The optimal oesophageal pacing technique - The importance of body position, interelectrode spacing, electrode surface area, pacing waveform and intra-oesophageal local anaesthesia

In order to improve the technique of transoesophageal atrial stimulation (T AS), the effects of body position, interelectrode spacing and electrode sur face area on pacing threshold were assessed in two substudies. The effects of intra-oesophageal local anaesthesia and of two different pacing wave con figurations on pacing threshold and discomfort were also assessed. Substudy I comprised 16 subjects (3 patients with a history of paroxysmal supravent ricular tachycardia and 13 healthy volunteers) and substudy II comprised 16 healthy volunteers. TAS was performed using a hexapolar luminal prototype oesophageal electrode catheter. Ln substudy I bipolar pacing was performed in the semi-supine and left decubitus body positions for different pulse du rations (20, 10, 6 and 2 ms), interelectrode pole distances (10 to 24 mm) a nd electrode pole surface areas (0.22 to 0.66 cm(2)). In substudy Ii TAS wa s performed with square wave and triangular waveform pulses after intra-oes ophageal saline and lidocaine 20 mg/ml. These solutions were given in rando m order. Neither the interelectrode distance nor electrode surface areas ha d any significant influence on pacing thresholds. Stimulation thresholds we re not affected by body position. Intraoesophageal lidocaine did not affect the discomfort experienced. Peak pacing thresholds using a triangular wave form were significantly higher than thresholds using a square waveform (p < 0.001). The optimal pacing technique for TAS remains to be defined. The TA S-induced pain is probably not generated from the oesophageal mucous membra ne. There is a significant difference in pacing thresholds between triangul ar and square waveforms.