Right atrial substrate properties associated with age in patients with typical atrial flutter Jin-Long Huang, MD, PhD,* †‡ Ching-Tai Tai, MD, †‡ Yenn-Jiang Lin, MD, †‡ Kwo-Chang Ueng, MD, PhD, § Bien-Hsien Huang, MD, †‡ Kun-Tai Lee, MD, †‡ Satoshi Higa, MD, # Yoga Yuniadi, MD, †‡ Shih-Lin Chang, MD, †‡ Li-Wei Lo, MD, †‡ Wanwarang Wongcharoen, MD, †‡ Yu-Feng Hu, MD, †‡ Pi-Chang Lee, MD, †‡ Ta-Chuan Tuan, MD, †‡ Chih-Tai Ting, MD, PhD,* ‡ Shih-Ann Chen, MD †‡ From the *Heart Failure Division, Cardiovascular Center, Taichung Veterans General Hospital, † Division of Cardiology, Department of Medicine, Taipei Veterans General Hospital, ‡ Institute of Clinical Medicine, and Cardiovascular Research Institute, National Yang-Ming University, Taipei, Taiwan, and § Cardiovascular Research Group, Institute of Medicine, Division of Cardiology, Chung-Shan Medical University Hospital, Taiwan, # Second Department of Internal Medicine, Faculty of Medicine, University of Ryukyus, Okinawa, Japan. BACKGROUND Data detailing the age-related difference in the atrial substrate for formation of typical atrial flutter (AFL) are sparse. OBJECTIVE The purpose of this study was to characterize the difference in the right atrial substrate related to aging using noncontact mapping of the right atrium. METHODS A total of 54 patients (23 young [60 years; 45  12 years] and 31 old [60 years; 74  6 years]) with typical AFL who underwent three-dimensional noncontact mapping of typical AFL were enrolled in the study. The atrial substrate was characterized according to (1) regional wavefront activation mapping, (2) re- gional conduction velocity, and (3) regional voltage distribution by dynamic substrate mapping. RESULTS During activation mapping of the crista terminalis, two activation patterns were observed: (1) around the upper end of the crista terminalis (67%) and (2) through a gap in the crista terminalis. The presence of a crista terminalis gap was associated with a high incidence of induced atypical AFL/atrial fibrillation (P .001). The conduction velocities of the medial cavotricuspid isthmus were slower in the old group than in the young group. In regional activation mapping of the AFL, the location of the slowest conduction shifted from the lateral cavotricuspid isthmus (71%) in the young group to the medial cavotricuspid isthmus (40%) in the old group. More cases with a low-voltage zone (30% peak negative voltage) extending to the medial side of the cavotricuspid isthmus occurred in the old group than in the young group (55% vs 17%, P  .012). CONCLUSION The atrial substrate responsible for formation of typical AFL differed between young and old patient groups. KEYWORDS Typical atrial flutter; Noncontact mapping; Atrial sub- strate; Age; Cavotricuspid isthmus (Heart Rhythm 2008;5:1144 –1151) © 2008 Heart Rhythm Society. All rights reserved. Introduction Typical atrial flutter (AFL) has been well demonstrated as a macroreentrant circuit confined to the right atrium (RA). Maintenance of the AFL circuit may rely on the slow conduction zone in the cavotricuspid isthmus (CTI) 1–14 or in other regions. 15–17 Noncontact three-di- mensional mapping of AFL could provide detailed infor- mation on regional conduction properties and the atrial substrate. A population-based investigation of AFL re- vealed that the age-specific incidence of AFL increases exponentially with age over 60 years. 18 Data detailing the age-related differences that occur in the atrial substrate related to formation of typical AFL are sparse. Animal studies on aging-related changes in the atrium have dem- onstrated the presence of interstitial fibrosis associated with variable conduction slowing. 19,20 Detailed human electrophysiologic studies describing the nature of the age-related atrial remodeling are lacking. This laboratory has demonstrated that high-density unipolar voltage mapping can offer a unique electrophysi- ologic description of the atrial substrate in patients with atrial arrhythmias. 21–31 However, the difference in the RA substrate that occurs with age in patients with typical AFL remains unclear. The aim of the present study was to char- acterize the atrial substrate and conduction properties be- tween young and old patient groups. Supported in part by Grants TCVGH-953107C, -963107C, and -973106C from Taichung Veterans General Hospital and Grants CI 96-17, CI-95-14, and CI-94-11 from Yen Tjing Lin Medical Foundation, Taiwan, Republic of China. Address reprint requests and correspondence: Dr. Jin-Long Huang, Cardiovascular Center, Taichung Veterans General Hos- pital, 160, Section 3, Chung-Kang Road, Taichung City, Taiwan. E-mail address: golden@vghtc.gov.tw. (Received March 25, 2008; accepted May 9, 2008.) 1547-5271/$ -see front matter © 2008 Heart Rhythm Society. All rights reserved. doi:10.1016/j.hrthm.2008.05.009