A standard bipolar transesophageal catheter was inserted through the mouth and pacing was performed at interelectrode spacing of 40 mm and pulse duration of 10 ms.
It was electrically connected to the distal electrode of the esophageal catheter and the pacing threshold was determined again.
In clinical practice, transesophageal cardiac pacing usually causes patients discomfort or pain.
The lead set, exhibiting minimum pacing threshold, was determined (Fig.
1) 2 ms at the lead, exhibiting the minimum atrial pacing threshold, determined in phase I of the study;
2) 2 ms at the proximal lead, adjacent to the lead exhibiting the minimum atrial pacing threshold, determined in phase I of the study;
4) 2 ms at the distal lead, adjacent to the lead, exhibiting the minimum atrial pacing threshold, determined in phase I of the study;
Again, the pacing current was gradually increased until stable atrial capture was confirmed by surface ECG.
Stimulation points 1 cm to distal or proximal to optimal position also assure acceptable pacing thresholds.
By selecting lead configuration according to the individual patient, pacing current threshold was reduced in 8 of 15 patients by 9 to 55%, 20% on average.
Using a external chest electrode, connected in parallel with distal esophageal electrode, allowed effective atrial capture in more than 80% of patients at pacing pulse current 13 mA or less, while 19 mA was required for 100% capture (Fig.
In 5 patients, a somewhat higher (from +7 to +13%) pacing threshold was recorded.
There are two main sources of discomfort in the TOE electrophysiological study--the initial introduction of the pacing catheter into the esophagus and the burning sensation caused by the pacing current.