Antidromic reciprocating tachycardia: What is the mechanism of termination?

Abstract

Q c n A t m t i p t i ase presentation lectrophysiologic study was performed in a 24-year-old oman with Wolff-Parkinson-White syndrome who preented with a preexcited, regular tachycardia that terminated ith adenosine. The polarity of the delta wave was positive waves in eads I and aVL, negative in III and aVF, and isoelectric in I. The precordial transition occurred in V3. In the baseline tate, there was no ventriculoatrial conduction. Anterograde ccessory pathway (AP) conduction was decremental, with block cycle length of 370 ms. On isoproterenol, ventriculoatrial conduction was midine and decremental, with the earliest atrial activation in he proximal coronary sinus, consistent with conduction hrough the AV node. The anterograde block cycle length of he AP was 310 ms. Antidromic reciprocating tachycardia ith a cycle length of 315 to 325 ms was induced by entricular extrastimulus testing. There was no evidence of second AP. The tachycardia terminated spontaneously on everal occasions in a reproducible fashion (Figure 1). What s the mechanism of termination?