Objectives-The purpose of this study was to investigate the importance of an adequately performed Valsalva maneuver for detecting a right-to-left shunt indicating reopening of the functional closure of the foramen ovale. Methods-We prospectively analyzed 260 patients (102 women and 158 men; mean age +/- SD, 41 +/- 19 years; range, 13-83 years) who underwent transesophageal echocardiography and agitated saline injection. Two-dimensional echocardiography, color Doppler imaging, and microbubbles were used to detect right-to-left shunts, and the Valsalva maneuver was performed to determine whether the functional closure of the foramen ovale had reopened. Results-Transesophageal echocardiography with color Doppler imaging identified a patent foramen ovale in 20 patients: 18 patients with a patent foramen ovale had left-to-right shunts, and 2 patients with atrial septal defects had bidirectional shunts. Both patients with atrial septal defects showed right-to-left shunt microbubbles without and with the Valsalva maneuver, whereas all 18 patients with a patent foramen ovale showed right-to-left shunt microbubbles only after the Valsalva maneuver. Foramen ovale reopening was identified by transesophageal echocardiography in an additional 40 patients with no shunt during rest on agitated saline injection and in whom the right-to-left shunt appeared only after the Valsalva maneuver. The Valsalva maneuver could cause an atrial septal swing, and its sensitivity and specificity were 100%. Conclusions-An adequately performed Valsalva maneuver is important for detecting a right-to-left shunt indicating reopening of the functional closure of the foramen ovale.