Patent ID: 8506470

Claim:
A heart ventricle assist system comprising: a blood pump having a magnetically rotatable impeller; a plurality of stator drive coils magnetically coupled to said impeller to enable it to rotate; a motor control circuit adapted to provide motor control signals to said drive coils thereby magnetically to rotate said impeller within said blood pump to establish a predetermined steady state blood flow rate, said motor control circuit continuously monitoring the rotational speed of said impeller; and a controller adapted to interrupt said motor control signals at predetermined intervals, each interval consisting of a predetermined period of time, thereby to permit a decay in rotational speed of said impeller during each predetermined period of time, said controller adapted to measure values and time between minimum and maximum back EMF signals generated within said stator coils during each predetermined period and to determine therefrom a transient viscosity value of blood in said blood pump, said motor control circuit establishing a rotational speed of said impeller sufficient to create a steady state blood flow rate which is a function of said transient viscosity value between each of said predetermined intervals.