Hydrodynamic Properties of a New Percutaneous Intra-aortic Axial Flow Pump

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Abstract
Cardiac intervention, myocardial infarction, or postoperative heart failure will sometimes create a need for circulatory support. For this purpose, a new, minimally invasive intra-aortic cardiac support system with a foldable propeller has been developed. In animals, the pump has been shown to have a positive hemodynamic influence, and the present study evaluates the hydraulic properties of the pump in a bench test. The axial flow pump is a catheter system with a distal motor driven foldable propeller (0-15,000 revolutions per minute). To protect the aortic wall, filaments forming a cage surround the propeller. In the present study, tests were done with two different pumps, one with and one without the cage. Two different models were used, one for testing pressure generation and one for obtaining flow-pressure characteristics. Propellers and tubes with different diameters were studied, and pressure and flow characteristics were measured. The mathematical relationships between pressure and rotational speed, pressure, and diameter of propeller and tube were determined. There was a positive relationship between the revolutions per minute and the generated pressure, a positive relationship between the diameter of the propeller and pressure, and a negative relationship between the diameter of the tube and the generated pressure. Within the physiologic range of cardiac output, there was a small drop in pressure with increasing flow in the tubes with a small diameter. With an increasing diameter of the tube, a smaller pressure drop was seen with increasing flow. The present cardiac support system has hydraulic properties, which may be of clinical relevance for patients with left ventricular heart failure.