title: Hemodynamic effects of various support modes of continuous flow LVADs on the cardiovascular system: a numerical study.
abstract: BACKGROUND
  The aim of this study was to determine the hemodynamic effects of various support modes of continuous flow left ventricular assist devices (CF-LVADs) on the cardiovascular system using a numerical cardiovascular system model.
  
  
  METHODS
  Three support modes were selected for controlling the CF-LVAD: constant flow mode, constant speed mode, and constant pressure head mode of CF-LVAD. The CF-LVAD is established between the left ventricular apex and the ascending aorta, and was incorporated into the numerical model. Various parameters were evaluated, including the blood assist index (BAI), the left ventricular external work (LVEW), the energy of blood flow (EBF), pulsatility index (PI), and surplus hemodynamic energy (SHE).
  
  
  RESULTS
  The results show that the constant flow mode, when compared to the constant speed mode and the constant pressure head mode, increases LVEW by 31% and 14%, and EBF by 21% and 15%, respectively, indicating that this mode achieved the best ventricular unloading among the 3 support modes. As BAI is increased, PI and SHE are gradually decreased, whereas PI of the constant pressure head reaches the maximum value.
  
  
  CONCLUSIONS
  The study demonstrates that the continuous flow control mode of the CF-LVAD may achieve the highest ventricular unloading. In contrast, the constant rotational speed mode permits the optimal blood perfusion. Finally, the constant pressure head strategy, permitting optimal pulsatility, should optimize the vascular function.
authors.affiliation: Department of Cardiac Surgery, Peking University Third Hospital, Beijing, China (mainland).
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Song
authors.affiliation: School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland).
authors.forename: Kaiyun
authors.initials: K
authors.lastname: Gu
authors.affiliation: School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland).
authors.forename: Bin
authors.initials: B
authors.lastname: Gao
authors.affiliation: Department of Cardiac Surgery, Peking University Third Hospital, Beijing, China (mainland).
authors.forename: Feng
authors.initials: F
authors.lastname: Wan
authors.affiliation: School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland).
authors.forename: Yu
authors.initials: Y
authors.lastname: Chang
authors.affiliation: School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland).
authors.forename: Yi
authors.initials: Y
authors.lastname: Zeng
mesh_terms: D001021:Aortic Valve / Q000503:physiopathology; D003198:Computer Simulation; D003326:Coronary Circulation / Q000502:physiology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006353:Heart-Assist Devices; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular; D009716:Numerical Analysis, Computer-Assisted; D011673:Pulsatile Flow