Dual‐Loop Bi‐Atrial Macroreentrant Atrial Tachycardia in a Patient With Modified Cox Maze IV: Where Is the Initial Ablation Target?

Abstract

Case PresentationA 75-year-old man with atrial fibrillation, who underwent valve (mitral and tricuspid) plasty with a modified Cox-Maze IV, was referred for the ablation of atrial tachycardia (AT). At the beginning of the procedure, the baseline tachycardia cycle length (TCL) was 300 milliseconds. No pulmonary vein potentials were recorded, and a 3-dimensional (3D) activation map (CARTO, Biosense Webster Inc., Diamond Bar, CA, USA) showed a clockwise peri-mitral atrial tachycardia (PMAT) pattern (Fig. 1). With the entrainment pacing from the multiple sites at the left atrium (LA) in the 7-2 o'clock direction of the mitral annulus (MA), a postpacing interval (PPI)-TCL was ࣘ20 milliseconds (Fig. 1). The PPI-TCL at the multiple sites of the coronary sinus (CS) opposite of LA 3-6 o'clock direction of MA was ࣘ20 milliseconds, although the PPI-TCL at the LA 3-6 o'clock direction of MA was >20 milliseconds. Interestingly, the PPI-TCL at both the CS ostium and the right atrial septum was ࣘ20 milliseconds. Furthermore, the RA activation map showed that the counter-clockwise cavotricuspid isthmus (CTI) dependent AT although the PPI-TCL at the CTI was >20 milliseconds ( Fig. 1). Based upon these observations, where is the initial ablation target? CommentaryDual-loop AT was defined as the concomitance of 2 simultaneously reentrant circuits, a difference between the PPI and TCL from the dominant circuit of ࣘ20 milliseconds, and a sudden transformation to a new reentrant tachycardia maintained by the second circuit after ablation of the dominant tachycardia.1 Dual-loop AT is common in patients with postcardiac surgery, especially in correlation with congenital heart disease.2 Typically, the CTI dependent AT and the RA atriotomy-dependent AT present simultaneously. In this case, the 3D activation map of the initial AT demonstrated the concomitance of clockwise PMAT and counter-clockwise CTI dependent AT (Fig. 1). The initial PPI mapping revealed that the dominant tachycardia was the PMAT. The PPI mapping showed that the endocardial LA 3-6 o'clock direction of the MA opposite the CS was out of the reentrant circuit. Interestingly, both the CS and right atrium septum were part of the reentrant circuit. The reason for the reentrant circuit of PMAT including the bi-atrium and epicardium was that the modified Cox-Maze IV procedure, especially the radiofrequency line from the incisional line of the LA to the posterior MA, has been led to exclude the endocardial LA 3-6 o'clock direction of the MA from the reentrant circuit. Thereby, the tachycardia developed as bi-atrial AT utilizing the CS.Bi-atrial AT has been reported in patients after mitral valve plasty or ablation of the anterior LA line for PMAT.3,4 Interatrial conduction normally occurs via anatomically distinct connections such as the Bachmann bundle, around the fossa ovalis, and rarely in the CS.5 Anterior LA line ablation has been led to exclude the LA septal wall from the reentrant circuits of PMAT, and thereby AT has developed to bi-atrial AT via interatrial connections. ...

Dual-loop biatrial concomitant macroreentrant tachycardia in a patient without previous history of surgery or ablation

“…Complex macroreentrant atrial tachycardia is frequently related to structural heart disease, surgery, or ablation lesions. Dual-loop biatrial macroreentrant tachycardia has scarcely been reported3, 4 and also is related to postsurgery state. In this patient with no previous cardiac interventions, the counterclockwise atrial activation surrounding the tricuspid annulus might simply have given an initial impression of typical AFL.…”

“…Dual-loop atrial reentry was first described in patients who had previously undergone closure of atrial septal defects and the tachycardias were intra-atrial reentries 1, 2. There are only sporadic reports of biatrial tachycardias postsurgery or postablation 3, 4. We present a unique case of a dual-loop biatrial macroreentrant tachycardia, which developed in a patient without structural abnormality or previous cardiac interventions.…”