Background: Newly developed two-dimensional ultrasound speckle tracking imaging allows measurements of left ventricular rotation and torsion. There is little information about LV torsion (LVtor) in Fontan patients. The purpose of this study was to assess LVtor and untwisting in tricuspid atresia (TA) (type 1) patients after Fontan procedure. Methods: We acquired basal and apical LV short-axis images in asymptomatic 11 TA patients (age = 21짹7 yr, follow-up duration after Fontan operation = 16짹3 yr) and 11 healthy controls (age = 19짹8 yr). Using two-dimensional strain software, a time-domain speckle tracking was performed, and mean value of LVtor was obtained at each plane. LVtor was defined as the instantaneous net difference of the basal and apical rotation. Result: Six patients underwent atriopulmonary connections and 5 total cavopulmonary connections. LV ejection fraction and mitral annulus early diastolic velocity in TA patients were significantly decreased in comparisons with controls (58짹7% vs. 64짹4%; P=0.050, 12.1짹2.1 vs. 19.6짹2.2 cm/sec; P < 0.001). LV longitudinal strain and apical circumferential strain were also reduced (-16.3짹2.9% vs. -22.5짹2.0%.; P <0.001, -25.0짹10.8% vs. -32.9짹7.0%.; P= 0.055). Peak LVtor (16.1짹13.5 vs. 19.7짹5.5 degrees; P = 0.422), peak systolic twisting velocity (99짹57 vs. 125짹38 degrees/sec; P = 0.226), twisting rate (68짹45 vs. 84짹21 degrees/sec; P=0.303) and untwisting rate (71짹84 vs. 68짹42 degrees/sec; P=0.914) were similar between two groups. LVtor was significantly correlated with LV ejection fraction (R2=0.190, P=0.048). Conclusion: Although LV EF, LV longitudinal and LV circumferential strain in TA patients were significantly decreased, LV systolic torsion and diastolic untwisting in TA after Fontan procedure were preserved.