The stimulus-atrial minus ventriculo-atrial interval (SA-VA difference) during ventricular overdrive pacing of a supraventricular tachycardia is used to differentiate atrioventricular reciprocating tachycardia (AVRT) from atrioventricular nodal re-entrant tachycardia (AVNRT), but positive values have always been reported. In atrial tachycardia, the SA conduction is unrelated to the tachycardia mechanism, allowing for negative SA-VA values. We postulated that a negative SA-VA may serve as a criterion for atrial tachycardia in patients with supraventricular tachycardia and ventricular overdrive pacing from the right ventricular apex.

Multicenter data from ventricular overdrive pacing during atrial tachycardia (from 6 centers) and during AVRT and AVNRT (from 2 centers) were retrospectively and consecutively collected. The correct diagnosis was established using conventional criteria. The SA-VA difference was calculated for each case. The optimal SA-VA cut-off point for the diagnosis of atrial tachycardia was determined.

Out of 240 tachycardias analyzed, ventricular overdrive pacing succeeded in accelerating the atria to the pacing rate without tachycardia termination in 106 cases: 38 (36%) AVNRT, 33 (31%) AVRT, and 35 (33%) atrial tachycardias (all exhibiting long VA intervals). All atrial tachycardias had a negative SA-VA value, while all AVNRT and AVRT cases had positive SA-VA values. A SA-VA value lower than 0ms was the best cutoff, with an area under the curve of 1 and 100% sensitivity and specificity for the diagnosis of atrial tachycardia.

A negative SA-VA difference is a novel and accurate criterion for the diagnosis of atrial tachycardia with long VA intervals.

.