Key result
The number of beats in the transition zone with fixed SA interval during ventricular overdrive pacing distinguished right- versus left-sided accessory pathways using a cutoff >2 beats (P<0.001).
Why the study?
Does the number of beats in the transition zone with fixed SA interval during right ventricular overdrive pacing predict accessory pathway location in orthodromic reentrant tachycardia?
Observational (n=77)
Does the number of beats in the transition zone with fixed SA interval during right ventricular overdrive pacing predict accessory pathway location in orthodromic reentrant tachycardia?
Assessing the number of beats in the transition zone with fixed SA interval during right ventricular overdrive pacing is a simple and effective maneuver to determine accessory pathway location in orthodromic reentrant tachycardia.
May aid accessory pathway lateralization during ventricular pacing in ORT; leaves open prospective validation before routine use.
BACKGROUND: Ventricular overdrive pacing (VOP) produces reset during the transition zone (TZ) of QRS fusion in orthodromic reentrant tachycardia (ORT) and after the TZ in atrioventricular nodal reentrant tachycardia (AVNRT), and this represents a simple diagnostic maneuver to differentiate the two tachycardia mechanisms. OBJECTIVE: The purpose of this study was to determine whether the number of beats with reset in the TZ predicts accessory pathway (AP) location in ORT. METHODS: We retrospectively reviewed 57 patients with ORT (21 left-sided AP, 20 septal AP, and 16 right-sided AP) and 20 patients with AVNRT (19 typical AVNRT and one atypical AVNRT) who underwent VOP from the right ventricular apex. We analyzed the number of beats with reset during or after the TZ, demonstrated by fixed ventricular stimulus-atrial (SA) interval during VOP. RESULTS: The overall mean tachycardia cycle length [CL] minus VOP CL was 22.6 ± 7.5 ms with no statistical difference between the groups (P = 0.480). The mean number of beats in the TZ with fixed SA interval was 2.5 ± 1.4 for the whole ORT group, 1.1 ± 0.4 for left-sided AP (range 1-2), 2.8 ± 0.9 for septal AP (range 1-5), and 4.0 ± 0.9 for right-sided AP (range 3-6) (P < 0.001). Using a cutoff >2 beats distinguished right- versus left-sided AP in all cases. CONCLUSION: Assessing the number of beats in the TZ with fixed SA interval during VOP helps to determine AP location in ORT and adds valuable information to an established simple diagnostic pacing maneuver, especially when a two-catheter simplified approach is employed.
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Åkerström et al. (2015) conducted an observational in Orthodromic reentrant tachycardia and atrioventricular nodal reentrant tachycardia (n=77). Ventricular overdrive pacing was evaluated on Number of beats in the transition zone with fixed SA interval (p=<0.001). The number of beats in the transition zone with fixed SA interval during ventricular overdrive pacing distinguished right- versus left-sided accessory pathways using a cutoff >2 beats (P<0.001).
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