A GASTROESOPHAGEAL ELECTRODE FOR ATRIAL AND VENTRICULAR PACING

Temporary transvenous cardiac pacing requires technical expertise and access to fluoroscopy. We have developed a gastroesophageal electrode capable of atrial and ventricular pacing. The flexible polythene gastr oesophageal electrode is passed into the stomach under light sedation. Five ring electrodes, now positioned in the lower esophagus, are used for atrial pacing. A point source (cathode on the distal tip of the e lectrode, now positioned in the gastric fundus, is used for ventricula r pacing. Two configurations of atrial and ventricular pacing were com pared: unipolar and bipolar. During unipolar ventricular pacing the in different electrode (anode) was a high impedance chest pad. For bipola r ventricular pacing the indifferent electrode was a ring electrode pl aced 2 cm proximal to the tip. Unipolar atrial pacing nas performed wi th 1 of 5 proximal ring electrodes acting as cathode (''cathodic'') or as anode (''anodic'') in conjunction with a chest pad. Bipolar atrial pacing was performed using combinations of 2 of 5 ring electrodes. At rial capture was obtained in all 55 subjects attempted. When all elect rode combinations were compared, atrial capture was significantly more frequent using the bipolar approach (153/210 bipolar, 65/210 unipolar ; t = 7.37, P < 0.001). For unipolar atrial pacing cathodic stimulatio n (from esophagus) was more successful than anodic stimulation (cathod ic 62/105, anodic 20/105; t = 5.81, P < 0.001). In 43 subjects attempt ed unipolar ventricular pacing resulted in a higher frequency of captu re than the bipolar approach (unipolar 41/43 (95.3%), bipolar 19/43 (4 4.2%); P < 0.001). In conclusion, atrial pacing was optimal using pair s of ring electrodes (''bipolar'') while ventricular pacing was optima l using the distal electrode tip (cathode) in conjunction with a chest pad electrode (''unipolar''). This gastroesophageal electrode may be useful in the emergency management of acute bradyarrhythmias and for e lective electrophysiological studies.