Extreme bradycardia during pulmonary vein isolation: keep on ablating in that region?

The role of the tripartite synapse in the heart: how glial cells may contribute to the physiology and pathophysiology of the intracardiac nervous system

One of the major roles of the intracardiac nervous system (ICNS) is to act as the final site of signal integration for efferent information destined for the myocardium to enable local control of heart rate and rhythm. Multiple subtypes of neurons exist in the ICNS where they are organized into clusters termed ganglionated plexi (GP). The majority of cells in the ICNS are actually glial cells; however, despite this, ICNS glial cells have received little attention to date. In the central nervous system, where glial cell function has been widely studied, glia are no longer viewed simply as supportive cells but rather have been shown to play an active role in modulating neuronal excitability and synaptic plasticity. Pioneering studies have demonstrated that in addition to glia within the brain stem, glial cells within multiple autonomic ganglia in the peripheral nervous system, including the ICNS, can also act to modulate cardiovascular function. Clinically, patients with atrial fibrillation (AF) undergoing catheter ablation show high plasma levels of S100B, a protein produced by cardiac glial cells, correlated with decreased AF recurrence. Interestingly, S100B also alters GP neuron excitability and neurite outgrowth in the ICNS. These studies highlight the importance of understanding how glial cells can affect the heart by modulating GP neuron activity or synaptic inputs. Here, we review studies investigating glia both in the central and peripheral nervous systems to discuss the potential role of glia in controlling cardiac function in health and disease, paying particular attention to the glial cells of the ICNS.

Sudden asystole during radiofrequency ablation: a case report and literature review

BACKGROUND

Radiofrequency (RF) ablation is a widely accepted and ideal therapeutic tool to cure some tachycardias. The occurrence of complications varies depending on the procedure being performed. Sudden unexpected prolonged asystole is rare for most ablation procedures and the underlying mechanisms remain unclear.

CASE PRESENTATION

A case of sudden prolonged asystole induced by RF ablation of a concealed left free wall accessory in a 59-year-old woman with recurrent tachycardia. RF application provoked progressive slowing of the sinus rhythm and then a 13.2-second period of asystole ensued. Asystole was self-healing and no complications were seen in the following follow-up.

CONCLUSIONS

RF ablation may develop prolonged asystole due to vagus response caused by stimulation of unmyelinated vagal C-fibers or ganglionated plexus (GP). Reflexible asystole is reproducible and resolves independently, without affecting the procedure of RF ablation.