Left atrial enlargement and non-paroxysmal atrial fibrillation as risk factors for left atrial thrombus/spontaneous Echo contrast in patients with atrial fibrillation and low CHADS-VASc score.

Objective: To determine the risk factors for thromboembolism in lower risk patients with non-valvular atrial fibrillation (AF) and low CHADS-VASc scores, which remain undefined.

Methods: We retrospectively analyzed the baseline clinical characteristics, routine laboratory parameters, and echocardiographic measurements of 705 patients (71.1% male; mean age: 52.10 ± 9.64 years) with low CHADS-VASc score (0 or 1; 1 point for female sex) out of 1346 consecutive patients with non-valvular AF who underwent transesophageal echocardiography (TEE) at Guangdong Cardiovascular Institute between January 2013 and December 2015.

Results: Patients with left atrial thrombus (LAT) or spontaneous echo contrast (SEC) on TEE (24/705, 4%) showed a higher incidence rate of vascular disease (54.2% . 32.9%, = 0.045) and non-paroxysmal AF (79.2% . 29.4%, < 0.001), larger left atrial diameter (43.08 ± 4.59 . 36.02 ± 5.53 mm, < 0.001), and lower left ventricular ejection fraction (58.23 ± 8.82% . 64.15 ± 7.14%, < 0.001) than those without. Multivariate logistic regression analysis identified left atrial diameter [odds ratio (OR) = 1.171, 95% confidence interval (CI): 1.084-1.265, < 0.001] and non-paroxysmal AF (OR = 3.766, 95% CI: 1.282-11.061, = 0.016) as independent risk factors for LAT/SEC. In ROC curve analysis, a left atrial dimeter cutoff of 37.5 mm yielded 95.0% sensitivity and 62.7% specificity (AUC: 0.847, < 0.0001, 95% CI: 0.793-0.914).

Conclusion: In patients with non-valvular AF with low CHADS-VASc score, the presence of LAT or SEC was associated with left atrial enlargement, which had moderate predictive value, and non-paroxysmal AF.