Ablation of atrial tachycardia originating from the vicinity of the atrioventricular node: significance of mapping both sides of the interatrial septum

OBJECTIVES The purpose of the study was to examine the value of right- and left-sided mapping to identify the site of tachycardia origin. BACKGROUND Focal atrial tachycardia may originate from the vicinity of the atrioventricular node from either side of the interatrial septum. METHODS In 16 patients undergoing radiofrequency catheter ablation of perinodal atrial tachycardia, activation mapping of the right and left side of the interatrial septum was performed. RESULTS Atrial tachycardia originated from the right side of the interatrial septum in 10 patients (group A) and from the left side in 6 patients (group B). On the right side, earliest atrial activity preceded the onset of the P-wave by 49 ± 15 ms in group A and by 38 ± 8 ms in group B (NS), and it preceded the signal recorded from the right atrial appendage by 59 ± 19 ms in group A and by 60 ± 13 ms in group B (NS). On the left side, earliest activity preceded the onset of the P-wave by 27 ± 16 ms in group A and by 51 ± 6 ms in group B (<0.01), and it preceded the signal obtained from the right atrial appendage by 38 ± 19 ms in group A and by 73 ± 9 ms in group B (<0.01). Atrial tachycardias were successfully eliminated in all patients without impairment of atrioventricular conduction. During follow-up, two patients had a recurrence of tachycardia. CONCLUSIONS Mapping of only the right side cannot exclude a left-sided origin. Therefore, mapping of both sides of the interatrial septum is required prior to ablation of focal atrial tachycardia originating from the vicinity of the atrioventricular node.