Cardiac intervention, myocardial infarction, or postoperative heart failure
will sometimes create a need for circulatory support. For this purpose, a
new, minimally invasive intraaortic 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 hydrau
lic properties of the pump in a bench test. The axial flow pump is a cathet
er system with a distal motor driven foldable propeller (0 -15,000 revoluti
ons per minute). To protect the aortic wall, filaments forming a cage surro
und 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 cha
racteristics. Propellers and tubes with different diameters were studied, a
nd pressure and flow characteristics were measured. The mathematical relati
onships between pressure and rotational speed, pressure, and diameter of pr
opeller and tube were determined. There was a positive relationship between
the revolutions per minute and the generated pressure, a positive relation
ship between the diameter of the propeller and pressure, and a negative rel
ationship between the diameter of the tube and the generated pressure. With
in the physiologic range of cardiac output, there was a small drop in press
ure with increasing flow in the tubes with a small diameter. With an increa
sing diameter of the tube, a smaller pressure drop was seen with increasing
flow. The present cardiac support system has hydraulic properties, which m
ay be of clinical relevance for patients with left ventricular heart failur
e.