Atrial induction in patients with fast-slow AVNRT revealed an incremental response in 35% of cases, driven by excessive shortening of the retrograde conduction time over a slow pathway.
Observational (n=33)
In specific patients with F/S-AVNRT, a shortening of retrograde conduction time over a slow pathway is manifested during atrial induction, contributing to cyclic variability.
INTRODUCTION: Electrophysiological properties of reentry circuits of fast-slow atrioventricular nodal reentrant tachycardia (F/S-AVNRT) may contribute to cyclic variability after atrial induction. METHODS: In 156 atrial inductions of 33 patients with F/S-AVNRT, we measured the atrio-His (AH) and His-atrial (HA) intervals in the first cycle after the induction (AH1 and HA1, respectively), those in the second cycle (AH 2 and HA 2, respectively), and those during tachycardia that maintained a stable cycle length AHT and HAT, respectively), and calculated the value of AH(1) minus AH(T) ΔAH and the value of HA(1) minus HA(T) ΔHA in each induction. According to the sum of ΔAH and ΔHA, tachycardia variability was classified as incremental (20). RESULTS: ΔAH and ΔHA were significantly different between the three responses: 6 ± 28 and -67 ± 39 in 55 inductions (35%) with an incremental response, 20 ± 10 and -23 ± 28 in 59 (38%) with a balanced response, and 54 ± 44 and 4 ± 50 in 42 (27%) with a decremental response, respectively. Incremental response was reproducibly and consistently observed in 33% of patients. HA(2) was similar to HA(T) in inductions with an incremental response. These results suggest that incremental response can be manifested only in the first cycle when HA(1) is excessively shortened, approximating a retrograde conduction time over a slow pathway, in contrast, and far superior to a decremental delay of AH(1). CONCLUSION: In specific patients with F/S-AVNRT, poorly recognized, electrophysiological properties of shortening a retrograde conduction time over a slow pathway was manifested during atrial induction.
Tamura et al. (Thu,) conducted a observational in fast-slow atrioventricular nodal reentrant tachycardia (F/S-AVNRT) (n=33). Atrial induction was evaluated on Tachycardia variability (incremental, balanced, or decremental response based on sum of ΔAH and ΔHA). Atrial induction in patients with fast-slow AVNRT revealed an incremental response in 35% of cases, driven by excessive shortening of the retrograde conduction time over a slow pathway.