In-silico enhanced animal study of pulmonary artery pressure sensors: assessing hemodynamics using computational fluid dynamics

Abstract

To assess whether in-silico models can be used to predict the risk of thrombus formation in pulmonary artery pressure sensors (PAPS), a chronic animal study using pigs was conducted. Computed tomography (CT) data was acquired before and immediately after implantation, as well as one and three months after the implantation. Devices were implanted into 10 pigs, each one in the left and right pulmonary artery (PA), to reduce the required number of animal experiments. The implantation procedure aimed at facilitating optimal and non-optimal positioning of the devices to increase chances of thrombus formation. Eight devices were positioned non-optimally. Three devices were positioned in the main PA instead of the left and right PA. Pre-interventional PA geometries were reconstructed from the respective CT images, and the devices were virtually implanted at the exact sites and orientations indicated by the follow-up CT after one month. Transient intra-arterial hemodynamics were calculated using computational fluid dynamics. Volume flow rates were modelled specifically matching the animals body weights. Wall shear stresses (WSS) and oscillatory shear indices (OSI) before and after device implantation were compared. Simulations revealed no relevant changes in any investigated hemodynamic parameters due to device implantation. Even in cases, where devices were implanted in a non-optimal manner, no marked differences in hemodynamic parameters compared to devices implanted in an optimal position were found. Before implantation time and surface-averaged WSS was $2.35\pm 0.47$ Pa, whereas OSI was $0.08\pm 0.17$, respectively. Areas affected by low WSS magnitudes were $2.5\pm 2.7$ cm${}^2$, whereas the areas affected by high OSI were $18.1\pm 6.3$ cm${}^2$. After device implantation, WSS and OSI were $2.45\pm 0.49$ Pa and $0.08\pm 0.16$, respectively. Surface areas affected by low WSS and high OSI were $2.9\pm 2.7$ cm${}^2$, and $18.4\pm 6.1$ cm${}^2$, respectively. This in-silico study indicates that no clinically relevant differences in intra-arterial hemodynamics are occurring after device implantation, even at non-optimal positioning of the sensor. Simultaneously, no embolic events were observed, suggesting that the risk for thrombus formation after device implantation is low and independent of the sensor position.

Keywords: computational fluid dynamics; computed tomography; heart failure; oscillating shear index; porcine animal model; pressure sensor; pulmonary artery; wall shear stress.