Atrial fibrillation and patent foramen potentially share same atrial flow dynamic profile and thrombotic mechanism

An impairment of the left atrial function similar to that one generally observed by echocardiography in atrial fibrillation (AF) has been reported in patients with patent foramen ovale (PFO) and permanent right-to-left shunting (RLS) [ ]. Computational fluid dynamic (CFD) studies have suggested that in left atrial appendage (LAA) vortices generated in the chamber remain high strengths and with longer durations in patients with AF, inducing ineffective emptying of the blood in the atrium and appendage, which then lead to blood stagnation and subsequent thrombus formation [ ]. Moreover, atrial wall movement by high-frequency fibrillation had a large impact on the stagnation of blood flow. The relative residence time, which is an indicator of stagnation of blood flow, increase in the upper part of the LAA during AF. Atrial vulnerability and atrial abnormalities such as PFO and atrial septal aneurysm have been suggested to be associated in patients with cryptogenetic stroke [ ]. An anti-arrhythmic effect has been postulated for transcatheter PFO closure [ ]. In the present manuscript, we want to characterize by means of CFD analysis the fluid dynamic profile of patients with mild RLS and permanent RLS evaluating if similarities with the fluid dynamic profile of patients with AF do eventually exist. The geometrical model of the right atrium (RA), left atrium (LA), left atrial appendage (LAA) and PFO has been constructed based on the collective data acquired using cardiac Magnetic Resonance Imaging in 100 patients (mean age 39.5 ± 7.4 years) with permanent RLS or mild RLS on transesophageal echocardiography investigated as part of PFO management program in our institution. Specifically, the entire domain has been reconstructed and meshed using the Rhinoceros v. 4.0 Evaluation software (McNeel& Associates, Indianapolis, IN). Pulmonary veins are located at the back of the atrium, two on each side at different heights. The appendage model used in this has been modelled based on the data acquired from Ernst et al. with three lobes [ ]. Blood was modelled as a non-Newtonian, viscous and incompressible fluid and represented using the Navier-Stokes and continuity equation. Simulations were conducted using the commercial software ANSYS FLUENT 14.0 (Ansys, Inc., Canonsburg, PA) and flows have been analysed in diastole.