Getting Past the Spin: The CorWave LVAD, a Membrane Wave Pump Providing Physiologic Pulsatility without High Shear

Abstract

Purpose A new LVAD is under development which employs a completely novel pumping technology. Magnetically driven oscillation of a polymer membrane creates a wave motion, gently pushing the blood through the pump. By changing the oscillation frequency and magnitude, pressure generation and blood flow rates can be dynamically adjusted over timescales as short as 30 msec. This approach offers a less damaging method for efficiently pumping blood while generating physiologic pulsatility. We evaluated pump actuation parameters and control algorithms in mock circulation loops and an acute animal study to evaluate and optimize pulse generation. Methods The LVAD was evaluated on a physiologic mock-loop to determine the optimal performance parameters. Pulsatility is created by switching rapidly between levels of pump output. A period of high output was generated following detection of systole to augment native cardiac output. Pump flow was reduced during diastole to avoid suck-down of the ventricle and limit back flow. The initial target was pump generated aortic dP/dt of >400 mmHg/sec under heart failure conditions with pump flow of 3-6 LPM. In parallel, hemolysis was measured using porcine blood. The pulsatility algorithm was evaluated with the pump implanted in an ovine model to validate the systole detection method. Results Evaluation on the mock circulatory loop achieved a high degree of pulsatility, defined as delta AoP=40mmHg, dP/dt=410mmHg/s, AoF=4.7 lpm, MAP=83mmHg vs. heart failure model of delta AoP=28mmHg, dP/dt=430mmHg/s, AoF=3.7lpm, MAP= 67mmHg. Generation of free hemoglobin at both high and low operating points are in a clinically acceptable range and well controlled transition between the two points does not significantly increase hemolysis. The acute animal study, the pulsatility algorithm correctly detected systole in >90% of beats. Conclusion Bench testing indicated that the pump provided augmented pulsatility to the failing heart, while achieving targeted levels of aortic flow and pressure without increased hemoglobin release. Augmented pulsatility offers a new mechanism to reduce bleeding and renal complications of VAD therapy with the intriguing possibly to increase cardiac recovery. Studies are underway to further evaluate the pulsatile operating mode algorithms and related hemoglobin release in an ovine heart failure model.