A 65 year-old with history of prior ablations for regular narrow QRS
short- RP tachycardia presented with recurrence of palpitations. An
electrophysiological study showed long VA tachycardia with concentric
atrial activation with a left ventricular origin extrastimulus delivered
during His refractoriness, advancing the next ‘A’. A HRVPB can only
reset an ORT if it ‘pulls in’ the local V at the ventricular insertion
of an accessory pathway. As showcased in this case, erudite analysis of
the pattern of perturbation of local ventricular electrograms is of
paramount significance when interpreting responses to this maneuver.
This concept when fortified with a heightened index of clinical
suspicion for mitral annular block, anatomical knowledge of the pattern
of LA-CS muscular connections, and pathway orientation, led to accurate
electrophysiological diagnosis and management.