ARRHYTHMIAS AND CONDUCTION DISTURBANCES Transesophageal Pacing for Prognostic Evaluation of Preexcitation Syndrome and Assessment of Protective Therapy GIUSEPPE CRITELLI, MD, GINO GRASSI, PhD, FRANCESCO PERTICONE, MD, FERNANDO COLTORTI, MD, VITTORIO MONDA, MD, and MARIO CONDORELLI, MD An esophageal lead was used to perform decre- mental atrial pacing and elective induction of atrial fibrillation (AF) in 5 patients with the Wolff-Parkin- son-White (W-P-W) syndrome before and after amiodarone therapy. In the control state, 1.'1 atrio- ventricular (AV) conduction over the accessory pathway ranged from 220 to 260 ms (mean 232). The shortest R-R interval during AF ranged from 190 to 210 ms (mean 198). The ventricular rate ranged from 175 to 212 beats/min (mean 196). After ami- odarone therapy, the shortest cycle length with 1:1 AV conduction increased in all patients, ranging from 290 to 540 ms (mean 370); during AF, no preexcited beat was present in 2 patients, whereas the minimal preexcited R-R interval in the remaining 3 was 290, 240, and 370 ms, respectively. The ventricular re- sponse during AF decreased in all patients. Thus, esophageal pacing is a useful method for identifying patients at risk with the W-P-W syndrome and for assessing appropriate management in individual patients. Amiodarone provides protection against life-threatening arrhythmias in these patients. The prognosis of preexcitation syndrome due to an ac- cessory AV pathway (W-P-W syndrome) is considered with less optimism than it was in the past, because life-threatening arrhythmias and sudden death have been reported with it. 1-6 The determinant of risk in the preexcitation syndrome is a very short anterograde ef- fective refractory period of the accessory pathway, which can be responsible for a rapid ventricular re- sponse when atrial flutter or AF develops. 5,7-1° In fact, previous studies found a correlation between the du- ration of the anterograde effective refractory period of the accessory pathway and the ventricular response during AF. 11qa To evaluate the ventricular response during faster atrial rates and to assess protective drug regimen in patients with the W-P-W syndrome at risk, an esophageal lead was used to perform decremental atrial pacing and elective induction of AF. From the Istituto di Patologia Medic& II Facolt& di Medicina e Chirurgia, Universit& di Napoli, Naples, Italy. This study was supported in part by Grant 80,02493,11 from the National Research Council (CNR), Rome, Italy. Manuscript received July 14, 1982, accepted September 29, 1982. Address for reprints: Prof. Giuseppe CrRelli, Istituto di Patologia Medica, II Policlinico, Via Sergio Pansini, 5, 80131, Napoli, Italy. Methods Patients: The study group consisted of 4 male patients and 1 female patient, aged 18 to 38 years (mean 27), selected from 52 consecutive patients with the W-P-W syndrome. One pa- tient had been resuscitated from VF, 1 had a history of tachycardia, and 3 had familial W-P-W syndrome with a history of sudden death in 2 other family members. All pa- tients had previously undergone endocavitary electrode catheter study for electrophysiologic evaluation of the W-P-W syndrome. Four patients had multiple accessory pathways; in addition, enhanced conduction of the AV node was present in 3 and a Mahaim fiber of the fasciculoventricular variety in l. Procedure: Studies were performed in the postabsorptive, nonsedated state. A bipolar permanent transvenous pacing lead with a 29 mm interelectrode distance (Medtronic Coro- nary Sinus Permanent Pacing Lead model 6992) was passed through the nares into the distal esophagus with the patient supine. The lead was secured where unipolar atrial electro- grams showed the greatest amplitude and the most rapid deflection on the proximal electrode; this electrode was then designated as the cathodal (negative) pacing terminal. The unipolar tracings were filtered at 0.1 to 1 kHz. The pulse du- ration of the external generator ranged from 7 to 10 ms, and the current strength required for a stable capture ranged from 513