Intermittent bundle branch blocks in a patient with uncommon-type atrioventricular nodal reentrant tachycardia and enhanced atrioventricular nodal conduction.

Abstract We report on a patient with uncommon-type atrioventricular (AV) nodal reentrant tachycardia with a short tachycardia cycle length (235–270 ms), in whom transient wide QRS tachycardia with both left bundle branch block and right bundle branch block aberrancy were followed by narrow QRS complexes. In addition, His-ventricular (H-V) block and a sudden prolongation of the H-V interval occurred during the tachycardia. As the determinant of these unusual findings, the possibility that the anterograde limb of the reentry circuit has an enhanced AV nodal conduction property is discussed, as is the clinical significance of this type of tachycardia.