Abstract 2520: A New Criterion for Diagnosis of Accessory Pathway Using the H-H and A-A Intervals of the First Entrained Cycle During Ventricular Overdrive Pacing
Background: Advancement of succeeding atrial activation by a ventricular extrastimulus (VES) applied at the time of His refractoriness during supraventricular tachycardia (SVT) has been used as a proof of existence of an accessory pathway (AP). This study tested usefulness of a new criterion for diagnosis of AP using the H-H and A-A intervals of the first entrained cycle during ventricular overdrive pacing (VOD), in comparison with the conventional VES method.
Methods: In 48 pts with SVT (19 men, mean age 44 ± 18 yrs, 26 pts with AP and 22 pts without AP), a VES was elicited at the time of His deflection during SVT. VOD was subsequently performed from the right ventricular apex during SVT at cycle lengths (CLs) 30–40 ms shorter than the SVT CL. With the beginning of VOD, the A-A interval shortened from SVT CL to pacing CL in a few beats. When the A-A interval became equal to the pacing CL, the cycle was considered as the first entrained cycle, and the H-H interval preceding the A-A interval was measured.
Results: VES advanced the next atrial activation in 14 (54%) pts with AP and in no pts without AP. The H-H interval during VOD could be measured in all pts with AP and in 16 (73%) pts without AP. The H-H interval of the first entrained cycle was longer than the pacing CL by 15 ms or more (Figure A⇓) in all pts with AP but was equal to the pacing CL (Figure B⇓) in all pts without AP in whom the H-H interval could be measured. The criterion, H-H > A-A by 15 ms or more for the first entrained cycle, provided a higher diagnostic yield for presence of an AP compared to the VES method (P <0.001).
Conclusion: Our new criterion reliably diagnoses presence of an AP in pts with SVT, with higher sensitivity compared to the conventional VES method.