In Vitro Analysis of Hemodynamics in the Ascending Thoracic Aorta: Sensitivity to the Experimental Setup

We perform a stochastic sensitivity analysis of the experimental setup of a mock circulatory loop for in vitro hemodynamics analysis in the ascending thoracic aorta at a patient-specific level. The novelty of the work is that, for the first time, we provide a systematic sensitivity analysis of the effect of the inflow conditions, viz. the stroke volume, the cardiac cycle period, and the spatial distribution of the velocity in in-vitro experiments in a circulatory mock loop. We considered three different patient-specific geometries of the ascending thoracic aorta, viz. a healthy geometry, an aortic aneurysm, and a coarctation of the aorta. Three-dimensional-printed phantoms are inserted in a mock circulatory loop, and velocity and pressure measurements are carried out for the different setup conditions. The stochastic approach, performed using the generalized polynomial chaos, allows us to obtain continuous and accurate response surfaces in the parameter space, limiting the number of experiments. The main contributions of this work are that (i) the flow rate and pressure waveforms are mostly affected by the cardiac cycle period and the stroke volume, (ii) the impact of the spatial distribution of the inlet velocity profile is negligible, and (iii), from a practical viewpoint, this analysis confirms that in experiments it is also important to replicate the patient-specific inflow waveform, while the length of the pipe connecting the pump and the phantom of the aorta can be varied to comply with particular requirements as, for instance, those implied by the use of MRI in experiments.