Left atrial appendage shape impacts on the left atrial flow hemodynamics: A numerical hypothesis generating study on...

Area of Science:

• Cardiovascular Physiology
• Medical Imaging
• Computational Fluid Dynamics

Background:

• The left atrial appendage (LAA) is a primary site for thrombus formation in patients with atrial fibrillation (AF).
• LAA morphology, including shape, size, and volume, influences therapeutic option effectiveness.
• Understanding blood flow dynamics within the LAA is crucial for predicting thrombosis risk.

Purpose of the Study:

• To investigate blood flow patterns within the LAA using computational fluid dynamics (CFD).
• To evaluate the effects of LAA removal on blood flow dynamics in different patient morphologies.
• To correlate LAA morphology with the risk of thrombus formation under AF conditions.

Main Methods:

• 3D reconstruction of left atrium (LA) and LAA geometries from patient CT scans.
• CFD simulations were performed with imposed mitral valve outflow velocities for sinus rhythm (SR) and AF.
• Simulations were conducted on models with and without the LAA to assess removal effects.

Main Results:

• AF conditions reduced velocity and vorticity within the LA for both patients.
• LAA removal showed varied effects: increased blood flow and vorticity in one patient under AF, decreased them in another patient under both AF and SR.
• Increased vorticity within the LAA under AF suggests a higher thrombus formation risk, particularly in specific morphologies; blood stasis was most common in the distal LAA.

Conclusions:

• LAA morphology is a critical determinant of thrombosis risk in AF, with high volume, low flow velocity, and bi-lobed structures increasing stasis likelihood.
• The impact of LAA removal on hemodynamics differs significantly between individuals, making it a complex therapeutic strategy.
• Generalizing LAA removal as a treatment requires further investigation due to patient-specific morphological variations.