Background.This study examines whether real-time 3-dimensional echocardiography can provide an image resolution to serve as a substitute for optical visualization in performing mitral valve plasty.Methods.Three pigs were used in this study. A 3-dimensional echocardiographic system was evaluated on an epicardial surface. Beating heart mitral valve plasty was performed with a surgical stapler inserted from the apex of the left ventricle using only 3-dimensional echocardiographic visualization.Results.The high-quality images of the mitral valve were obtained with the probe at the epicardial position. However, by inserting the surgical instrument into the left ventricle, an acoustic shadow developed on the images. The images became indistinct because of the acoustic shadow, and operation became difficult. For the mitral valve plasty, an edge-to-edge mitral valve repair was carried out using a stapler (10 mm) under the beating heart. The stapler was confirmed to seize both leaflets evenly in only 1 of the 3 pigs.Conclusions.Real-time 3-dimensional echocardiography provided clear 3-dimensional images of the mitral valve; however, when a surgical instrument was inserted into the left ventricle, an acoustic shadow appeared on the image and made detailed confirmation difficult. Lessening or eliminating the acoustic shadow would be a key point to improve this procedure.