How to ablate idiopathic ventricular arrhythmias difficult to map and access the origins of arrhythmias

The major sites of idiopathic ventricular arrhythmia (IVA) origins have been increasingly elucidated over the past two decades. Catheter ablation of IVAs is usually very successful. However, it remains challenging when they arise from some specific anatomical structures such as the papillary muscles, left ventricular (LV) summit, cardiac crux, etc. The major challenge of the catheter ablation of those IVAs should be a difficult access to the ablation target. For IVAs originating from thick muscle bands such as the papillary muscles, it should be challenging to obtain stable contact of the ablation catheter on the muscle bands, and also to create a deeper lesion to reach IVA foci deep inside the muscle bands. For IVAs originating from epicardial foci in the LV summit and cardiac crux, transpericardial and transvenous approaches should be used appropriately. Anatomical obstacles such as a thick epicardial fat pad and close proximity to the coronary arteries may preclude an epicardial catheter ablation due to a high impedance and unsatisfactory lesion formation, and the risk of collateral damage, respectively. IVAs originating from intramural foci should require deeper lesion for a successful ablation. Radiofrequency catheter ablation by an anatomical approach from a site remote from IVA foci can be considered when that by a direct approach is not available due to an anatomical barrier. Cryoablation may be an option to resolve an unstable contact, high impedance, and collateral damage. Bipolar and simultaneous unipolar radiofrequency catheter ablation may be considered to create a deeper lesion. Transcoronary and transvenous alcohol ablation may be an option to treat IVAs refractory to catheter ablation. In this symposium, useful and effective treatments of such challenging IVAs will be discussed.