Thresholds for transesophageal atrial pacing.

To determine the thresholds for transesophageal atrial capture, as well as factors that may influence the thresholds, we measured the minimal current and pulse width required to pace the atria through transesophageal bipolar lead systems in 12 patients, ranging in age from 1 day to 19 years, during 19 episodes of reentrant supraventricular tachycardia. Depending on the patients' age and size several electrode catheters were used. The protocol called for 1-msec step-wise increments in pulse width. At each pulse width the current was increased by 1 mamp until capture was achieved. The mean minimal pulse width and mean minimal current required for capture were 5.8 msec and 13.6 mamp, respectively. Atrial capture was achieved in 75% of attempts at a pulse width and current equal to or less than 6.5 msec and 17.5 mamp, respectively. No correlation between current and pulse width on the one hand and age, height, weight, or body surface area on the other was detected. Likewise neither electrode type nor existence of structural heart disease influenced the threshold required for capture. We conclude that atrial capture can be readily achieved through transesophageal electrodes and is not influenced by the subject's age or size.