Hesselvik JF, Ortega RA. Boston University Medical Center. J Cardiothorac Vasc Anesth 1998 Jun;12(3):281-3. OBJECTIVES: To measure the effect of inserting a transesophageal echocardiography (TEE) probe on the pacing threshold of a previously inserted transesophageal pacing stethoscope, and to examine whether an indwelling pacing stethoscope influences the feasibility and image quality of a TEE examination. DESIGN: Prospective, open study using each patient as his/her own control. SETTING: Cardiac operating room of an academic medical center. PARTICIPANTS: Twenty adult patients in sinus rhythm and anesthetized for cardiac surgery. INTERVENTIONS: After induction of anesthesia and endotracheal intubation, a pacing stethoscope was inserted into the esophagus. A 5-MHz TEE probe was inserted to the four-chamber-view position. A full echocardiographic examination was performed, noting image quality, ease of probe manipulation, and loss of pacing. The pacing stethoscope was removed, and image quality assessed again. MEASUREMENTS AND MAIN RESULTS: The initial mean pacing threshold +/- 1 standard deviation (SD) was 19 +/- 8 mA (range, 10 to 37 mA). After placement of the echocardiography probe, the mean threshold had increased to 24 +/- 8 mA (range, 11 to 40 mA; p < 0.01). Loss of pacing with probe manipulation was noted in 15 of 20 patients (transient in 10 patients, permanent in 5 patients). Problems manipulating the probe because of sticking to the pacing stethoscope were noted in 10 of 20 patients. Poor image quality, resolving after stethoscope removal, was seen in two patients. CONCLUSION: Placement of a TEE probe results in a modest increase of the transesophageal pacing threshold. An indwelling pacing stethoscope frequently interferes with the ability to perform a full echocardiographic examination, and probe manipulation commonly causes loss of pacing.