title: Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller.
abstract: Unlike the earlier reciprocating volume displacement-type pumps, rotary blood pumps (RBPs) typically operate at a constant rotational speed and produce continuous outflow. When RBP technology is used in constructing a total artificial heart (TAH), the pressure waveform that the TAH produces is flat, without the rise and fall associated with a normal arterial pulse. Several studies have suggested that pulseless circulation may impair microcirculatory perfusion and the autoregulatory response and may contribute to adverse events such as gastrointestinal bleeding, arteriovenous malformations, and pump thrombosis. It may therefore be beneficial to attempt to reproduce pulsatile output, similar to that generated by the native heart, by rapidly modulating the speed of an RBP impeller. The choice of an appropriate speed profile and control strategy to generate physiologic waveforms while minimizing power consumption and blood trauma becomes a challenge. In this study, pump operation modes with six different speed profiles using the BiVACOR TAH were evaluated in vitro. These modes were compared with respect to: hemodynamic pulsatility, which was quantified as surplus hemodynamic energy (SHE); maximum rate of change of pressure (dP/dt); pulse power index; and motor power consumption as a function of pulse pressure. The results showed that the evaluated variables underwent different trends in response to changes in the speed profile shape. The findings indicated a possible trade-off between SHE levels and flow rate pulsatility related to the relative systolic duration in the speed profile. Furthermore, none of the evaluated measures was sufficient to fully characterize hemodynamic pulsatility.
authors.affiliation: School of Engineering, Griffith University, Southport, Queensland, Australia. matthias.kleinheyer@griffithuni.edu.au.|Department of Engineering, BiVACOR Inc., Houston, TX, USA. matthias.kleinheyer@griffithuni.edu.au.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kleinheyer
authors.affiliation: Department of Engineering, BiVACOR Inc., Houston, TX, USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Timms
authors.affiliation: School of Engineering, Griffith University, Southport, Queensland, Australia.
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Tansley
authors.affiliation: Department of Engineering, BiVACOR Inc., Houston, TX, USA.|School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Frank
authors.initials: F
authors.lastname: Nestler
authors.affiliation: Department of Engineering, BiVACOR Inc., Houston, TX, USA.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Greatrex
authors.affiliation: Department of Engineering, BiVACOR Inc., Houston, TX, USA.|Department of Cardiovascular Surgery, Texas Heart Institute, Houston, TX, USA.
authors.forename: O Howard
authors.initials: OH
authors.lastname: Frazier
authors.affiliation: Department of Engineering, BiVACOR Inc., Houston, TX, USA.|Department of Cardiovascular Surgery, Texas Heart Institute, Houston, TX, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Cohn
mesh_terms: D001794:Blood Pressure; D004867:Equipment Design; D006354:Heart, Artificial / Q000191:economics; D006439:Hemodynamics; D006801:Humans; D008833:Microcirculation; D008955:Models, Cardiovascular; D011312:Pressure; D011673:Pulsatile Flow
keywords: Rapid speed modulation-Total artificial heart-Rotary blood pump-Speed profile-Efficiency-Mechanical circulatory support