PURPOSE: To assess by cardiovascular magnetic resonance (CMR) and CMR tagging if the Amplatzer Septal Occluder affects right ventricular (RV) and left ventricular (LV) motion pattern. MATERIALS AND METHODS: Sixteen consecutive patients with significant atrial septal defect (ASD) and nine consecutive patients with persistent foramen ovale (PFO) as controls were studied before and a median of 14 days after defect closure by an Amplatzer occluder. By CMR end-diastolic (EDV) and end-systolic (ESV) RV and LV volumes were determined. Aortic and pulmonary artery flow was measured for assessment of left-to-right shunt (Qp/Qs). By CMR tagging circumferential strain and radial shortening, maximal rotation and torsion were measured, RESULTS: In ASD patients RV-EDV and RV-ESV decreased (P < 0.05). LV-EDV and LV-ESV increased after ASD closure (P < 0.005). Qp/Qs dropped from 1.8 to 1.0 (P < 0.001). PFO patients showed no ventricular volume change after PFO closure. In ASD patients circumferential strain and radial shortening and maximal rotation of the RV decreased by ASD closure (P < 0.01). In LV only maximal rotation at the base and apex decreased significantly (P < 0.05). Torsion remained constant. In PFO patients no tagging parameter changed after defect closure. CONCLUSION: The Amplatzer occluder itself does not change the ventricular contraction pattern. All volume and myocardial deformation changes were caused by ventricular loading shifts. J. Magn. Reson. Imaging 2012;. © 2012 Wiley Periodicals, Inc.