Electro-anatomic mapping systems in arrhythmias.

Electroanatomic mapping systems have permitted and facilitated difficult interventional ablation procedures for more than a decade. Initially, their use has been in arrhythmias in which the ablation target is difficult to identify, such as ventricular tachycardias in structural heart disease, atypical atrial flutters, or arrhythmias in patients with complex congenital heart defects. In the recent years, electroanatomic mapping systems have also been used to guide catheter-based isolation of the pulmonary veins, an important component of the modern management of atrial fibrillation (AF). Electroanatomic mapping systems integrate three important functionalities, namely (i) non-fluoroscopic localization of electrophysiological catheters in three-dimensional (3D) space; (ii) analysis and 3D display of activation sequences computed from local or calculated electrograms, and 3D display of electrogram voltage ('scar tissue'); and (iii) integration of this 'electroanatomic' information with non-invasive images of the heart (mainly computed tomography or magnetic resonance images). Although better understanding and ablation of complex arrhythmias mostly relies on the 3D integration of catheter localization and electrogram-based information to illustrate re-entrant circuits or areas of focal initiation of arrhythmias, the use of electroanatomic mapping systems in AF is currently based on integration of anatomic images of the left atrium and non-fluoroscopic visualization of the ablation catheter. Their use in the treatment of AF is mainly driven by safety considerations such as shorter fluoroscopy and procedure times, or visualization of cardiac (pulmonary veins) and extra-cardiac (oesophagus) structures that need to be protected during the procedure. In the future, the use of magnetic resonance images, and potentially of high-quality 3D ultrasound images, could provide anatomic information without ionizing radiation and may be helpful to visualize left atrial scar tissue.