Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Incorporating a “Superior” Slow Pathway

Abstract

Background— The existence of an atypical fast-slow (F/S) atrioventricular nodal reentrant tachycardia (AVNRT) including a superior (sup) pathway with slow conductive properties and an atrial exit near the His bundle has not been confirmed. Methods and Results— We studied 6 women and 2 men (age, 74±7 years) with sup-F/S-AVNRT who underwent successful radiofrequency ablation near the His bundle. Programmed ventricular stimulation induced retrograde conduction over a superior SP with an earliest atrial activation near the His bundle, a mean shortest spike-atrial interval of 378±119 milliseconds, and decremental properties in all patients. sup-F/S-AVNRT was characterized by a long-RP interval; a retrograde atrial activation sequence during tachycardia identical to that over a sup-SP during ventricular pacing; ventriculoatrial dissociation during ventricular overdrive pacing of the tachycardia in 5 patients or atrioventricular block occurring during tachycardia in 3 patients, excluding atrioventricular reentrant tachycardia; termination of the tachycardia by ATP; and a V-A-V activation sequence immediately after ventricular induction or entrainment of the tachycardia, including dual atrial responses in 2 patients. Elimination or modification of retrograde conduction over the sup-SP by ablation near the right perinodal region or from the noncoronary cusp of Valsalva eliminated and confirmed the diagnosis of AVNRT in 4 patients each. Conclusions— sup-F/S-AVNRT is a distinct supraventricular tachycardia, incorporating an SP located above the Koch triangle as the retrograde limb, that can be eliminated by radiofrequency ablation.

Unusual atrial activation recorded near the His bundle during supraventricular tachycardia: What is the mechanism?

“…A sup‐F/S‐AVNRT is a rare subtype of F/S AVNRT, with a site of earliest atrial activation located in the anteroseptal region near the HBE, and the superior SP is used as the retrograde limb on the reentrant circuit. Ablation could be successfully performed for tachycardia from the right atrial anteroseptal region, posterior to the HBE recording site, or from the noncoronary sinus of Valsalva without atrioventricular block . In the present case, retrograde superior SP was not observed during RV programmed stimulation at baseline.…”

“…However, the orthodromic AVRT was unlikely because RV overdrive pacing did not entrain the tachycardia other than the last RV pacing (Figure A). Furthermore, previous studies reported that the ventriculoatrial dissociation was characteristic of the sup‐F/S‐AVNRT and may be attributed to the lower common pathway …”

“…RV entrainment pacing was performed during the tachycardia, and ventriculoatrial dissociation was observed, followed by the termination without atrial capture, and retrograde conduction via FP was observed (Figure A). Therefore, the diagnosis of an atrial tachycardia was excluded and we considered the tachycardia as the atypical F/S AVNRT incorporating a superior SP, which was previously reported as sup‐F/S‐AVNRT . A diagnosis of orthodromic atrioventricular reentrant tachycardia (AVRT) using a slowly conducting accessory pathway as the retrograde limb was not completely excluded.…”

“…Therefore, the diagnosis of an atrial tachycardia was excluded and we considered the tachycardia as the atypical F/S AVNRT incorporating a superior SP, which was previously reported as sup-F/S-AVNRT. 1 A diagnosis of orthodromic atrioventricular reentrant tachycardia (AVRT) using a slowly conducting accessory pathway as the retrograde limb was not completely excluded. However, the orthodromic AVRT was unlikely because RV overdrive pacing did not entrain the tachycardia other than the last RV pacing (Figure 2A).…”

“…Furthermore, previous studies reported that the ventriculoatrial dissociation was characteristic of the sup-F/S-AVNRT and may be attributed to the lower common pathway. 1,2 The earliest atrial activation was recorded by the ablation catheter positioned in the anteroseptal region posterior to the HBE recording site during the sup-F/S-AVNRT, and RFA was applied, followed by the tachycardia termination ( Figures 2B and 3). This earliest atrial activation site was close to the unusual atrial activation site during the S/S AVNRT ( Figure 3B).…”