Spiral slow conduction associated with a box isolation in the posterior left atrium unmasking a pulmonary vein reconnection

Figure 1. A: An activation map during coronary sinus (CS) pacing before the box isolation (BOXI). B: A unidirectional reconnection from the left atrium (LA) to the right-sided pulmonary veins (RPVs; left panel) and exit block from the right inferior pulmonary vein (RIPV) to the posterior LA (right panel) during the BOXI. Activation maps during CS pacing after the BOXI demonstrated C: conduction from the inferior LA to the right side of the posterior LA through the conduction gap on the inferior BOXI line; D: inferior-to-superior conduction on the right side of the posterior LA; E, F: turning around from the right to left side of the posterior LA; G: superior-to-inferior slow conduction on the left side of the posterior LA; and H: suspected epicardial conduction from the left side of the posterior LA to the RIPV. The red tags and dark red on the maps represent the radiofrequency application sites and activation wavefront, respectively. The white solid and dotted arrows on the maps and black arrows on the electrocardiograms indicate the endocardial and epicardial activation propagation and P waves during sinus rhythm, respectively. All activation maps and the online video were created using…

Figure 2. A: Transient elimination of the connection between the left side of the posterior left atrium (LA) and right inferior pulmonary vein (RIPV) during ongoing ablation (∗). B: Completion of the box isolation (BOXI) with a radiofrequency (RF) application at the conduction gap on the inferior BOXI line (∗∗). Coronary sinus (left panel) and posterior LA (right panel) pacing demonstrated entrance and exit block of the BOXI, respectively, and the conduction from the posterior LA to the RIPV still persisted after completing the BOXI. C: Final RF ablation sites on the postablation voltage map. The yellow and white tags represent the RF ablation sites with completion of the BOXI and transient conduction block between the posterior LA and RIPV, respectively. ABL 1-2 and 3-4 = distal and proximal ablation catheter recordings. Abbreviations are as in Figure 1.