Motion of left atrial appendage as a determinant of thrombus formation in patients with a low CHADS2 score receiving warfarin for persistent nonvalvular atrial fibrillation

LAA emptying fraction (EF) and LAA peak longitudinal strain were measured by VVI using transesophageal echocardiography in 260 consecutive patients with nonvalvular persistent AF receiving warfarin. The patients were divided into two groups according to the presence (n=43) or absence (n=217) of LAA thrombus. Moreover, the patients within each group were further divided into subgroups according to a CHADS2 score ≤1.Multivariate logistic regression analysis showed that LAAEF was an independent determinant of LAA thrombus in the subgroup of 140 with a low CHADS2 score. Receiver operating characteristics curve analysis showed that an LAAEF of 21% was the optimal cutoff value for predicting LAA thrombus.LAA thrombus formation depended on LAA contractility. AF patients with reduced LAA contractile fraction (LAAEF ≤21%) require strong anticoagulant therapy to avoid thromboembolic events regardless of a low CHADS2 score (≤1).Left atrial appendage (LAA) thrombus in patients with atrial fibrillation (AF) is a high risk factor of cardiogenic thromboembolism, and causes stroke at the rate of 1.5 - 3.4% per year even in patients receiving warfarin [1-3]. Establishment of optimal risk stratification and therapeutic strategies is the best hope for decreasing the burden of AF-related thromboembolism. The international normalized ratio of prothrombin time (PT-INR) is used as an index for optimal anticoagulation therapy, and the CHADS2 (congestive heart failure, hypertension, age ≥75？years, diabetes mellitus, and prior stroke or transient ischemic attack) score is widely used for risk stratification of thrombus in clinical practice [4,5]. However, it was reported that some AF patients that have PT-INR within the therapeutic range or a low CHADS2 score still suffer from thromboembolism [6].As for ultrasound parameters, spontaneous echo contrast (SEC) and LAA peak emptying flow velocity (LAAPV) have been proposed as echocardiographic predictors of LAA thrombus [7,8]. However, the optim