Background: Ventricular torsion is important in assessment of the systolic and diastolic function especially in single ventricle (SV) but is poorly studied. Objective: We aimed to a) examine serial changes in SV torsion, and b) examine its association with CMR data and exercise performance. Methods: We retrospectively studied SV patients after Fontan completion. Speckle-tracking echocardiography was used to evaluate serial changes in ventricular mechanics; strain, torsion, and untwist. CMR volumetric data and cardiopulmonary exercise data closest to echocardiograms were obtained. The most recent follow up echocardiographic and CMR data were compared to data before Fontan. Results: 45 SV patients (27 LV, 12 RV, and 6 co dominant) were studied. Demographics, echocardiographic, CMR, and exercise data are shown in table 1. Mean time at follow up echo from time of Fontan was 12.8 (10.6-16.6) years. Follow up echocardiograms showed reduced global longitudinal strain [-17.5(-6.5 to-19.5) vs -19.8 (-12 to -23%), p=0.01], circumferential strain [-15.7 (-8.4 to - 20.7) vs [-18.9 (-11.2 to -25.0), p=0.009], reduced torsion [5.5°/cm (-6.1 to 17.8) vs 8.1°/cm (-9.7 to18.5) vs, p=0.03], decreased apical rotation [6.5°/cm (-11.3 to 18.1) vs 5.1°/cm (-21.2 to 19.7), p=0.02] with no significant change in basal rotation compared to the echo at time of Fontan. Single RV had lower net torsion compared to single LV [2.7°/cm (-2.5.1 to 13.1) vs 6.1°/cm (-6.3 to 19.5) vs, p=0.03]. Mean interval between echocardiograms and exercise testing and CMR were 3.5±2.2 and 5.6±1.8 months respectively. Torsion and untwist rates correlated with peak oxygen consumption (r=0.64, -0.41, p=0.01, 0.04 respectively) but did not correlate with ventricular volumes or ejection fractions. Conclusion: In long term follow up post Fontan, SV torsion is decreased due to decreased apical rotation, worse in single RV, and is associated with decreased exercise capacity.