Abstract: Objective This study was designed to investigate left atrial appendage (LAA) size and morphology characteristics in patients with non-valvular atrial fibrillation (NVAF) by enhanced cardiac computed tomography (CT) scanning, and to evaluate the predictive value of these parameters for thromboembolic risk. MethodsA total of 189 NVAF patients were prospectively enrolled during December 2012 to January 2014 in West China Hospital of Sichuan University. Fifty-two atrial tachycardia patients without organ dysfunction were also recruited as controls. All subjects were scheduled for radiofrequency ablation and underwent enhanced cardiac CT scan. The clinical characteristics, comorbid diseases, anticoagulant therapy, and AF chronicity were collected and CHA₂DS₂-VASc score was calculated for the assessment of thromboembolic risk. The NVAF cohort was also divided further into LAA thrombus present (n=13) and absent (n=176) subgroup according to LAA with thrombus or not. Differencesin size and morphology characteristics of the LAA were compared among controls and different CHA₂DS₂-VASc thromboembolic risk subgroups, and between LAA thrombus and non-thrombus group. In addition, logistic regression analysis was used to identify whether these parameters predict thrombus formation independent of the CHA₂DS₂-VASc score in NVAF patients. ResultsCompared with controls, NVAF patients had significantly bigger orifice size. Windsock and cactus-type LAA were main morphology in controls, while the distribution of the four kinds of LAA types were similar in NVAF patients. The orifice and volume of the LAA were increased with increasing CHA₂DS₂-VASc riskscore, and chicken wing-type LAA was the predominant prevalence in low-intermediate thromboembolic risk subgroup while cauliflower in high thromboembolic risk subgroup. Compared with non-thrombus patients, LAA-thrombussubgroup exhibited a significantly increased orifice and volume, and higher prevalenceof the cauliflower shaped LAA. Logistic regression showed that the LAA orifice and cauliflower shape were independent predictors for thrombus formation in patients with NVAF following adjustment for the CHA₂DS₂-VASc score. ConclusionCardiac images obtained with CTis feasible for the analysis of LAA size and morphology, and these parameters provide incremental value in assessing the LAA thrombus risk in patients with NVAF.