Entrainment for Distinguishing Atypical Atrioventricular Node Reentrant Tachycardia From Atrioventricular Reentrant Tachycardia Over Septal Accessory Pathways With Long Right Ventricular Tachycardia

Background-The response to right ventricular (RV) entrainment is useful to distinguish atypical AV node reentrant tachycardia from AV reentrant tachycardia using a septal accessory pathway. Whether entrainment can differentiate between AV node reentrant tachycardia and AV reentrant tachycardia in patients with long-RP tachycardia has not been systematically validated. Methods and Results-Twenty-four patients with concealed septal accessory pathways who had an electrophysiology study between January 1, 2000, and January 1, 2010, were included (age, 38 +/- 17 years; men, 17). Entrainment was performed from the RV apex pacing at cycle length 20 to 40 ms shorter than tachycardia cycle length (TCL). The mean TCL was 390 +/- 80 ms, the mean AH interval during tachycardia was 151 +/- 57 ms, and the mean ventriculoatrial (VA) time was 182 +/- 103 ms. Twelve patients had typical accessory pathways (VA/TCL <40%), and 12 had slowly conducting accessory pathways (VA/TCL >= 40%). In all patients with typical accessory pathways, the postpacing interval minus the TCL (PPI-TCL) was <115 ms and the difference in the VA interval during pacing and tachycardia (StimA-VA) was <85 ms. On the other hand, in 6 of the 12 patients in the slowly conducting group, the PPI-TCL was >115 ms, and the StimA-VA was >85 ms. Conclusions-Slowly conducting accessory pathways frequently yield RV entrainment criteria traditionally attributable to AV node reentry. Distinguishing AV node reentry from AV reentry in patients with long-RP tachycardia requires other criteria. (Circ Arrhythm Electrophysiol. 2011; 4: 506-509.)