Analyses of the Mode of Termination During Diagnostic Ventricular Pacing to Differentiate the Mechanisms of Supraventricular Tachycardias.

OBJECTIVES: The goal of this study was to determine the diagnostic yield of analyzing the mode of termination during ventricular overdrive pacing (VOP) to differentiate the mechanisms of supraventricular tachycardias (SVTs).

BACKGROUND: The majority of the diagnostic criteria for VOP rely on successful entrainment, but termination of SVTs is common during VOP.

METHODS: We studied 225 SVTs with a 1:1 atrioventricular relationship, including 34 atrial tachycardias, 67 orthodromic reciprocating tachycardias (ORTs) (including 4 ORTs using accessory pathways [APs] with decremental properties), and 124 atrioventricular nodal re-entrant tachycardias. The total pacing prematurity (TPP) needed to reset or terminate the SVT was calculated by using a simplified method, and the post-pacing interval minus the tachycardia cycle length (PPI - TCL) was predicted from the TPP.

RESULTS: VOP terminated 87 SVTs (39%). No atrial tachycardias were terminated by VOP in this study. SVT termination occurred after (n = 71) or before (n = 16) atrial resetting. The predicted PPI - TCL was highly correlated with the measured PPI - TCL (r = 0.96; p < 0.001). The TPP had diagnostic accuracy equivalent to the predicted PPI - TCL. The TPP was measurable irrespective of the termination mode and correctly diagnosed ORTs with decremental APs. All ORTs using septal APs and no atrioventricular nodal re-entrant tachycardias had a TPP <125 ms. Considering other criteria evaluable in terminated SVTs, a combined criteria of a TPP <125 ms and atrial capture/termination within the fusion period were specific for ORTs using free-wall APs, except for left anterolateral/lateral sites.

CONCLUSIONS: The termination analyses were useful for differential diagnoses of SVTs terminated during VOP.