Left atrium hemodynamic in atrial fibrillation and normal subjects

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Background A computational fluid-dynamics (CFD) model previously developed with the aim of evaluating cardioembolic risk in patient affected by atrial fibrillation (AF) was used for the characterization of the left atrium (LA) hemodynamic in normal subjects (NL), patients affected by paroxysmal atrial fibrillation (PAR-AF) and patients affected by persistent atrial fibrillation (PER-AF). Based on the fluid-dynamics simulations results, we aimed at enhancing differences in blood flow in AF patients and NL and at better understanding the relationship between AF progression and stroke risk on a patient-specific basis. Methods 3D patient-specific anatomical and motion models were derived from ECG-gated coronary artery CT acquired with retrospective protocol. These models represented the computational domain for CFD simulations in which inflow initial conditions were derived from PW Doppler at the mitral valve and at the pulmonary veins. Velocity field and vortex structures both within the LA and left atrial appendage (LAA) were assessed in 10 NL, 5 PAR-AF and 4 PER-AF. Blood stasis was evaluated by populating the LAA with 500 particles and counting the number of particles still present after five cardiac cycles. Results Velocities inside the LA and in the LAA presented different amplitude and distribution in the 3 groups (peak velocity – NL: 50÷60 cm/s, PAR-AF: 40÷50 cm/s, PER-AF: 15÷25 cm/s). The mean velocity resulted lower in the PER-AF compared with PAR-AF (mean velocity – PAR-AF: 25÷35 cm/s, PER-AF: 8÷20 cm/s) at the LAA ostium and inside the LAA, in which the wash-out effect was strongly reduced (Figure 1). On the other hand, the mean velocity in the NL was higher with respect of AF patients (mean velocity – NL: 40÷45 cm/s). A higher number of vortex structures was observed in NL compared with AF patients, thus favouring the hypothesis of a more efficient wash-out of the LA and of the LAA. Blood stasis in terms of number of particles in the LAA after five cardiac cycles confirmed these results (NL: 5±2, PAR-AF: 18±3, PER-AF: 41±10). Conclusions The developed approach quantifies differences in LA hemodynamic between AF and NL patients, also allowing a stratification of the atrial disease progression in terms of variations in the blood velocity, organization of blood flow and quantification of blood stasis.