Hemodynamic Effects of Various Support Modes of Continuous Flow LVADs on the Cardiovascular System: A Numerical Study

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.

Material and 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.