Intercaval bundle connecting posterosuperior right atrium to right superior pulmonary vein detected during catheter ablation for atrial fibrillation

Catheter ablation of atrial fibrillation (AF) is one of the most complex interventional electrophysiologic procedures. Since the ectopic supraventricular beats and paroxysms of AF originating from pulmonary veins (PV) was first observed (1), pulmonary vein isolation (PVI) became the primary treatment target of AF catheter ablation. The entrance and exit blocks in the PVs confirm successful PVI. Inability to achieve PVI and PV reconnection, which can be observed very early after procedure (2), are frequent causes of AF recurrence and necessitate a repeat procedure (3). When circumferential PV antral ablation fails to achieve PVI, it is usually due to a gap in the ablation line. When the gap is mapped and successfully ablated, durable PVI is usually achieved. Another possible cause of persistent PV conduction is an interesting and probably rare phenomenon, in which the designated exit and entrance site for conduction is an intercaval bundle (IB), an anatomical structure that connects one of the PVs to the right atrium (4). IC has been previously defined in anatomical studies of the heart (5). In this case report, we start with a description of an AF ablation procedure where the persistent PV conduction could not be abolished with PV antral ablation, leading to identification of an IB, whose entry site at right atrium had to be ablated to achieve a durable PVI. Thereafter, we discuss the importance and differential diagnosis of persistent PV electrograms along with the necessity for confirming the position of the entrance and exit block in AF ablation.