SummaryThe left atrial appendage (LAA) represents one of the major sources of cardiac thrombi responsible for embolic stroke in patients with atrial fibrillation (AF). The aim of the present study was to evaluate LAA structure and functions by transesophageal echocardiography (TEE) in patients with AF to investigate the possible association between the different LAA morphologies and the patients' history of ischemic cerebral stroke. We included 50 patients with non-valvular AF (29 chronic, 21 paroxysmal), 24 patients (13 men) without stroke; and 26 patients (9 men) with a history of ischemic stroke. All patients underwent TEE evaluation of LAA morphology and functions. Compared to patients without stroke, patients with ischemic stroke had significantly higher CHADS2 scores (4.19 ± 0.89 versus 1.67 ± 1.13; P < 0.001) and C-reactive protein levels (8.3 ± 1.6 versus 7.6 ± 0.83 mg/L; P = 0.023), and lower peak filling (21.7 ± 11.3 versus 31.2 ± 9.5 cm/second; P = 0.033) and emptying (22.2 ± 9.7 versus 33.4 ± 13.4 cm/second, P = 0.030) velocities. Triangular LAA morphology had a higher prevalence in patients with stroke (36% versus 12% in non-stroke group); and in half of them an LAA thrombus was present. LAA thrombi were detected in 9 patients (18%) with stroke and in 5 patients (10%) Approximately 33% of arrhythmiarelated hospitalizations are for AF, which is also associated with a 5-fold increase in the risk of stroke and 2-fold increase in the risk of all cause mortality. 1) AF causes 15-20% of ischemic strokes, and the annual risk of stroke in patients with nonvalvular AF is as high as 5%.2)The left atrial appendage (LAA) has been described as a long, narrow, tubular, wavy, hooked structure with different lobes and a narrow junction and crenellated lumen. 3,4) As the LAA represents one of the major sources of cardiac thrombus formation responsible for stroke in patients with AF, 5,6) the imaging of the different structures and lobes is of utmost importance to diagnose the presence of thrombus, especially in patients with non-valvular AF. 7,8) Multidetector computed tomography 9) and contrast-enhanced magnetic resonance imaging 10) are able to image the LAA; however, it was concluded that magnetic resonance imaging lacks diagnostic accuracy for the detection of LAA thrombi.10) Transesophageal echocardiography (TEE) is the gold standard to detect LAA thrombus, 11) but false positive results still occur.12) In this study, we evaluated the LAA structure and functions by TEE in patients with non-valvular AF (both chronic and paroxysmal types) to study the possible association between the different LAA morphologies and functional changes with the patients' history of ischemic cerebral stroke. MethodsStudy design and participants: This study was conducted on 50 patients with non-valvular AF; including both chronic (29 patients, 58%) and paroxysmal (21 patients, 42%) cases. We included patients with documented paroxysmal AF because large, prospective studies have shown that the risk for thromboembolism does not differ ...