Electrophysiological characteristics
At EPS, the average presenting sinus rhythm cycle length was 857 ± 207 milliseconds (ms) with a baseline A-H interval of 86.6 ± 20.4ms and a H-V interval of 42.7 ± 7.4ms. At baseline, retrograde VA conduction was present at a pacing cycle length of 600ms in 60 (89.6%) patients. The remaining 7 (10.4%) demonstrated VA conduction with use of isoproterenol. Overall, 10 (14.9%) patients required isoproterenol for AVNRT induction. Antegrade refractory period testing demonstrated an AH jump of >50ms in 42 (70.0%) patients with an average jump of 78.5 ± 43.1ms. The fast pathway effective refractory period (ERP) was 347 ± 64ms and slow pathway ERP was < 283 ± 46ms. AV nodal Wenckebach was at 373 ± 75ms. AVNRT was inducible in all patients with a combination of atrial pacing manoeuvres including single atrial extras, sensed atrial doubles and triple extra stimuli. The mean AVNRT cycle length was 370 ± 64ms with a septal VA timing of 25.7 ± 23.2ms.