A novel approach to differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia

BACKGROUND Various diagnostic maneuvers have been proposed to help differentiate orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal reentrant tachycardia (AVNRT) prior to ablation. However, not all criteria are applicable in every situation as each has limitations. OBJECTIVE The purpose of this study was to determine whether the behavior of tachycardia during onset of right ventricular (RV) pacing would help differentiate ORT from AVNRT. METHODS We retrospectively reviewed 72 cases (42 typical AVNRT, 7 atypical AVNRT, 15 left free-wall pathways, 6 septal pathways, 2 right free-wall pathways). We assessed the number of beats required to accelerate the tachycardia cycle length (TCL) to the paced cycle length (PCL) once a fully RV paced complex was achieved during supraventricular tachycardia. RESULTS In the AVNRT group, delta cycle length (DCL = PCL-TCL) was 29 +/- 16 ms compared to 29 +/- 10 ms in ORT group (P = NS). In the AVNRT group, the average number of fully RV paced beats required to reset the tachycardia was 3.7 +/- 1.1 compared to 1 +/- 0 in the ORT group (P <.0001). Using a cutoff >1 beat yielded both positive and negative predictive values of 100% for diagnosing AVNRT versus ORT. During entrainment attempts, AVNRT terminated 51% of the time and ORT terminated 65% of the time but still allowed application of the new criterion. CONCLUSION Assessing timing and type of response of supraventricular tachycardia to RV pacing can help differentiate ORT from AVNRT with high certainty and prevent the need for other pacing maneuvers and measurements.