Computational fluid dynamics of the right atrium: Assessment of modelling criteria for the evaluation of dialysis catheters

Abstract

Central venous catheters are widely used in haemodialysis therapy, having to respect design requirements for appropriate performance. These are placed within the right atrium (RA); however, there is no prior computational study assessing different catheter designs while mimicking their native environment. Here, a computational fluid dynamics model of the RA, based on realistic geometry and transient physiological boundary conditions, was developed and validated. Symmetric, split and step catheter designs were virtually placed in the RA and their performance was evaluated by: assessing their interaction with the RA haemodynamic environment through prediction of flow vorticity and wall shear stress (WSS) magnitudes (1); and quantifying recirculation and tip shear stress (2). Haemodynamic predictions from our RA model showed good agreement with the literature. Catheter placement in the RA increased average vorticity, which could indicate alterations of normal blood flow, and altered WSS magnitudes and distribution, which could indicate changes in tissue mechanical properties. All designs had recirculation and elevated shear stress values, which can induce platelet activation and subsequently thrombosis. The symmetric design, however, had the lowest associated values (best performance), while step design catheters working in reverse mode were associated with worsened performance. Different tip placements also impacted on catheter performance. Our findings suggest that using a realistically anatomical RA model to study catheter performance and interaction with the haemodynamic environment is crucial, and that care needs to be given to correct tip placement within the RA for improved recirculation percentages and diminished shear stress values.

Impact of altered vena cava flow rates on right atrium flow characteristics

“…These results reflect the commonly observed single vortex pattern in the body of the atrium, though generally this is described as a clockwise rotation ( 5 , 10 ). The same counterclockwise structure has however been reported in previous CFD ( 29 , 30 ) and imaging studies, where it was more prevalent (20.5%) in older patients (60–80 yr). Why the smaller auricle structure has not been reported in previous 4-D-MRI studies is likely due to the comparatively low spatial resolution of 4-D-MRI.…”

“…A counter-rotating vortex then results in the right auricle. Vorticity magnitude has been reported previously to quantify the rotational nature of the flow in the RA, though no distinction was made between the flow structures that direct blood toward the tricuspid valve and counterproductive vortical structures ( 29 ). Here, we take a common vector component ( Fig.…”

“…However, the limited imaging domain (240 mm inferior-superior) in the study meant that the origin of this helicity was unclear. Past CFD ( 29 , 30 ) and benchtop experiments ( 31 ) in the RA have been based on similar imaging domains requiring truncation of the SVC and IVC in reconstructions and these have not made mention of such helicity. Helical flow in both vena cava was again visible in the results of the present study.…”

An Inexpensive Cardiovascular Flow Simulator for Cardiac Catheterization Procedure Using a Pulmonary Artery Catheter

“…To do these theoretical calculations, we considered a Newtonian fluid–since we used water (μ = 1.0 cP) in our device–and found a value for each tube (SVC, IVC, and IN) at each time where F was the flow rate at that time and r was the radius of the tube ( Supplementary Tables 2 , 3 ) ( 32 , 33 , 44 , 45 ).…”

Data_Sheet_1.docx

“…To do these theoretical calculations, we considered a Newtonian fluid-since we used water (µ = 1.0 cP) in our device-and found a value for each tube (SVC, IVC, and IN) at each time where F was the flow rate at that time and r was the radius of the tube (Supplementary Tables 2, 3) (32,33,44,45).…”