Key result
Sub-threshold stimulation safely interrupts uncommon AVNRT without capture in ~82% of successful ablation sites.
Why the study?
Sub-threshold stimulation has been shown to characterize target sites for slow pathway ablation in common AVNRT but has not been investigated in fast-slow and slow-slow AVNRT variants.
Does sub-threshold stimulation mapping effectively identify target sites for slow pathway ablation in patients with uncommon variants of AVNRT?
Observational (n=17)
Does sub-threshold stimulation mapping effectively identify target sites for slow pathway ablation in patients with uncommon variants of AVNRT?
Sub-threshold stimulation mapping is highly effective for identifying successful slow pathway ablation sites in uncommon variants of AVNRT, demonstrating high positive and negative concordance with ablation outcomes.
Sub-threshold stimulation may identify ablation targets in uncommon AVNRT; leaves open need for randomized validation before practice change.
AIM: Sub-threshold stimulation (STS) applied during atrioventricular nodal re-entrant tachycardia (AVNRT) of the common (slow-fast) type has been shown to effectively characterise target sites suitable for slow pathway (SP) ablation but has not been investigated in the setting of fast-slow and slow-slow variants. METHODS AND RESULTS: Seventeen consecutive patients (52+/-16 years, 12 female) with sustained uncommon type AVNRT (fast-slow: n = 13, slow-slow: n = 4) were investigated. Mapping of the SP was started postero-septally close to the coronary sinus ostium and continued toward mid-septal sites, if required. Target sites for STS were selected according to established criteria including the recording of the earliest retrograde atrial activation during AVNRT. Long duration (5 s) constant current STS during AVNRT variants was performed in a stepwise manner (max 5 mA) at each site eligible for SP ablation until termination or capture occurred. Radiofrequency current (RFC) was delivered following successful STS termination of tachycardia (65 degrees C, 60 s) and exclusion of catheter dislodgement. Uncommon AVNRT with a mean cycle length of 405+/-70 ms was induced without spontaneous termination in all patients. Interruption of AVNRT variants due to selective STS-induced block of the retrograde (n = 12) or anterograde (n =2) SP occurred without capture in 14/17 (82%) patients. This was exclusively observed at sites with successful subsequent RFC application. AVNRT was rendered non-inducible in all patients after a median of 1 (1-11) RFC pulses without complications. CONCLUSIONS: Uncommon AVNRT can be interrupted by STS delivered at subsequently successful target sites for SP ablation in most patients (82%). The high positive and negative concordance between the effects of STS and following RFC application indicates that STS-mapping is also useful in the setting of AVNRT variants.
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Stephan Willems (2004) conducted an observational in Sustained uncommon type atrioventricular nodal re-entrant tachycardia (AVNRT) (n=17). Sub-threshold stimulation (STS) was evaluated on Interruption of AVNRT variants due to selective STS-induced block without capture. Sub-threshold stimulation successfully interrupted uncommon AVNRT variants without capture in 82% of patients at sites with successful subsequent radiofrequency ablation.
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