A 6-month-old girl (2.7 kg) diagnosed with PDA, ventricular septal defect, and accompanying pulmonary hypertension was scheduled for PDA ligation and PAB. Preoperative transthoracic echocardiography indicated the peak pressure gradient of a left-to-right PDA shunt as 14 mmHg. After induction of general anesthesia and tracheal intubation, a single-plane TEE probe (UST-52110S; Hitachi-Aloka Medical, Tokyo, Japan), connected to an ultrasound apparatus (Prosound F75; Hitachi-Aloka Medical), was inserted into the patient’s esophagus. The tip of this probe was 6.0, 13.4, and 5.3 mm in width, length, and depth, respectively. Hemodynamics and ventilation conditions were unchanged following probe insertion and manipulation. Before surgery initiation, TEE demonstrated a left-to-right shunt through the PDA on color Doppler flow imaging. Surgery was initiated under midline sternotomy, and the PDA was ligated using silk thread. After PDA ligation, disappearance of the PDA shunt flow was confirmed. Subsequently, when the surgeon was adjusting the diameter of band on the main pulmonary artery during PAB, TEE monitoring revealed a residual PDA shunt on color Doppler imaging. There was a discrete mosaic jet moving from the descending aorta toward the pulmonary artery (Fig. 1), suggesting incomplete PDA ligation. The surgeon consequently applied a hemoclip to the PDA, and the shunt was confirmed to have disappeared on TEE. The main pulmonary artery was finally strangulated using a 24-mm band, resulting in a peak pressure gradient of 41.9 mmHg at the PAB site when the systemic arterial pressure was 74/45 mmHg. With no residual PDA flow thereafter, the patient successfully underwent ventricular septal defect closure and pulmonary arterioplasty at the age of 17 months.