Tachycardia induction with ventricular extrastimuli differentiates atypical atrioventricular nodal reentrant tachycardia from orthodromic reciprocating tachycardia

BackgroundDifferentiating atypical atrioventricular nodal reentrant tachycardia (AVNRT) from septal orthodromic reentrant tachycardia (ORTSeptal) is challenging in nonsustained tachycardia. When sustained, the postpacing interval minus tachycardia cycle length following entrainment (PPIEntrainment − TCL) and stimulation to atrial interval minus ventriculoatrial interval (Stim-AEntrainment − VA) are utilized.ObjectiveWe hypothesized that the first tachycardia cycle after tachycardia induction with right ventricular apical extrastimulation would yield comparable information to entrainment, precluding the need for sustained tachycardia.MethodsTwenty-four patients with AVNRT (age 47 ± 18 years), 19 with ORTSeptal (age 42 ± 17 years), and 15 with ORT over a left lateral accessory pathway (ORTLeft) (age 41 ± 16 years) were included. The ventricular extrastimulus to atrial depolarization at tachycardia initiation (Stim-AInitiation) and tachycardia VA interval were measured to establish the Stim-AInitiation minus VA interval (Stim-AInitiation − VA). The ventricular extrastimulus to the subsequent right ventricular apical depolarization (postpacing interval at initiation, PPIInitiation) was utilized to obtain the PPIInitiation minus TCL (PPIInitiation − TCL). The AH interval associated with the PPIInitiation minus the AH in tachycardia was utilized to establish a corrected PPIInitiation minus TCL (cPPIInitiation − TCL).ResultsThe intervals after tachycardia initiation were longer for AVNRT than for ORT: mean PPIInitiation − TCL (193 ± 44 vs 91 ± 73; P <.001), cPPIInitiation − TCL (174 ± 44 ms vs 88 ± 50 ms; P <.001), and Stim-AInitiation − VA (161 ± 45 ms vs 69 ± 53 ms; P <.001). The correlation coefficient for Stim-AInitiation minus VA against Stim-AEntrainment minus VA was 0.79 and for cPPIInitiation minus TCL against PPIEntrainment minus TCL was 0.71. cPPIInitiation minus TCL <115 ms or Stim-AInitiation − VA <85 ms was observed only in ORT. The converse was observed in AVNRT but also in ORTSeptal over decremental accessory pathways and ORTLeft.ConclusionStim-AInitiation − VA < 85 ms or cPPIInitiation − TCL < 115 ms excludes AVNRT.