeal whirling magnet, turned by an electric motor, was placed tightly against the thoracic wall parallel to the intra-aortic pump. The experiments, each lasting for about 40 min, were successful in 7 animals; the other 10 animals died of bleeding during pump implantation and were excluded from the experiment. The peak systolic pressure of the left ventricle could be considerably decreased by the pump and was reduced to as low as 28 mm Hg at a rotational speed of 9,000 rpm, showing that the simple intra-aortic impeller was effective in unloading the natural heart. The novel left ventricular assist device (LVAD) concept of an intra-aortic impeller pump, driven by an extracorporeal magnetic device, is feasible.