Transesophageal pacing : a versatile diagnostic and therapeutic tool

Transesophageal pacing and recording is done using specialized or non specialized catheters. There are two different lead types: 1) the pill electrode, connected to a flexible wire, that the patient swallows with water. This pill electrode necessitates patient collaboration. 2) a flexible catheter that can even be used in comatose or intubated patients. The pacing lead, in our cases a bipolar flexible catheter, is introduced into the oesophagus via the nares after local nose anesthesia with xylocaine spray. Sometimes throat anesthesia with the same spray is also performed. Xylocaine gel is used to lubricate the lead and the lead is introduced with guidewires in it in order to increase its stiffness. It is positioned into the oesophagus in order to record the posterior paraseptal atrial electrogram. There is a relationship between the site of maximal atrial amplitude and the lowest atrial pacing threshold. The optimal atrial pacing site is usually found around 40 cm from the nares. Bipolar or unipolar recordings can be made. The strengh-duration curve of esophageal pacing is different than that of endocardial pacing. The lowest thresholds can be reached at pulse widths between 10 and 20 msec. Thresholds at these pulse widths are usually situated between 5 and 15 mA 2. So transesophageal pacing necessitates a specific pacing device and external pacemakers cannot be used for that purpose. Commercially available transesophageal pacing systems are usually restricted to burst pacing only. They frequently have an input where one can connect a programmable stimulator that will trigger esophageal pacing enabling the delivery of extrastimuli. The tracings shown were all obtained in our center using the following equipment: a Medtronic 6992A bipolar pacing lead (Fig.1) initially designed to pace the coronary sinus on a permanent basis, a dedicated A.P.I. Electronique Oesostim 2 transesophageal stimulator able to provide a maximal pulse width of 22 ms and a maximal current intensity of 44 mA, an implantable programmable pacemaker Medtronic Kappa KDR 700 that is connected to the ‘synchronisation input’ of the esophageal stimulator in order to deliver a maximum of 4 programmable extrabeats using the non invasive