Pulmonary vein flow split affects left atrial appendage stasis in patient-specific CFD simulations

Blood flow inside the left atrium (LA) is associated with severe cardiovascular events like embolic stroke. Patient-specific CFD simulations predict LA hemodynamics and blood stasis in the left atrial appendage (LAA), the preferred thrombosis site. In these simulations, patient-specific LA geometry and transmitral flow rates can be extracted from 4D anatomical images. However, the flow rates through the pulmonary vein (PV) inlets are a source of uncertainty because they need to be modeled. We studied how the flow split between the left and right PVs affects LA blood flow in 14 patients (11 in sinus rhythm, 3 in AF) using an in-house immersed boundary solver. We considered even flow split as customary in the literature as well as the more physiological 45-55% and 40-60% splits. We found that PV flow split affects the LA body's mean flow pattern qualitatively and the LAA residence time (RT) quantitatively. However, the LAA RT dependence on PV flow split was comparable to its beat-to-beat variability, suggesting that the PV flow split might not be a critical source of uncertainty as long as this parameter is kept within the general physiological range.