950 June 2001 PACE, Vol. 24 Introduction The management of recurrent intraatrial reen- trant tachycardia (IART) after surgical repair of congenital heart disease continues to challenge clinicians. A high incidence of this arrhythmia has been noted in long-term follow-up, particu- larly in patients after intraatrial surgeries such as the Mustard or Senning procedure for palliation of d-transposition of the great arteries and the Fontan procedure for single ventricle physiology. 1–4 Su- ture lines, surgical cannulation, and scarring of atrial tissue provide areas of slow conduction and unidirectional block capable of supporting atrial reentrant tachycardia. 5 The complexity of the components that formed this type of reentrant circuit makes it distinct from the adult classic type I atrial flutter that evolves around uniform anatomic obstacles such as the inferior venae cavae. Diagnosis of IART poses an additional chal- lenge as the electrocardiographic (ECG) morphol- ogy and rate can be variable and are often different from the sawtooth pattern and the typical rates of type I atrial flutter. IART may coexist with sinus bradycardia, 1 and often pacemaker implantation is required. Management of IART is difficult and requires acute termination of tachycardia recur- rences and chronic antiarrhythmic drug therapy. Techniques for acute termination of IART in- clude transcatheter or transesophageal atrial over- drive pacing or direct current cardioversion. 6,7 These procedures are moderately invasive and re- quire the use of sedation or general anesthesia when performed in young children. Overdrive pacing termination of reentrant tachycardia relies on the ability of the pacing impulses to penetrate the excitable gap within the reentrant circuit. Suc- cessful conversion depends on the stimulation site and on achieving a critical pacing rate and du- ration. 8–10 With the use of atrial-based pacing therapy for these patients, the pacemaker system offers an- other approach by which atrial overdrive pacing can be accomplished noninvasively under a con- Clinical Use of Permanent Pacemaker for Conversion of Intraatrial Reentry Tachycardia in Children CHRISTINE C. CHIU, BRIAN W. MCCRINDLE, ROBERT M. HAMILTON, JEAN E. GRIFFITHS, and ROBERT M. GOW From The Division of Cardiology, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada CHIU, C.C., ET AL.: Clinical Use of Permanent Pacemaker for Conversion of Intraatrial Reentry Tachycar- dia in Children. The use of the implanted atrial-based pacemaker to overdrive postsurgical intraatrial reen- try tachycardia (IART) was evaluated in a large group of pediatric patients over a 14-year study period. The authors sought to determine the feasibility of this noninvasive technique in the management of this spe- cialized population and to determine factors associated with successful conversion. They examined 128 manual overdrive attempts performed on 22 consecutive patients. There were 10 patients with post-Fontan repair, 7 with post-Mustard/Senning procedure, and 5 with miscellaneous lesion types. The number of IART episodes for overdrive pacing per patient ranged from 1 to 15. The first overdrive pacing attempt was successful in 63% (14/22) of the patients. The mean IART cycle length was 278 6 59 ms. The mean pacing rate for effective conversion of IART was 66 6 10% faster than the IART rate. By controlling for repeated measures for individual patients, three factors were found to be independently associated with a success- ful outcome: (1) lesion type other than Fontan surgery (P 5 0.007), (2) lack of acceleration of IART with the overdrive attempt (P , 0.001), and (3) patient use of amiodarone with attempt (P 5 0.005). There were three procedural complications: two inadvertent overdrive pacing episodes, and one episode of acceleration of IART cycle length and conduction resulting in need for cardioversion. Manual pacemaker overdrive con- version of IART is a useful adjunct in the management of postsurgical IART in the pediatric population and should be considered as an initial treatment option. (PACE 2001; 24:950–956) overdrive pacing, pacemaker, atrial flutter, intraatrial reentry tachycardia, children Address for reprints: Robert Gow, MBBS, Division of Cardiol- ogy, Children’s Hospital of Eastern Ontario, 401 Smythe Rd., Ottawa, Ontario, K1H 8L1, Canada. Fax: (613) 738-4835; e- mail: rgow6cheo.on.ca Received June 12, 2000; revised October 30, 2000; accepted November 16, 2000. Reprinted with permission from JOURNAL OF PACING AND CLINICAL ELECTROPHYSIOLOGY , Volume 24, No. 6, June 2001 Copyright © 2000 by Futura Publishing Company, Inc., Armonk, NY 10504-0418.