Abstracts: ASAIO Cardiac Abstracts
IN VITRO ASSESSMENT OF A ROTARY LVAD-INDUCED ARTIFICIAL PULSE
We previously established that an artificial pulse could be produced in vivo by modulating the magnetically levitated rotor speed in the Thoratec HeartMate® III. Here, we reproduced the waveform under laboratory conditions and optimized system parameters for desired pulse characteristics.
A mock circulatory loop simulated the pressures previously observed in an ovine thoracic aorta supported by a HMIII alternating between 1500 and 5500 rpm. Pulse pressure was initially adjusted to 60 mmHg and dp/dt was 250 mmHg/s. The effects of speed change rate, duty cycle, and beat rate on dp/dt, energy equivalent pressure (EEP), and efficiency were investigated.
Increasing speed change rate increased dp/dt to 1200 mmHg/s and EEP over MAP by 3% without affecting stability. Power consumption increased by 8% to 12.7 W, about double that required for non-pulsatile operation. Increasing duty cycle from 50% to 75% to 85% increased the flow by 22% and 31%, but slightly decreased efficiency. Decreasing the beat rate from 60 to 50 to 40 bpm had little effect on flow but increased the hydraulic efficiency by 2% and 3%.
The HMIII can simulate physiologic pulse and dp/dt. Flow and efficiency penalties intrinsic to pulsatile operation are palliated by increasing duty cycle and decreasing beat rate.Copyright © 2005 by the American Society for Artificial Internal Organs