The use of left ventricular assist devices (LVADs) in patients with advanced heart failure
improves outcomes. The adaption of LVAD speed to individual needs is facilitated by the
monitoring of pressures volumes and flows in the circulation. Particularly the left
ventricular volume (LVV) is a robust input variable for physiological LVAD control and its
monitoring reduces rehospitalizations. Bioimpedance measurements have been identified as a tool
for assessing LVV. However established techniques require elaborate in-vivo calibration or
overestimate absolute LVV.This work provides methods and models for improved hemodynamic
monitoring from bioimpedance measurements. Complex electric field distributions of bi- and
tetrapolar measurement configurations within the aorta and left ventricle are translated into
new techniques that estimate cardiac output (CO) and LVV. The fusion of bioimpedance and
ultrasound sensors is realized to assess LVV requiring in-vitro calibration only. In-silico and
in-vitro models are developed and applied to validate the developed methods. In-vitro phantoms
mimic the dielectric and geometric properties of the left ventricle mitigating costly animal
testing. The optimal placement of electrodes to detect the center radius of the left ventricle
and the flow through the aorta is determined in-silico for tetra- and bipolar configurations. A
conclusive in-vivo experiment confirms the results obtained by the in-vitro and in-silico
models demonstrating that the proposed methods for the estimation of LVV outperform state of
the art.The reliable estimation of LVV and CO has the potential to improve treatment in
advanced heart failure and reducing mortality. The established methods lay the foundation for
physiological control in LVAD therapy.
