Demonstration of Patient-Specific Simulations to Assess Left Atrial Appendage Thrombogenesis Risk.

Manuel García-Villalba,Pablo Martinez-Legazpi,Andrew M Kahn,Juan C Del Álamo,Javier Bermejo,Lorenzo Rossini,Davis Vigneault,Elliot Mcveigh,Alejandro Gonzalo,Eduardo Durán,Oscar Flores

doi:10.3389/fphys.2021.596596

Abstract

Atrial fibrillation (AF) alters left atrial (LA) hemodynamics, which can lead to thrombosis in the left atrial appendage (LAA), systemic embolism and stroke. A personalized risk-stratification of AF patients for stroke would permit improved balancing of preventive anticoagulation therapies against bleeding risk. We investigated how LA anatomy and function impact LA and LAA hemodynamics, and explored whether patient-specific analysis by computational fluid dynamics (CFD) can predict the risk of LAA thrombosis. We analyzed 4D-CT acquisitions of LA wall motion with an in-house immersed-boundary CFD solver. We considered six patients with diverse atrial function, three with either a LAA thrombus (removed digitally before running the simulations) or a history of transient ischemic attacks (LAAT/TIA-pos), and three without a LAA thrombus or TIA (LAAT/TIA-neg). We found that blood inside the left atrial appendage of LAAT/TIA-pos patients had marked alterations in residence time and kinetic energy when compared with LAAT/TIA-neg patients. In addition, we showed how the LA conduit, reservoir and booster functions distinctly affect LA and LAA hemodynamics. Finally, fixed-wall and moving-wall simulations produced different LA hemodynamics and residence time predictions for each patient. Consequently, fixed-wall simulations risk-stratified our small cohort for LAA thrombosis worse than moving-wall simulations, particularly patients with intermediate LAA residence time. Overall, these results suggest that both wall kinetics and LAA morphology contribute to LAA blood stasis and thrombosis.

Highlights

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting approximately 35 million people worldwide (Benjamin et al, 2019)
Cardiac-gated cine computed tomography (CT) scans were acquired at the National Institutes of Health (NIH), Bethesda, Maryland (N = 3) and at the University of California San Diego (UCSD), CA, United States (N = 3)
The images were acquired with 3 different scanner models: 2 studies were obtained on a Siemens Force system, 3 studies were obtained on the Toshiba Aquillion ONE (1 and NIH, 2 at UCSD) and one study was obtained on the 256-slice GE Healthcare Revolution CT at UCSD

Summary

Introduction

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting approximately 35 million people worldwide (Benjamin et al, 2019). Each atrium has a morphologically characteristic body, and an appendage where thrombi form preferentially (Goette et al, 2017) Because some of these thrombi can travel to the brain, the risk of stroke of patients with AF is five times higher compared to the general population, and AF causes 15% of all strokes (Benjamin et al, 2019). Current methods to risk-stratify patients are not personalized and contain no information about the patients’ cardiac anatomy or blood flow; instead, they are based on demographic and clinical factors such as age, gender, or coexistent hypertension. These factors are derived from large clinical trials and have limited predictive value for a specific patient. There are currently many patients for whom there is clinical uncertainty as to whether anticoagulation is beneficial (January et al, 2014)

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