In Vivo Study of an LVAD Prototype with a Hybrid Magnetic Bearing

J. P. Willis, D. H. Locke, P. Hryniewicz, S. Jahanmir, and H. Heshmat, “In Vivo Study of an LVAD Prototype with a Hybrid Magnetic Bearing,” ASAIO Journal, 49 (2003) 176. 

A second-generation prototype of a high efficiency, non-pulsatile rotary blood pump was developed for use as a left ventricular assist device (LVAD). The LVAD pump uses a hybrid passive/active magnetic bearing support system which exhibits low power losses, low vibration, and high reliability under transient conditions and varying pump orientations. Unique features of the design are the simple and direct flow path for both main and washing blood flows, the non-contact pump rotor, i.e., no rubbing surfaces, and relatively large clearances (≥ 5 mm) between the pump rotor and housing.

The prototype was constructed from medical grade polycarbonate. To reduce the possibility of thrombosis, the internally exposed surface area was coated with a biocompatible polymer. The purpose of this study was to determine the in vivo form, fit and function of the pump in a calf model. Hemolysis testing, with bovine blood, was performed at the Hershey Medical Center of Pennsylvania State University. The test results showed a low normalized index of hemolysis of 0.05 g/100 L. Encouraged by these results, an acute animal test was successfully completed at the Hershey Medical Center. During the test, the pump was implanted in a calf and operated in parallel with the calf’s heart. Following the acute test a chronic implant study was completed. The results of these in vivo tests are discussed.

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