Intramural Ventricular Arrhythmias: How to Crack a Hard Nut.

Purpose of the review: Successful catheter ablation of ventricular arrhythmias depends on identifying the critical tissues that sustain the arrhythmia. Increasingly, the intramural space is being recognized as an important source of idiopathic and reentrant ventricular arrhythmias, representing a common cause of ablation failure. A systematic approach to mapping and ablating these arrhythmias is key to optimize outcomes.

Recent findings: Intramural ventricular arrhythmias are common in certain anatomical locations such as the left ventricular ostium or the interventricular septum. In these cases, mapping of the septal coronary veins provides an opportunity to explore the intramural compartment of the septum to perform activation mapping, entrainment and/or pace mapping. When an intramural arrhythmia is identified, ablation may require radiofrequency application from multiple sites, prolonged lesions, or special ablation techniques such as bipolar ablation or transvenous ethanol injection. Identification of intramural ventricular arrhythmias depends on comprehensive mapping that should include the coronary venous system, and ablation often requires advanced techniques. This paper provides a guide on when to suspect an intramural ventricular arrhythmia in the electrophysiology laboratory and how to approach mapping and ablation in these challenging cases.