Development and current clinical application of ventricular assist devices in China
In order to avoid mechanical wear in artificial heart pumps for long-term application, the author developed 2 prototypes of permanent maglev left ventricular assist devices(LVAD): axially driven centrifugal pump, and radially driven centrifugal pump, in which a passive magnetic(PM) bearing in common use(Bearing A) and a novel PM bearing developed by the author(Bearing B) were used respectively. The permanent maglev impeller centrifugal pumps were tested in laboratory with normal saline. For the first pump, its motor magnets could be seen through a Plexiglas housing of the device. At the standstill, the rotor had only one contact point with the stator. As the rotor increased its rotating speed to over 4000rpm, the rotor moved axially off from the contact point about 0.5mm and disaffiliated from the stator, and became fully levitated. For the second pump, its rotor eccentric distance was measured by 4 Hall-sensors symmetrically fixed on the periphery of the stator. The experiment indicated that the eccentricity and vibration amplitudes would be under 0.07mm and 0.06mm respectively, smaller than the gap between the rotor and the stator (0.15mm), if the rotating speed increased to over 3250rpm. That means the rotor had no contact with the stator, namely, was suspended in the stator. The results demonstrate that passive magnetic bearings could achieve stable magnetic levitation in both of the centrifugal heart pumps, when rotating speed reaches high enough and thus obtains a so-called gyro-effect, namely, a rotating body with high enough speed could maintain its rotation stably.