SUMMARYTransesophageal atrial pacing study was used to document arrhythmias in 67 infants and children age 2 months to 16 years (mean, 8.3 years), who had palpitations or symptoms suggesting tachyarrhythmias but had no electrocardiographic documentation of cardiac dysrhythmias. The transesophageal pacing and medical records were reviewed retrospectively.In 47 of 67 (70%) of the infants and children with suspected tachyarrhythmias, transesophageal atrial pacing induced various tachycardias, which may be the cause of symptoms. In 10 of 67 patients, tachycardia was induced during infusion of isoproterenol. During the study, tachycardia was initiated in 14 of 15 patients less than < 6 years-old and in 33 of 52 patients ≥ 6 years-old (P < 0.05). Of these induced tachycardias, 25 of 47 were atrioventricular reciprocating tachycardia, 16 atrioventricular nodal reentrant tachycardia, and 6 idiopathic left ventricular tachycardia. Both transesophageal study and invasive electrophysiologic study were performed in 10 patients. The mechanisms of tachycardia in the invasive study and transesophageal study were identical except for one patient.In conclusion, transesophageal atrial pacing and recording was less invasive, safe and useful for documenting arrhythmias in infants and children who had symptoms suggesting tachyarrhythmias, especially in patients < 6 years of age. Evaluation of the mechanism of induced tachycardia provided useful information regarding the prognosis and therapeutic options in infants and children. (Jpn Heart J 2004; 45: 63-72)