FLOW CHARACTERISTICS OF THE HEMOPUMP - AN EXPERIMENTAL IN-VITRO STUDY

Background. The Hemopump (DLP/Medtronic) has been in clinical we for a bout 7 years. There is still no adequate way of determining actual out put from the three available pump systems in the clinical situation. I f the pump is completely stopped during weaning from the device, there is a possibility of back-leakage through the pump, endangering the pa tient from regurgitation into the left ventricle. It can also make it more difficult to judge the recovery of heart function because of a vo lume load of the left ventricle. The aim of this study was to evaluate in a standardized, experimental in vitro model the output from three different-sized Hemopump catheters at various pressure levels and to q uantify the backflow through the pumps. Methods. The Hemopump models w ere tested in an in vitro study regarding total outflow at various spe eds at three pressure levels. The back-how through the pumps was also measured with the pumps at a complete stop. Results. The outflow from the Hemopumps ranged from 0.4 to 4.5 L/min, depending on which pump an d speed were used. Variations in total output, depending on speed and various pressure settings, could be up to 0.4 L/min. Back-flow through the pump into the left ventricle may he as great as 1.6 L/min. Conclu sions. The flow outputs from the different Hemopump models were reprod ucible over time and were closely related to the resistance of the mod el. The Hemopump, if not running can induce substantial regurgitation through the pump into the left ventricle. (C) 1997 by The Society of T horacic Surgeons