The ventriculoatrial relationship after atrial overdrive pacing can help differentiate atrioventricular nodal reentrant tachycardia from junctional tachycardia.

PURPOSE: Differentiating between atrioventricular nodal reentrant tachycardia (AVNRT) and non-reentrant junctional tachycardia (JT) is difficult but highly necessary for catheter ablation. The purpose of this study was to investigate whether the ventriculoatrial (VA) relationship after atrial overdrive pacing (AOP) could help to distinguish AVNRT from JT.

METHODS: Thirty-eight AVNRT and 21 JT patients who were induced by infusion of isoproterenol after successful AVNRT ablation were paced through the high right atrium or coronary sinus until the ventricles were constantly captured. After the pacing was stopped, the intervals of postpacing VA (VAP) and tachycardia VA (VAT) were measured if the pacing did not terminate tachycardia.

RESULTS: Thirty-five (92.1 %) cases were captured by 119 AOPs (119/175) without terminating tachycardia in the 38 cases of AVNRT. Of the 35 cases, 34 (97.1 %) showed VAP-VAT < 22.55 ms in all successful AOPs (116 times). The remaining case showed VAP-VAT > 294.9 ms in one AOP and VAP-VAT < 22.55 ms in two AOPs. All 21 JT cases could be captured successfully by all (105/105) AOPs and showed VAP-VAT > 294.9 ms. VAP-VAT < 22.55 ms had 118/118 (100 %) specificity for AVNRT, and the VAP-VAT > 294.9 ms response was 105/105 (100 %) sensitive for JT.

CONCLUSIONS: The VA relationship after AOP could help distinguish AVNRT from JT. VAP-VAT < 22.55 ms was specific for AVNRT, and VAP-VAT > 294.9 ms for JT in the overwhelming majority, except for the rare instance of AVNRT with a double ventricular response.