ECG & EP CASES Young-Keun On, MD, PhD Division of Cardiology, Department of Medicine Cardiac & Vascular Center, Samsung Medical Center Sungkyunkwan University School of Medicine, Seoul, Korea A case of paroxysmal antidromic atrioventricular reentrant tachycardia with AF ABSTRACT n the Wolff-Parkinson-White (WPW) syndrome, atrioventricular (AV) conduction occurs through an AV bypass tract, which results in earlier activation (preexcitation) of the ventricles. Antidromic atrioventricular reentrant tachycardia (AVRT) is characterized by a wide QRS complex and ventricular rates of up to 250 beats/min. The width of the preexcited QRS complex and the amplitude of the ST-T wave segment usually obscure the retrograde P wave on the surface ECG. The rhythm of preexcited atrial fibrillation (AF) is exceptionally irregular, and can be associated with very rapid ventricular responses caused by the nondecremental anterograde AV conduction over the bypass tract. A shortest preexcited RR interval of less than 250 milliseconds during sustained AF is a very sensitive marker of the risk of VF in WPW syndrome. Catheter ablation is considered first-line therapy for patients with WPW syndrome. Key words: Wolff-Parkinson-White (WPW) syndrome antidromic atrioventricular reentrant tachycardia (AVRT) catheter ablation Received: April 1, 2011 Accepted: June 29, 2011 Correspondence: Young-Keun On, MD, PhD, Division of Cardiology, Department of Medicine Cardiac & Vascular Center, Samsung Medical Center Sungkyunkwan University School of Medicine, 50 rwon-dong Gangnam-gu, Seoul, Korea, 135-710 Tel: 82-2-3410-3420, Fax: 82-2-3410-3849 E-mail: yk.on@samsung.com 45

avr V4 avl V2 V5 V3 V6 Figure 1. Surface electrocardiogram showed the wide QRS tachycardia with irregular heart rhythm, which revealed positive QRS in the precordial and inferior leads. 46 Journal of Cardiac Arrhythmia

avr V4 avl V2 V5 V3 V6 ECG & EP CASES Figure 2. Surface electrocardiogram showed the normal sinus rhythm with pre-excitation, which revealed positive QRS in the precordial and inferior leads. avr V4 avl V2 V5 V3 V6 Figure 3. Surface electrocardiogram during tachycardia showed the wide QRS tachycardia with positive QRS in the precordial and inferior leads. 47

200 ms V 6 HRA dist HRA prox HS dist HS prox CS 9,10 CS 7,8 CS 5,6 CS 3,4 CS 1,2 RVa dist RVa prox stm 2 4:04:52 PM 4:04:53 PM 4:04:54 PM Figure 4. ntracardial electrogram showed the atrial fibrillation. 200 ms V 6 HRA dist HRA prox HS dist HS prox CS 9,10 282 msec 212 BPM CS 7,8 CS 5,6 CS 3,4 CS 1,2 RVa dist RVa prox stm 2 4:11:44 PM 4:11:45 PM 4:11:46 PM Figure 5. ntracardial electrogram showed the atrioventricular reentrant tachycardia with antegrade conduction through the left anterolateral accessory pathway. 48 Journal of Cardiac Arrhythmia

RAO LAO Figure 6. Fluoroscopy showed that the radiofrequency catheter was located at the ateral site of the mitral annulus. References 1. Morady F. Catheter ablation of supraventricular arrhythmias: State of the Art. Pacing Clin Electrophysiol. 2004;27:125-142. 2. Scheinman M, Calkins H, Gillette P, et al: NASPE policy statement on catheter ablation: personnel, policy, procedures, and therapeutic recommendations. Pacing Clin Electrophysiol. 2003;26:789. 3. Zipes DP, Jalife J. Cardiac Electrophysiology, From cell to bedside, 5th ed, Saunders, 2009. 49