Electrophysiological features differentiating the atypical atrioventricular node-dependent long RP supraventricular tachycardias.

BACKGROUND: Diagnosing atypical atrioventricular node-dependent long RP supraventricular tachycardias (SVTs) can be challenging.

METHODS AND RESULTS: Nineteen patients with 20 SVTs (atypical atrioventricular nodal reentrant tachycardia without [n=11]/with [n=3] a bystander nodofascicular [NF] accessory pathway, orthodromic reciprocating tachycardia [ORT] using a decremental atrioventricular [permanent form of junctional reciprocating tachycardia; n=4] or NF [NF reentrant tachycardia; n=2]) accessory pathway underwent electrophysiological study. Postpacing interval (PPI)-tachycardia cycle length (TCL), corrected PPI, VA (ventriculoatrial), HA (His-atrial), AH (atrio-His) values, and responses to His-refractory ventricular premature depolarizations were studied. Compared with atrioventricular nodal reentrant tachycardia, ORT patients were younger (42±13 years versus 54±19 years; P=0.036) and were women (5/6 [83%] versus 3/14 [21%]; P=0.036); TCLs were similar (435 ms versus 429 ms; 95% confidence interval, -47.5 to 35.5). PPI-TCL was shorter for ORT (118 ms versus 176 ms; 95% confidence interval, 26.3-89.7) but only 50% had PPI-TCL <115 ms, whereas 5 of 6 (83%) had PPI-TCL <125 ms (sensitivity, 83%; specificity, 100%). Corrected PPI <110 ms, VA <85 ms, and HA <0 ms had equivalent sensitivity (67%) and 100% specificity for ORT. Compared with permanent form of junctional reciprocating tachycardia, NF reentrant tachycardia/atrioventricular nodal reentrant tachycardia had longer AH (29 ms versus 10 ms; 95% confidence interval, 3.03-35.0) or AH(SVT)<AH(NSR) (normal sinus rhythm) His-refractory ventricular premature depolarizations advanced (4/8 [50%]), delayed (4/8 [50%]), or terminated (5/8 [63%]) SVT in all accessory pathway patients.

CONCLUSIONS: This unusual SVT requires separate maneuvers to delineate its upper and lower circuit. Standard entrainment criteria are modestly sensitive but highly specific for ORT; and PPI-TCL of 125 ms seems better than 115 ms. The AH criteria, or paradoxically AH(SVT)<AH(NSR), differentiates NF reentrant tachycardia/atrioventricular nodal reentrant tachycardia from permanent form of junctional reciprocating tachycardia. Bystander accessory pathways were only identified by His-refractory ventricular premature depolarizations.