IDENTIFICATION OF CONCEALED POSTEROSEPTAL KENT PATHWAYS BY COMPARISONOF VENTRICULOATRIAL INTERVALS FROM APICAL AND POSTEROBASAL RIGHT-VENTRICULAR SITES

Background The differential diagnosis of supraventricular tachycardia with concentric atrial activation usually requires the inducibility of sustained tachycardia and needs a complex and time-consuming electrop hysiological evaluation. To develop a simple test to establish if vent riculoatrial conduction uses a posteroseptal accessory pathway or the normal conduction system, we compared the ventriculoatrial intervals d uring right ventricular pacing from apical and posterobasal sites. Met hods and Results Continuous pacing was performed from an apical and a posterobasal right ventricular site in 34 patients with retrograde con duction over the normal conduction system (group A) and in 22 patients with conduction over a posteroseptal accessory pathway (group B). Dur ing apical pacing, ventriculoatrial intervals in group A (176+/-40 mil liseconds) were not significantly different than those in group B (197 +/-47 milliseconds, P=NS). During posterobasal pacing, group B patient s had significantly shorter ventriculoatrial intervals than group A pa tients (158+/-46 versus 197+/-39 milliseconds, P<.01). The difference between the ventriculoatrial interval obtained during apical pacing an d that obtained during posterobasal pacing (ventriculoatrial index) di scriminated between the two groups without overlapping: It was positiv e in all group B patients (39+/-19; range, +10 to +70 milliseconds) an d negative in ail except two group A patients (-21+/-13; range, -50 to +5 milliseconds; P<.001). Conclusions This ventriculoatrial index can identify accurately and in the absence of tachycardia whether concent ric retrograde conduction is proceeding over a posteroseptal accessory pathway or over the normal conduction system.