Myocardial deformation imaging is used to assess regional left ventricular (LV) function. We sought to define the impact of changes in LV loading conditions on myocardial deformation parameters. Aortic valve replacement in patients with different aortic valve pathologies was used as a model to assess the impact of preload and afterload changes. In 53 patients scheduled for aortic valve replacement serial echocardiographic studies were performed preoperatively and postoperatively (within 7 days and at 6 months). Parasternal short-axis views were acquired. Using novel computer software radial and circumferential strain and strain rate were determined as parameters of myocardial deformation for each segment of the LV and were subsequently averaged. Immediately postoperatively there was a relative increase of radial strain by 4.5 +/- 1.8% after valve replacement for aortic stenosis (AS) (P < .001), a relative decrease of 9.4 +/- 7.7% after valve replacement for aortic regurgitation (aortic insufficiency [AI]) (P < .001), and unchanged radial strain after valve replacement for AS and aortic regurgitation. During the subsequent 6 months of follow-up, there was additional relative increase of radial strain by 5.2 +/- 3.1% in the AS group (P < .001), by 12.0 +/- 13.7% in the AI group (P < .01), and by 5.6 +/- 3.4% in the AS and AI group (P < .001). Similar changes were observed for the other strain and strain rate parameters. In conclusion, myocardial deformation parameters change significantly immediately after aortic valve replacement for AS or AI indicating a dependency of determined myocardial deformation parameters on LV preload and afterload.