An Experimental-Computational Study of Catheter Induced Alterations in Pulse Wave Velocity in Anesthetized Mice

Abstract

Computational methods for solving problems of fluid dynamics and fluid-solid-interactions have advanced to the point that they enable reliable estimates of many hemodynamic quantities, including those important for studying vascular mechanobiology or designing medical devices. In this paper, we use a customized version of the open source code SimVascular to develop a computational model of central artery hemodynamics in anesthetized mice that is informed with experimental data on regional geometries, blood flows and pressures, and biaxial wall properties. After validating a baseline model against available data, we then use the model to investigate the effects of commercially available catheters on the very parameters that they are designed to measure, namely, murine blood pressure and (pressure) pulse wave velocity (PWV). We found that a combination of two small profile catheters designed to measure pressure simultaneously in the ascending aorta and femoral artery increased the PWV due to an overall increase in pressure within the arterial system. Conversely, a larger profile dual-sensor pressure catheter inserted through a carotid artery into the descending thoracic aorta decreased the PWV due to an overall decrease in pressure. In both cases, similar reductions in cardiac output were observed due to increased peripheral vascular resistance. As might be expected, therefore, invasive transducers can alter the very quantities that are designed to measure, yet advanced computational models offer a unique method to evaluate or augment such measurements.

Figure 1

a) Corrosion cast of the vasculature in an illustrative example of adult mouse; b) Computational model of the aorta and main branches built from the cast; c) Regional biaxial tissue properties in the ATA, DTA, SAA, IAA, and CCA locations, mapped to the mouse-specific geometry; d) ATA catheter model; e) ATA+Femoral catheter model; f) DTA catheter model.

Figure 2

Computed hemodynamics for the baseline model. Comparison between in vivo and computed central aortic pressure: the heart model was tuned to reproduce the in vivo pressure (top left). Computed values of PWV based on pressure waves computed at two specific locations, P₁ and P₂ (bottom left). Center: Computed maps of blood pressure, wall shear stress, and blood velocity at peak systole. Right: Illustrative computed flow waveforms at multiple sites along the mouse arterial tree.

Figure 3

Comparison of hemodynamics at three sites (in the ATA, in the DTA, and near the aorto-iliac bifurcation – Bif) in the baseline, ATA catheter, ATA+Femoral catheter, and DTA catheter models.

Figure 4

Comparison of flow splits for the baseline, ATA catheter, ATA+Femoral catheter, and DTA catheter models. The top plot provides total flows to different branches; the bottom plot shows differential splits as fold changes with respect to the baseline model for each catheter model.

Figure 5

a) Comparison of aorto-iliac PWV in the baseline, ATA catheter, ATA+Femoral catheter, and DTA catheter models, where the percent change is given with respect the baseline model (upper part); comparison of PWV measured by the catheters sensors in each feasible case, compared with the baseline model (bottom part); b) Comparison of computed local PWV in the baseline, ATA catheter, ATA+Femoral catheter, and DTA catheter models

Figure 6

Control volume for the Bramwell and Hill analysis; volume and pressure are shown in systolic and diastolic configurations.