CARD21: The Effect of Drainage Cannula Design and Tip Position on Thrombosis Risk During Venoarterial Extracorporeal Membrane Oxygenation: A Computational Analysis

Background: Venoarterial extracorporeal membrane oxygenation (VA ECMO) supports critically ill patients with refractory cardiopulmonary failure. Drainage cannulae remove venous blood from the patient, but variability in cannula selection and tip position may impact flow dynamics and thrombosis risk. Therefore, this study investigated the effect of tip position of single-stage (SS) and multi-stage (MS) VA ECMO drainage cannulae on the risk of thrombosis. Methods: Computational fluid dynamics was used to model flow dynamics within a patient-specific geometry of the venae cavae. The tip of the SS and MS cannulae was modelled in the superior vena cava (SVC), SVC-Right atrium (RA) junction, mid-RA, inferior vena cava (IVC)-RA junction, and IVC. Constant mass flow rates were applied at all major vein inlets reflecting normal physiological flows. Drainage flow rates of the cannula were set at a constant 4 L/min throughout all simulations. The risk of thrombosis was assessed by measuring blood residence time, stagnant volume, rate of blood washout, and high wall shear stress. Results: Changes in the tip position of the SS cannula resulted in variability of thrombosis risk, whereas the MS cannula showed similar thrombosis risk during all simulations. The SS cannula showed reduced thrombosis risk arising from stagnant regions when placed in the SVC or SVC-RA junction, whereas an MS cannula was predicted to create stagnant regions during all tip positions (Figure 1). Conversely, the risk of thrombosis was increased in all positions with the SS cannula arising from higher maximum wall shear stresses (Table 1). When positioned in the IVC-RA junction and IVC, the SS cannula exhibited higher risk of thrombosis arising due to both high and low shear, compared to the MS cannula. Conclusion: Tip position of the drainage cannula impacts cannula flow dynamics and, subsequently, the risk of thrombosis. The use of MS cannulae can reduce high shear-related thrombosis, but SS cannulae can eliminate stagnant regions when advanced into the SVC. Therefore, the choice of cannula design and tip position should be carefully considered during cannulation.Figure 1. Comparison of stagnation regions between the single-stage (a) and multi-stage (b) cannulae at varying tip positions.