right atrium is accepted by the investigator, changes cannot be made afterward in the present version. At times, this may not be advantageous, because a more accurate representation of the area of interest (atrial focus) could become necessary during the study. A potential advantage of the non-contact mapping system may be the capability to localize and ablate tachycardias that are unstable or short lasting. Al- though this study shows feasibility in diagnosing and ablating these tachycardias, the number of patients included in this study is low. The potential advantage of the non-contact mapping system over conventional catheter techniques needs to be shown in a larger randomized study. Use of the new high-resolution non-contact mapping system in patients with focal right atrial tachycardias is safe and effective in identifying and ablating the tachycardia origin. With this system, diagnosis and ablation procedures in patients with unstable tachycardias is facilitated. 1. 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Circulation 1993;88:578 –587. 9. Kadish AH, Morady F. The response of paroxysmal supraventricular tachy- cardia to overdrive atrial and ventricular pacing: can it help determine the tachycardia mechanism? J Cardiovasc Electrophysiol 1993;4:239 –252. 10. Schmitt C, Zrenner B, Schneider M, Karch M, Ndrepepa G, Deisenhofer I, Weyerbrock S, Schreieck J, Schomig A. Clinical experience with a novel mul- tielectrode basket catheter in right atrial tachycardias. Circulation 1999;99:2414 – 2422. 11. Schilling RJ, Peters NS, Davies DW. Feasibility of a noncontact catheter for endocardial mapping of human ventricular tachycardia. Circulation 1999;99: 2543–2552. 12. Gepstein L, Hayam G, Ben-Haim SA. A novel method for nonfluoroscopic catheter-based electroanatomical mapping of the heart. In vitro and in vivo accuracy results. Circulation 1997;95:1611–1622. 13. Schilling RJ, Peters NS, Davies DW. Simultaneous endocardial mapping in the human left ventricle using a noncontact catheter: comparison of contact and reconstructed electrograms during sinus rhythm. Circulation 1998;98:887– 898. 14. Schilling RJ, Davies DW, Peters NS. Characteristics of sinus rhythm elec- trograms at sites of ablation of ventricular tachycardia relative to all other sites: a noncontact mapping study of the entire left ventricle. J Cardiovasc Electro- physiol 1998;9:921–933. 15. Tracy CM, Swartz JF, Fletcher RD, Hoops HG, Solomon AJ, Karasik PE, Mukherjee D. Radiofrequency catheter ablation of ectopic atrial tachycardia using paced activation sequence mapping. J Am Coll Cardiol 1993;21:910 –917. Exercise Capacity After Repair of Tetralogy of Fallot in Infancy Anji T. Yetman, MD, Kyong-Jin Lee, MD, Robert Hamilton, MD, William R. Morrow, MD, and Brian W. McCrindle, MD, MPH T he long-term outcome of children after complete repair of tetralogy of Fallot (ToF) has been well described. 1,2 Impairment in exercise tolerance has been frequently reported 3–6 and speculated to be due to a number of causes including residual right ventric- ular (RV) outflow tract obstruction, 7 branch pulmo- nary artery stenoses, 6 pulmonary insufficiency, 3,5,7–9 chronotropic incompetence, 4 and pulmonary patholo- gy. 10 –12 Published reports have focused on children with an older age at repair. 1–5,7,10 –14 Repair in infancy frequently necessitates placement of a transannular patch, and raises concerns as to the long-term effect of chronic pulmonary insufficiency in those repaired at an early age. Although there is a growing body of published data on those repaired in early childhood, 6,8 the long-term impact on aerobic capacity in those repaired during infancy remains unknown. We sought to assess long-term outcome of children with ToF repaired in infancy (age 18 months), with an em- phasis on cardiopulmonary exercise performance, and to identify any potential factors associated with im- paired aerobic capacity. In addition, we sought to compare exercise performance in children repaired in infancy with that in similar children who were re- paired at an older age. ••• Cardiopulmonary stress testing and echocardiogra- phy were performed in 74 patients who underwent repair of ToF between 1982 and 1992 at 1 of 2 tertiary cardiac centers. Within this study population, a sub- group of 22 patients repaired at an age 18 months was identified and served as the focus of this study, with the remaining patients who were repaired at a later age serving as a comparison group. The period of 1982 to 1992 was chosen for review, because there From the Department of Pediatrics, Divisions of Cardiology, Arkansas Children’s Hospital, Little Rock, Arkansas; and The Hospital for Sick Children, Toronto, Ontario, Canada. Dr. Yetman’s address is: Depart- ment of Cardiology, Arkansas Children’s Hospital, 800 Marshall Street, Little Rock, Arkansas 72202. E-mail: yetmananjit@ exchange.uams.edu. Manuscript received September 19, 2000; re- vised manuscript received and accepted November 1, 2000. 1021 ©2001 by Excerpta Medica, Inc. All rights reserved. 0002-9149/01/$–see front matter The American Journal of Cardiology Vol. 87 April 15, 2001 PII S0002-9149(01)01443-6