Comparison of the properties of spot and ring electrodes in transesophageal cardiac pacing

: The authors compare diagnostic oesophageal pacing of the left atrium by a ring and spot electrode using poles with an area of 20 mm2 oriented towards the left atrium. The examination was made in 15 volunteers, aged 37 +/- 5 years (range 28-43 years). In different depths of the oesophagus the threshold of stimulation was assessed (PS) and the threshold of perception of stimulation (PV) of the left atrium. At each of the examined levels the amplitude of waves A and V was determined as well as the A/V ratio. The change from a ring to a spot electrode reduces the PS from 12.2 +/- 2:3 (8.0-15.0 O) mA to 8.0 +/- 1.3 (6.0-10.0) mA. When the spot electrode is used, the difference between PS and PV is markedly reduced; one third of the examined subjects can be stimulated without subjective perception. The amplitude of the A wave recorded by means of the spot electrode was not reduced, as compared with the ring electrode and the optimal A/V ratio above 2:1 was recorded by the spot electrode on a longer section of the oesophagus. Evidence was also provided that the lowest PS is 3-4 cm beneath the site of recording of the maximum amplitude of wave A.