Atrioventricular Nodal Reentrant Tachycardia with 2:1 Atrioventricular Block

This report illustrates an interesting case of atrioventricular nodal reentrant tachycardia that presented with 2 different ventricular cycle lengths due to a 2:1 block in the lower common pathway. At the induction of the tachycardia, a long-short sequence above the His creates a phase 3 block resulting in a 2:1 conduction in the lower common pathway. A premature ventricular contraction, by retrograde penetration of the His, eliminates the long-short sequence and brings the conduction back to 1:1.