In Vitro Test Bench Reproducing Coronary Blood Flow Signals

It is a known fact that blood flow pattern and more specifically the pulsatile time variation of shear stress on the vascular wall play a key role in atherogenesis. The paper presents the conception, the building and the control of a new in vitro test bench that mimics the pulsatile flows behavior based on in vivo measurements.

An in vitro cardiovascular simulator is alimented with in vivo constraints upstream and provided with further post-processing analysis downstream in order to mimic the pulsatile in vivo blood flow quantities. This real-time controlled system is designed to perform real pulsatile in vivo blood flow signals to study endothelial cells’ behavior under near physiological environment. The system enables to mimic any resulting blood flow rate patterns between 40 and 700 ml/min. In order to feed the system with reliable periodic flow quantities in vivo measurements were performed. Data from five patients (1 female, 4 males; ages 44-63) were filtered and post-processed using the Newtonian Womersley’s solution. These resulting flow signals were compared with 2D axisymmetric, numerical simulation using a Carreau non-Newtonian model to validate the approximation of a Newtonian behavior.

Comparison between flow rates calculated by the Womersley’s solution in in vivo blood vessels and in the in vitro test bench. The Fourier spectral analysis was calculated in order to assess the differences in reproduced frequencies between Womersley’s solution (*black line*) and ones obtained in vitro (*grey line*) (*left-hand panel*).

The pulse duplicator reproduces the measured flow rate time evolution
and the complexity of in vivo hemodynamic signals with a relative error below 5%. Wall shear stress were calculated in the anurysm sulicone model and the picture represents the comparison between wall shear stress and wall shear stress time derivative calculated by the Womersley’s solution in in vivo blood vessels and in the in vitro test bench. Hemodynamic properties, such as the wall shear stress (left panel) and wall shear stress time derivative (right panel) were calculated from Womersley simulations of in vivo data (solid black lines) and from reproduction by our in vitro test bench (solid grey lines) and plotted against time. Rows from top to bottom refer to patients from 1 to 5. All graphs are drawn for one period cycle.