Background. An impairment of the left atrial function similar to that usually observed in atrial fibrillation (AF) has been observed also in patients with patent foramen ovale (PFO) and permanent right-to-left shunting (RLS) Methods. We reconstructed the geometrical model of right atrium (RA), PFO, left atrium (LA) and left atrial appendage (LAA) of 65 patients with mild (36 patients mean age 45.5±6.8 years, 24 females) or permanent (29 patients, mean age 45.1±5.3 years, 21 females) RLS using anatomical data obtained by transoesophageal echocardiography (TEE) and cardiac MRI, performed as a part of our institutional screening protocol for paradoxical embolism. Using computational fluid dynamic analysis (CFD) we assessed the vorticity magnitude in both the LA and LAA to analyse a possible rheological relationship between PFO and AF. Results. The anatomical models, in terms of dimensions, were comparable among the patients with mild and permanent RLS. A higher vorticity magnitude was observed in the mild shunt both in the LA (101.12±21.3 vs 88.3±22.6, p=0.02) and LAA (62±14.4 vs 32.4±12.3, p<0.01) when compared to the permanent R-L shunting. Conclusions. The lower vorticity magnitude across the LA and LAA in patients with permanent RLS suggests a possible higher stagnation of the blood in these anatomical sites, similarly as previously observed in patients with AF.