Fluid Dynamics of the Human Left Atrium under Simulated Normal and Atrial Fibrillation Conditions: A in vitro Tomographic PIV Study

Atrial fibrillation (AFib) is the most common cardiac arrhythmia in the US. AFib-induced flow changes would cause thromboembolism events inside the left atrium (LA), leading to a significantly increased risk of stroke. In this study, we performed an in vitro experimental flow study to quantitatively characterize the pulsatile flow in a left atrium model under normal and AFib conditions using tomographic Particle Image Velocimetry. The flow boundary conditions were numerically simulated via a system-level Windkessel model and validated using the clinical literature data. The experimental flow was then generated using a programmable closed-loop pulsatile flow simulator. The results show that the transient flow structures are highly three-dimensional and time-dependent in the left atrium chamber due to the complex inlets and the flow waveforms. The four pulmonary-vein-inlet jets give rise to a large vortical flow structure, which gains energy during systole and then dissipates during diastole. Compared with the “double-peak” flow waveform of the normal healthy LA, the “single-peak” AFib waveform causes a loss of flow momentum towards the end of the cycle. The results imply the important role of the lost pulsatility in the AFib-related flow stasis and pathology.