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

We report on a patient with uncommon-type atrioventricular (AV) nodal reent rant tachycardia with a short tachycardia cycle length (235-270 ms), in who m transient wide QRS tachycardia with both left bundle branch block and rig ht 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 unusu al Endings, the possibility that the anterograde limb of the reentry circui t has an enhanced AV nodal conduction property is discussed, as is the clin ical significance of this type of tachycardia.