IMAGE Atrial flutter: Right, left, or both? Nicolas Clementy, MD, Bertrand Pierre, MD, Laurent Fauchier, MD, Dominique Babuty, MD From Cardiologie B Department, University François Rabelais, Tours, France. A 66-year-old man with a history of surgical removal of a left atrial myxoma was admitted to our department for radiofrequency ablation of a symptomatic atrial flut- ter. Baseline ECG showed atrial flutter with variable atrioventricular conduction and narrow QRS complexes (Figure 1). Atrial activity showed an aspect of intraatrial conduction delay. Echocardiography showed normal left ventricular function and no atrial dilation. Electrophysiologic study demonstrated a constant atrial cycle length of 420 ms, with clockwise activation within the right atrium. Entrainment maneuvers con- firmed a macroreentrant mechanism involving the right atrium. However, right atrial activation time covered only 70% of the total cycle length, and, surprisingly, coronary sinus activation was distal to proximal. An electroanatomic map of both the right and left atria through a transseptal approach was performed using the EnSite Velocity Cardiac Mapping System (St. Jude Med- ical, St. Paul, MN, USA). The three-dimensional color- coded time activation map showed a macroreentrant cir- cuit involving both atria (Figure 2, white arrows). The circuit, starting around the superior vena cava, reached the left atrium through the Bachmann bundle, descended around the right pulmonary veins down to the coronary sinus, and ended with clockwise activation of the right atrium with a slow conduction isthmus in the mid part of the right lateral wall. A radiofrequency ablation line applied to the high anteroseptal area of the right atrium terminated the flutter, and the arrhythmia was not rein- ducible. Postoperative atrial flutters are frequent after cardiac surgery and often are isthmus dependent. 1 Incisional atrial flutters following surgery for left atrial myxoma have been described, even with distal-to-proximal acti- vation of the coronary sinus. 2 We describe here the first documented case of a mac- roreentrant circuit requiring both atria. This mechanism has been suggested previously. 3 Three sites of transseptal breakthrough have been clearly discerned: high antero- septal right atrium at the putative insertion of the Bach- mann bundle, fossa ovalis, and region of the coronary sinus ostium. 4,5 In our case, the highly unusual reentrant circuit can be explained by the previous cardiac surgery. Removal of the left atrial myxoma performed first through a right atriotomy in the lateral wall was respon- sible for a slow conduction isthmus (Figure 2, area 1) and second through an interatrial septotomy was responsible for a scar that prevented descending activation of the interatrial septum (Figure 2, area 2). Activation then followed preferential conduction pathways to the left through the Bachmann bundle and back to the right through the coronary sinus, leading to biatrial macroreen- try. The aspect of bifid P waves in the inferior leads on ECG corresponded to superior-to-inferior activation of the superior part of the right atrium and then the left atrium through the Bachmann bundle. The near isoelec- tric part of the ECG pattern corresponded mostly to slow conduction within the right atrium. Successful ablation at the right insertion of the Bachmann bundle confirmed that the circuit was dependent on this structure. Address reprint requests and correspondence: Dr. Nicolas Clementy, Cardiologie B Department, Hospital Trousseau, 37044 Tours, France. E-mail address: nclementy@yahoo.fr. 1547-5271/$ -see front matter © 2012 Heart Rhythm Society. All rights reserved. 10.1016/j.hrthm.2010.12.029