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Purpose: The presence of thrombi, spontaneous echo contrast (SEC), increased LAA area and low emptying velocities have been associated with increased cardioembolic risk. Nevertheless these markers assess indirectly LAA contractile function. Speckle tracking (ST) imaging is a novel echocardiographic modality that can quantify global and regional contractility of cardiac chambers. The aim of the present study was to assess LAA contractility and size using ST derived indices and assess their correlation with traditional markers of LAA/LA function.Methods: Eighty two consecutive patients (median age 65; male:female ratio 1.5), 40 in atrial fibrillation (AF) and 42 in sinus rhythm that underwent TEE for a variety of indications were recruited in the study. TEE was performed with the MyLab60 echocardiographic system (Esaote, Italy). In all patients three cardiac cycles of the LAA assessed from mid esophageal, 2 chamber view were recorded and stored. Maximum LAA emptying velocity, LAA area, presence of LAA thrombi or SEC, LA area and volume, LA diameter from the parasternal long axis (PSLAx) view and A wave velocity were also recorded as indices of LA/LAA function. ST of the LAA was performed offline using the Qlab platform (Esaote, Italy). LAA maximum systolic volume, LAA ejection fraction (EF), longitudinal strain (LS) of the LAA free wall, LS of the LAA ventricular wall, and transverse displacement (TD) of the free and ventricular wall were assessed and recorded.Results: ST imaging was feasible in LAA and provided reproducible results regarding LAA volume, EF, LS and TD with inter and intraobserver variability >0.7 for every index that was assessed. Ventricular LAA wall peak diastolic LS and TD was lower in patients with AF compared with patients in sinus rhythm (p<0.01). Ventricular LAA wall peak diastolic LS was strongly associated with peak LAA emptying velocity (Spearman's rho=0.8; p<0.001) and significantly associated with LA volume, area and LAA area (Spearman's rho=0.63, 0.65 and 0.68 respectively). Similarly, ST-derived LAA, EF and LAA volume were significantly associated with conventional indices of LAA size and function (LA area, volume, LA PSLAx diameter; Spearman's rho>0.6 for all comparisons). Finally, LAA emptying velocity and LAA ventricular wall ST were both significantly associated with the presence of LAA thrombi and SEC (Spearman's rho=0.7 and 0.75 respectively).Conclusions: Speckle tracking derived indices of the LAA size and function are reproducible and easy to obtain. They significantly correlate with conventional markers of LAA performance and also with presence LAA thrombi and SEC.