Nishimura M, Katoh T, Hanai S, Watanabe Y. Am J Cardiol 1986;57(10):791-6. The optimal mode of transesophageal atrial pacing was determined by clinical electrophysiologic studies in 15 healthy adult volunteers. The point at which the unipolar atrial electrogram was biphasic and largest in amplitude (35.4 +/- 1.6 cm from the incisors) was considered the best stimulation site for atrial pacing. The stimulation threshold on bipolar pacing (using the proximal pole as cathode and the distal pole as anode) at this site was 27 +/- 7 mA, which was significantly lower (p < 0.001, n = 10) than that on unipolar cathodal stimulation (41 +/- 8 mA). Although the stimulation threshold tended to be higher with a No. 10Fr electrode catheter (30 +/- 5 mA) than with a No. 6Fr catheter (27 +/- 7 mA), the difference was statistically insignificant (n = 9). When the interpolar distance in bipolar stimulation was varied in 5 steps from 12 to 80 mm, the threshold was lowest at the distance of 24 mm. Of the 10 pulse durations tested, ranging from 0.25 to 128 ms, 8 ms appeared most desirable in minimizing the total amount of current and chest discomfort accompanying the pacing. With the optimal site, interpolar distance and pulse duration, transesophageal atrial pacing was successfully performed in all patients, without producing significant complications such as chest pain. Transesophageal atrial pacing is noninvasive, technically simple and efficient, and may be valuable in the diagnosis and treatment of various cardiac arrhythmias.