Positioning the pacing esophageal stethoscope for transesophageal atrial pacing without P-wave recording: implications for transesophageal ventricular pacing.

This study determined guidelines for positioning a new pacing esophageal stethoscope (PES) used for transesophageal atrial pacing (TEAP) without having to record esophageal P waves. In 44 patients with heights ranging from 142 cm (4'8") to 193 cm (6'4"), the PES was inserted to a depth of insertion (DOI) of 43 cm. As the PES was withdrawn, TEAP thresholds were determined at every DOI in 1-cm intervals between 43 and 25 cm DOI inclusive. TEAP was accomplished in all 44 patients. The minimum TEAP threshold (mean +/- SD 10.8 +/- 4.0 mA) was < or = 17 mA in 43 of 44 patients (98%). Except for one patient, TEAP could be accomplished over a 9- to 19-cm (mean +/- SD, 13.7 +/- 2.8 cm) wide range of DOI. Unintentional transesophageal ventricular pacing (TEVP) occurred in 15 of 44 (34%) of patients. TEVP occurred over a 1- to 7-cm (mean +/- SD, 3.7 +/- 1.7 cm) wide range of DOI; the minimum TEVP threshold averaged 30.4 +/- 6.4 mA. TEAP was consistently accomplished at DOIs more proximal than where TEVP could occur and with lower currents than that required for TEVP. An insertion depth, in centimeters, equal to half of the patient's height, in inches, produced successful TEAP in all 44 patients; the minimum TEAP threshold occurred on average at a DOI 2.6 cm more proximal. Asynchronous TEVP can be avoided by using lower currents at shallow DOIs.