E1710. Left Atrial Appendage Occlusion Reduces Flow Stasis and Thrombogenicity: A Proof-of-Concept Using 4D Flow MRI
  1. Min Jae Cha; Chung-Ang University Hospital - Radiology
  2. Don-Gwan An; Hanyang University - Mechanical Convergence Engineering
  3. Seung Yong Shin; Chung-Ang University Hospital - Internal Medicine
  4. Simon Song; Hanyang University - Mechanical Convergence Engineering
Little is known about the actual flow dynamic changes within the left atrium (LA) before and after percutaneous left atrial appendage occlusion (LAAO) in patients with atrial fibrillation (AF). We aimed to evaluate LA flow dynamics for pre-occluded, correctly occluded, and incorrectly occluded LAAs in patients with AF via four-dimensional (4D) flow magnetic resonance imaging (MRI) and 3D printed phantoms.

Materials and Methods:
Life-sized 3D printed LA phantoms—including pre-, correctly, and incorrectly occluded models—of an 86-year-old patient with long-standing persistent AF were constructed based on cardiac computed tomography images. A custom-made, closed-loop flow circuit was set, and pulsatile pulmonary venous flow was delivered by pump. 4D flow MRI was obtained using a 3-tesla scanner, and was analyzed using MATLAB-based software. Flow metrics associated with blood stasis and thrombogenicity, such as the volume of stasis defined by velocity threshold (|V| < 3 cm/s), time-averaged wall shear stress (WSS), and endothelial cell activation potential (ECAP), were analyzed and compared among three conditions.

Different spatial distributions, orientations and magnitudes of flow were directly visualized within the three LA phantoms using 4D flow MRI. The time-averaged volume and percentage of LA flow stasis were consistently minimized in the correctly occluded model (70.82 ml, 38.97%), followed by the incorrectly occluded (73.17 ml, 39.02%) and pre-procedural (79.11 ml, 39.71%) models. The pre-occluded model was associated with the lowest surface-and-time-averaged WSS (0.048 Pa), followed by incorrectly (0.059 Pa) and correctly (0.072 Pa) occluded models. Conversely, ECAP was lowest in the correctly occluded model (4.004 Pa-1), followed by the incorrectly- (4.792 Pa-1) and pre-occluded (5.861 Pa-1) models.

These findings suggest that correctly occluded LAAs may guarantee a maximal reduction in LA flow stasis and thrombogenicity, presenting a tentative procedural goal to maximize clinical benefit in patients with AF.