Multiple reentrant tachycardias due to retrograde conduction of dual atrioventricular bundles with atrioventricular nodal-like properties.

A patient is presented who had two paroxysmal supraventricular tachycardias, one slow and incessant and the other fast. Both paroxysmal tachycardias appeared to be atrioventricular (A-V) reentrant, with anterograde conduction by way of a normal A-V pathway. Two pathways conducting in retrograde manner were demonstrated, characterized by different conduction times (fast and slow), identical abnormal atrial activation sequence and A-V nodal-like properties (retrograde Wenckebach periodicity with rapid ventricular pacing, and depression with ouabain and propranolol). Thus, there appeared to be two anomalous A-V bundles with nodal-like properties conducting in retrograde fashion. Whether the paroxysmal tachycardia was fast or slow depended on which of these pathways was utilized. Spontaneous cure of incessant paroxysmal tachycardia was observed and coincided with unexplained total loss of ability for ventriculoatrial conduction.