Abstract 15673: Structural Remodeling Determinants of Reduced Left Atrial Blood Flow Measured by 4D Flow MRI in Patients With Atrial Fibrillation
Introduction: Thromboembolism in patients with atrial fibrillation (AF) is due in part to reduced blood flow in the left atrium (LA).
Hypothesis: Using MR-based measures, we tested the hypothesis that AF patients with reduced LA flow are more likely to have a greater amount of structural remodeling characterized by larger LA volume and more LA fibrosis.
Methods: MRI data were obtained from 23 AF patients (18 male, 66±11 years old). Nine patients were in sinus rhythm and 14 were in AF at the time of the MRI. MR angiography was used to calculate LA volume. Delayed enhancement images were used to quantify the amount of fibrosis as a percentage of the total surface area of the LA. 4D flow MRI was used to measure the blood flow velocity and stasis (% of LA velocities <0.2 m/s) in the LA. The average of the top 50% of the flow velocities was used as the representative velocity measure. Linear regression was used to test the association between LA hemodynamics, LA volume and LA fibrosis.
Results: Compared with patients in sinus rhythm, patients in AF had larger LA volumes (117±14 vs. 69±11 mL, p=0.02) and trends for lower flow velocity (0.14±0.03 vs. 0.17±0.04 m/s, p=0.055) and more stasis (83±10 vs. 73±15%, p=0.054), but no difference in fibrosis (14.9±6.3 vs.12.3±4.3, p=0.29). Average flow velocity was negatively correlated with LA volume (R=-0.63, p=0.001) but not significantly correlated with LA fibrosis (R=-0.16, p=0.47). Similarly, the amount of stasis was significantly correlated with LA volume (R=0.59, p=0.003) but not with fibrosis (R=0.07, p=0.74).
Conclusions: Reduced blood flow in the LA in AF patients appear to be driven more by atrial size and AF itself rather than fibrotic structural changes. Further study is needed to determine how these MR measures can be used to assess risk for thromboembolism in patients with AF.
Author Disclosures: J. Ng: Research Grant; Significant; NIH. M. Markl: Research Grant; Significant; NIH. D.C. Lee: None. M.L. Carr: None. J.K. Ng: Research Grant; Significant; NIH. J.C. Carr: Research Grant; Modest; NIH. J.J. Goldberger: Research Grant; Significant; NIH.
- © 2014 by American Heart Association, Inc.