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Although paroxysmal atrial fibrillation (PAF) is an important cause of cardioembolic stroke, in contrast to chronic AF patients, the anatomical features of the left atrial appendage (LAA) in PAF patients remain unknown. Here, we investigated differences in LAA structures in patients with PAF and those with normal sinus rhythms (NSR) using 3D-computed tomography (3D-CT), which allows us to visualize complicated LAA structures at high spatial resolution. Study subjects were 30 consecutive PAF and 30 NSR patients with complete enhanced cardiac 3D-CT images available. After reconstruction of 3D LAA images, anatomical parameters of the LAA were measured and compared according to three proposed definitions of the LAA orifice plane determined by the following anatomical landmarks: DEF#1, center of warfarin ridge and centerline of proximal left circumflex artery; DEF#2, slope of warfarin ridge and mitral valve annulus; DEF#3, observers' discretion by progressive rotation using the observers' best estimate without the use of landmarks. The LAA volumes of the PAF groups were significantly greater than the NSR group according to all 3 definitions (DEF#1: 1.43 times, DEF#2: 1.44 times, and DEF#3: 1.36 times greater). The LAA orifice area was significantly larger in PAF than in NSR according to DEF#2, but was similar by DEF#1 and DEF#3. Intra-observer and inter-observer variations for any LAA measurements were very low. In conclusion, 3D-CT-based quantitative assessment of the LAA provides highly reproducible and detailed measurements, which can successfully discriminate differences of LAA volume between patients with NSR and those with PAF, suggesting significantly greater volumes in the latter.

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