Demonstration that the myocardial sleeves of the pulmonary veins (PVs) are the main triggering and maintaining foci for paroxysmal atrial fibrillation (AF) have stimulated studies investigating electrophysiological properties of PVs and the adjacent left atrial (LA) myocardium. It has been shown that PV myocytes have a shorter action potential duration and are more prone to effects of local autonomic nerve stimulation in terms of shortening of action potential duration, early after depolarization formation and triggered firing compared to left atrial myocytes (1). The intrinsic cardiac autonomic nervous system (ICANS) forms clusters of neurons called ganglionic plexi (GPs), and studies using histologic examination of heart sections have shown that these GPs are localized preferentially at certain epicardial sites adjacent to the left and right atria (2). The precise role of ICANS in AF continues to be an area of intense research (3), and matters are not helped by the uncertainty regarding the best way to identify and target ICANS peri-procedurally. As there can be significant variability of GP sites in individual patients, endocardial high-frequency stimulation (HFS) has been used to aid their localization in the electrophysiology laboratory (4).