- Background Not all echo laboratories have the capability of measuring direct online 3D images, but do have the capability of turning 3D images into 2D ones “online” for bedside measurements. Thus, we hypothesized that a simple and rapid rotation of the sagittal view (green box, x-plane) that shows all needed left atrial appendage (LAA) number of lobes, orifice area, maximal and minimal diameters and depth parameters on the 3D transesophageal echocardiography (3DTEE) image and LAA measurements after turning the images into 2D (Rotational 3DTEE/“Yosefy Rotation”) is as accurate as the direct measurement on real-time-3D image (RT3DTEE). Methods We prospectively studied 41 consecutive patients who underwent a routine TEE exam, using QLAB 10 Application on EPIQ7 and IE33 3D-Echo machine (BORTHEL Phillips) between 01/2013 and 12/2015. All patients underwent 64-slice CT before pulmonary vein isolation or for workup of pulmonary embolism. LAA measurements were compared between RT3DTEE and Rotational 3DTEE versus CT. ResultsRotational 3DTEE measurements of LAA were not statistically different from RT3DTEE and from CT regarding: number of lobes (1.6 ± 0.7, 1.6 ± 0.6, and 1.4 ± 0.6, respectively, p = NS for all); internal area of orifice (3.1 ± 0.6, 3.0 ± 0.7, and 3.3 ± 1.5 cm2, respectively, p = NS for all); maximal LAA diameter (24.8 ± 4.5, 24.6 ± 5.0, and 24.9 ± 5.8 mm, respectively, p = NS for all); minimal LAA diameter (16.4 ± 3.4, 16.7 ± 3.3, and 17.0 ± 4.4 mm, respectively, p = NS for all), and LAA depth (20.0 ± 2.1, 19.8 ± 2.2, and 21.7 ± 6.9 mm, respectively, p = NS for all). Conclusion Rotational 3DTEE method for assessing LAA is a simple, rapid and feasible method that has accuracy similar to that of RT3DTEE and CT. Thus, rotational 3DTEE (“Yosefy rotation”) may facilitate LAA closure procedure by choosing the appropriate device size.