Initial tests with a new cardiac assist device

Before, during, and after cardiac intervention, there is occasionally a nee d for circulatory support because of hemodynamic deterioration. For this pu rpose, a new minimally invasive cardiac assist device has been developed, a nd an early prototype has been studied in a bench test and in three pigs. T he pump is a catheter system with a distal motor driven propeller (0-15,000 rpm) surrounded by a cage. The catheter was first tested in a tube in a wa ter bath, where efficiency with respect to pressure generation and flow pro perties was measured. In the pig experiments, the pump was placed in the de scending part of the aorta via a graft, and hemodynamic effects were record ed with three different propellers. The bench tests showed a velocity depen dent pressure generation in the tube to the second power of the rpm, and 30 cm of water (> 22 mm Hg) could easily be achieved with all propellers. A p ressure dependent flow in the tube was observed, with maximum flows of 20 L at 12,000 rpm and 27 L at 15,000 rpm. In the animal experiments, there was a velocity dependent mean pressure difference across the propeller, with u p to 48 mm of mercury for the biggest propeller. An increase in cardiac out put in all of the pigs was observed as well as a drop in pressure in the pr oximal part of the aorta. This study demonstrates the efficiency of this ne w device in vitro and in vivo. Hemodynamic changes are pronounced and are r elated to the speed and size of the propeller.