Unusual response to ventricular pacing maneuvers in narrow complex tachycardia—What is the mechanism?

two ventricular pacing maneuvers confirm the presence of a concealed NV/NF AP, however, whether it is a bystander during AVNRT or actively participating in the tachycardia mechanism remains unclear. The response of VOP entraining the tachycardia could not be obtained due to repeated termination of the tachycardia. Although, the presence of dual-AV nodal pathways and consistent VA relation during the tachycardia favor AVNRT as most likely etiology, orthodromic reciprocating tachycardia (ORT) using concealed NV/NF AP cannot be excluded This article is protected by copyright. All rights reserved.