The HeartMate III: Design and in vivo studies of a Maglev centrifugal leftventricular assist device

A compact implantable centrifugal left ventricular assist device (LVAD) (He artMate III) featuring a magnetically levitated impeller is under developme nt. The goal of our ongoing work is to demonstrate feasibility, low hemolys is, and low thrombogenicity of the titanium pump in chronic bovine in vivo studies. The LVAD is based on so-called bearingless motor technology and co mbines pump rotor, drive, and magnetic bearing functions in a single unit. The impeller is rotated (theta (7)) and levitated with both active (X, Y) a nd passive (Z, theta (x), theta (y)) suspension. Six prototype systems have been built featuring an implantable titanium pump (69 mm diameter, 30 mm h eight) with textured blood contacting surfaces and extracorporeal electroni cs. The pumps were implanted in 9 calves (less than or equal to 100 kg at i mplant) that were anticoagulated with Coumadin (2.5 less than or equal to I NR less than or equal to 4.0) throughout the studies. Six studies were elec tively terminated (at 27-61 days), 1 study was terminated after the develop ment of severe pneumonia and lung atelectasis (at 27 days) another study wa s terminated after cardiac arrest (at 2 days) while a final study is ongoin g (at approximate to 100 days). Mean pump flows ranged from 2 to 7 L/min, e xcept for brief periods of exercise at 6 to 9 L/min. Plasma free hemoglobin ranged from 4 to 10 mg/dl. All measured biochemical indicators of end orga n function remained within normal range. The pumps have met performance req uirements in all 9 implants with acceptable hemolysis and no mechanical fai lures.