Negative SA-VA interval during overdrive ventricular pacing terminating long RP supraventricular tachycardias: a new diagnostic criterion for atrial tachycardia

Introduction and objective We have recently reported that the stimulus–atrial interval during ventricular entrainment (SA) minus the ventriculo–atrial (VA) interval during supraventricular tachycardia (SVT) is negative in 100% of atrial tachycardias (AT) with ventriculoatrial conduction and positive in 100% of the remaining SVTs. This finding could be of particular practical interest in "non-entrainable" SVTs with a long VA interval, where overdrive pacing consistently terminates the tachycardia, making post-entrainment response impossible to assess. However, its usefulness in this setting has not yet been evaluated. Methods Long VA SVTs that terminated with right apical ventricular (RVA) overdrive pacing after modifying the AA interval were retrospectively and consecutively collected from two centers. Long VA SVT was defined by a VA interval ≥50% of the R–R or V-V Interval. Intervals were measured from the QRS onset to the earliest septal atrial electrogram. The SA interval was measured on the first beat of the pacing train that modified the timing of the atrial electrogram. The final diagnosis [AT, atrioventricular nodal reentry (AVNRT), AV reentry (AVRT)] was established using standard electrophysiological criteria. The optimal SA–VA cutoff value for the diagnosis of AT was determined by receiver operating characteristic (ROC) curve analysis. Results Among 172 long RP SVTs analyzed, RVA overdrive pacing successfully modified the AA interval and terminated the tachycardia in 20 cases: 4 (20%) AVNRT, 4 (20%) AVRT, and 12 (60%) AT. As shown in Table 1, AT had longer cycle lengths (416 ± 67 ms vs. 343 ± 38 ms; p=0.009), longer VA intervals (286 ± 74 ms vs. 209 ± 49 ms : p=0.025), and shorter SA intervals (169 ± 43 vs. 270 ± 60; p =0.003] although with some overlap between groups. In contrast, all ATs exhibited a negative SA–VA interval (−117 ± 91 ms), whereas all the remaining SVTs had positive SA–VA values (61 ± 35 ms); p < 0.001. A cutoff value of SA–VA < 0 ms provided an area under the curve of 1.0 for the diagnosis of AT. Conclusion In long-RP SVTs where overdrive ventricular pacing modifies the AA interval and terminates the tachycardia, a negative SA–VA interval reliably differentiates AT from other forms of SVT. This criterion may therefore provide additional diagnostic value in this uncommon and challenging subgroup of SVTs, in which the post-entrainment response cannot be evaluated.