Pattison CZ; Atlee JL 3d; Mathews EL; Buljubasic N; Entress JJ. Medical College of Wisconsin. Anesthesiology, May 1991, 74(5) p854-9. Transesophageal atrial pacing (TAP) with the use of standard, thermistor-equipped, esophageal stethoscopes, modified for pacing by incorporation of a 4-French, bipolar TAP probe (pacing esophageal stethoscope [PES]), was evaluated in 100 adult patients under general anesthesia. A commercially available TAP pulse generator supplied 10-ms pulses with current variable between 0 and 40 mA. Pacing distances (in centimeters) were measured from the infraalveolar ridge to midway between PES electrodes (1.5-cm interelectrode distance). Pacing thresholds (milliamperes) were measured at the point of a maximum-amplitude P-wave (PMAX) in the bipolar esophageal electrogram and points 1 cm proximal or 1, 2, or 3 cm distal to PMAX. TAP (70-100 beats per min) was used for sinus bradycardia less than or equal to 60 beats per min (36 patients) or atrioventricular (AV) junctional rhythm (2 patients) and blood pressure changes with TAP documented. In male patients (n = 49), PMAX was 32.7 +/- 0.3 cm (mean +/- SE) and minimum pacing threshold 5.1 +/- 0.4 mA (range, 1-13 mA) at 33.6 +/- 0.3 cm (range, 30-37 cm). In female patients (n = 51), PMAX was 30.4 +/- 0.4 cm and minimum pacing threshold 4.4 +/- 0.4 mA (range, 2-14 mA) at 31.1 +/- 0.4 cm (range, 26-40 cm). TAP produced an average 13-16 mmHg increase in systolic, diastolic, or mean arterial pressure in patients with sinus bradycardia or AV junctional rhythm. There were no subjective patient complaints (epigastric discomfort, dysphagia) that could be attributed to TAP; objective evaluation (esophagoscopy) was not performed. It is concluded that TAP is widely applicable to anesthetized adults; low TAP thresholds can be obtained by first determining Pmax and positioning the PES electrode 1 cm or less distal to Pmax; and TAP can be used to increase blood pressure in patients with sinus bradycardia or AV junctional rhythm.