Left heart assistance with the spindle pump.

The spindle pump--a new attempt at assisted circulation--was developed to prevent the main problems of nonpulsatile blood pumps, i.e. traumatic hemolysis, thrombus formation and sealing. It was essential to achieve adequate output with the lowest possible speed in order to minimize traumatic hemolysis. The result was a spindle pump with three windings in a U-shaped housing driven by an electric motor. Many tests were necessary to establish a prototype. The spindle was completely redesigned several times to reach an acceptable volume output and corresponding pressure output. In animal experiments this final prototype working as a LVAD, with a speed of 5400 RPM circulates 4 liters/min against BP of 110 mmHg. The hemolysis rate has been low in acute and survival experiments (27 hours up to now), and is between 25 and 30 mg/100 ml of free hemoglobin, thus within the normal range.