Association of atrial fibrosis quantified using LGE-MRI with atrial appendage thrombus and spontaneous contrast on transesophageal echocardiography in patients with atrial fibrillation

Abstract

Introduction: Transesophageal echocardiography (TEE) is used to evaluate for left atrial appendage (LAA) thrombi prior to restoration of sinus rhythm in atrial fibrillation (AF). We examined the relationship of atrial fibrosis quantified using late gadolinium enhancement MRI (LGE-MRI) with TEE findings.

Methods and results: We included 178 patients with AF, undergoing TEE and LGE-MRI prior to ablation or cardioversion. LGE-MRI and subsequent image processing was used to quantify atrial fibrosis based on signal intensity analysis. The mean CHADS2 score was 1.24 ± 1.08 and CHA2 DS2 -VASc was 2.08 ± 1.33. The LAA was classified as normal, spontaneous echocardiographic contrast (SEC) present or thrombus present. LAA thrombus was found in 12 patients (6.7%) while SEC was identified in 19 patients (10.7%). Patients with thrombus had higher atrial fibrosis compared to patients without thrombus (26.9 ± 17.4% vs 16.7 ± 10.5%; P < 0.01). Atrial fibrosis was also higher in patients with SEC (23.3 ± 13.7%) compared to those without SEC (16.7 ± 10.8%; P = 0.01). Patients with high atrial fibrosis (>20%) were more likely to have a LAA thrombus (odds ratio 4.6; P = 0.02) and SEC (odds ratio 2.6; P = 0.06). Multivariate logistic regression showed high fibrosis (odds ratio 3.6; P < 0.01) and CHADS2 ≥2 (odds ratio 3.5; P < 0.01) were significant predictors of TEE abnormalities (LAA thrombus or SEC). The area under the curve for the model including high fibrosis, AF type and CHADS2 ≥2 or CHA2 DS2 -VASc ≥2 was 0.73 compared to 0.63 and 0.65 for CHADS2 and CHA2 DS2 -VASc alone.

Conclusions: Atrial fibrosis is independently associated with appendage thrombus and spontaneous contrast. It provides additional risk stratification not captured by clinical parameters.

Keywords: appendage thrombus; atrial fibrillation; catheter ablation; magnetic resonance imaging; stroke; transesophageal echocardiography.

© 2013 Wiley Periodicals, Inc.

Figures

Figure 1

Example of MRI image processing is shown for a patient with a quantified fibrosis of 13.0%. The steps from MRI image acquisition to quantification of fibrosis are illustrated.

Figure 2

Sample transesophageal echocardiographic still frames representing patients with a normal LA appendage, SEC and a LAA thrombus with their respective three-dimensional reconstructions illustrating atrial fibrosis derived from LGE-MRI imaging.