PO-05-146 AN UNUSUAL ATRIOVENTRICULAR REENTRY TACHYCARDIA: SUCCESSFUL ABLATION OF NOVEL SLOW PATHWAY AT SUPERIOR SEPTAL PERIMITRAL LEFT ATRIUM

Abstract

Atrioventricular nodal reentrant tachycardia (AVNRT) is a common supraventricular tachycardia (SVT), treated with catheter ablation of slow pathway. The right and left inferior slow pathway (SP) extensions of the AV node are widely recognized, but other SPs are very rare. We present a case of atypical AVNRT that was successfully ablated at the superior septal perimitral left atrium. N/A A 75-year-old man with history of coronary artery disease status post coronary artery bypass grafting and recurrent episodes of symptomatic SVT despite diltiazem and metoprolol presented for catheter ablation. Mid RP SVT (cycle length, CL 350 ms) with concentric atrial activation was inducible with atrial and ventricular extrastimulation. Synchronized premature ventricular complexes and ventricular entrainment excluded AV reentry. Very late coupled premature atrial complex from coronary sinus (CS) delivered synchronous to septal A activation delayed next A and reset SVT indicating AVNRT and excluding ectopic junctional (JT) or atrial tachycardia (AT). Further, AH interval during SVT was much longer than AH with atrial pacing at same CL excluding AT. We concluded mechanism to be atypical AVNRT. On activation mapping of right atrium, earliest A was recorded in the fast pathway region, earlier than locations of right and left slow pathways in the triangle of Koch and CS respectively. Radiofrequency ablation lesions anatomically targeting both slow pathways were delivered at base of triangle of Koch and inside CS without affecting SVT. High density activation maps of both right and left atria were created during SVT using Orion basket catheter and Rhythmia (Boston Scientific) mapping system. Earliest A was recorded in the superior septal perimitral left atrium, superior to the location of His bundle electrogram, and anatomically adjacent to aortic sinuses of Valsalva (not mapped). We concluded this to be an unusual left superior extension of the AV node. Radiofrequency ablation lesion using IntellaNav MiFi catheter at this site promptly terminated SVT. Consolidation lesions were delivered and anchored to the mitral annulus. The tachycardia was no longer inducible on programmed electrical stimulation despite isoproterenol. The patient has remained symptom free for 6 months since ablation. With activation mapping we identified the retrograde slow pathway participating in an unusual atypical AVNRT at superior septal perimitral left atrium.