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1 MAIN TOPIC REVIEWS Young-Keun On, MD, PhD Division of Cardiology, Department of Medicine Cardiac & Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea Catheter ablation for tachycardia-bradycardia syndrome ABSTRACT Sinus node (SAN) dysfunction is frequently associated with atrial fibrillation (AF), and can lead to syncopal attacks after AF termination, a condition forming the basis of the tachycardia-bradycardia syndrome. Although abnormalities of SAN structure have been noted in patients with AF, there is increasing evidence of a reversible component related to SAN remodeling caused by rapid atrial tachyarrhythmias. It has been demonstrated that when AF patients show prolonged sinus pauses on AF termination, successful AF ablation is followed by a marked recovery in SAN function indices. In animal models, atrial tachyarrhythmia downregulates SAN HCN2/4 and mink subunit expression, along with the corresponding currents If and IKs. Tachycardia-induced remodeling of SAN ion channel expression, particularly for the pacemaker subunit If, may contribute to the clinically significant association between SAN dysfunction and supraventricular tachyarrhythmias. SAN dysfunction in AF is also associated with calcium clock malfunctioning, characterized by unresponsiveness to isoproterenol caffeine and the down-regulation of type 2 ryanodine recepter (RYR2) in SAN. Therefore sinus node dysfunction caused by atrial tachyarrhythmias could be reversed by curative ablation of AF, thus avoiding the need for pacemaker implantation. Radiofrequency cathether ablation should be an opinion of the treatment for the tachycardia-bradycardia syndrome. Key words: tachycardia-bradycardia syndrome atrial fibrillation ablation Received: May 28, 2010 Revision Received: August 16, 2010 Accepted: Correspondence: Young-Keun On, MD, PhD. Division of Cardiology, Department of Medicine Cardiac & Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul , Korea Tel: , Fax: VOL.11 NO.3 23

2 MAIN TOPIC REVIEWS Figure 1. Twenty six old lady complained of palpitation, dizziness and presyncope. The electrocardiogram shows irregular heart rhythm and rapid heart beats. Figure 2. Tachycardia-bradycardia syndrome. The electrocardiogram shows rapid heart beats and abrupt termination of tachycardia followed by sinus pause. 24 Journal of Cardiac Arrhythmia

3 MAIN TOPIC REVIEWS Figure 3. The atrial fibrillation converted to atrial flutter during the ablation of left pulmonary vein antrum. Figure 4. The atrial flutter was terminated during the ablation of cavotricuspid isthmus and followed by pause and sinus rhythm. VOL.11 NO.3 25

4 MAIN TOPIC REVIEWS Figure 5. Intracardiac electrogram shows normal sinus rhythm after the ablation. Figure 6. After the catheter ablation of atrial fibrillation the patient didn Øt complain of palpitation and dizziness and the electrocardiogram shows normal sinus rhythm. 26 Journal of Cardiac Arrhythmia

5 MAIN TOPIC REVIEWS VOL.11 NO.3 27

6 MAIN TOPIC REVIEWS References 1. Allessie M, Ausma J, Schotten U. Electrical, contractile and structural remodeling during atrial fibrillation. Cardiovasc Res. 2002;54: Thery C, Gosselin B, Lekieffre J, Warembourg H. Pathology of sinoatrial node: correlations with electrocardiographic findings in 111 patients. Am Heart J. 1977;93: Elvan A, Wylie K, Zipes DP. Pacing-induced chronic atrial fibrillation impairs sinus node function in dogs: electrophysiological remodeling. Circulation. 1996;94: Hocini M, Sanders P, Deisenhofer I, Jais P, Hsu LF, Scavee C, Weerasoriya R, Raybaud F, Macle L, Shah DC, Garrigue S, Metayer PL, Clementy J, Haissaguerre M. Reverse remodeling of sinus node function after catheter ablation of atrial fibrillation in patients with prolonged sinus pauses. Circulation. 2003;108: Yeh YJ, Burstein B, Qi XY, Sakabe M, Chartier D, Comtois P, Wang Z, Kuo CT, Nattel S. Funny current downregulation and sinus node dysfunction associated with atrial tachyarrhythmia-a molecular basis for tachycardia-bradycardia syndrome. Circulation. 2009;119: Joung B, Lin SF, Chen Z, Antoun PS, Maruyama M, Han S, Piccirillo G, Stucky M, Zipes DP, Chen PS, Das MK. Mechanisms of sinoatrial node dysfunction in a canine model of pacinginduced atrial fibrillation. Heart Rhythm ;7: Journal of Cardiac Arrhythmia