Dechanneling Left Atrial Late Gadolinium Enhancement.

Beginning with initial reports of catheter ablation with high-energy direct current shocks for focal and simple arrhythmias in the early 1980s,1 catheter ablation technology and our understanding of arrhythmia mechanisms have rapidly evolved. The identification of left atrial muscular extensions in the pulmonary veins (PVs) by Haïssaguerre et al2 in 1998 opened the era of catheter ablation for suppression of atrial fibrillation (AF). The initial strategy of focal PV trigger ablation was limited by the variability in induction and mapping of the foci, as well as PV stenoses after ablation deep in the veins. To eliminate the need for identification and ablation of individual foci deep in the PVs, ostial isolation of the PV was pursued. Over time, this approach has evolved to an antral PV isolation technique resulting in wide-area circumferential ablation, which mitigates the likelihood of PV stenosis, includes more potential triggers within the isolation zone, and is more likely to modify periatrial autonomic inputs. With wide-area circumferential ablation, however, the ablation circumference has increased, thus increasing the potential for inadvertent gaps in ablation lesions. In addition, strategies such as linear ablation have been implemented in difficult cases, thus adding to the possibility that gaps may exist, and paths for initiation and maintenance of fixed reentry may be created after the procedure. The observation of reentrant atrial tachycardia (AT) after AF ablation is therefore not only related to the burden of de novo scar but also the presence of gaps in linear lesions or wide-area circumferential ablation. Approximately two thirds of post-AF ablation patients with an AT immediately after their ablation will have persistent AT after the healing period. Entrainment mapping strategies can be successfully applied to identify and target these circuits.3 Cardiac imaging with computed tomography or cardiac magnetic resonance (CMR) has long been implemented for creation of 3-dimensional segmentations for enhanced procedural guidance. Most commonly, this approach can be used to tailor lesion delivery to individual variations in left atrial geometry and PV anatomy. In 2007, a study from Peters et al4 suggested that late gadolinium enhancement (LGE) CMR could visualize left atrial lesions after PV isolation. LGE CMR was later championed by Marrouche et al5 to enhance the stratification of potential candidates for AF ablation. In this issue of Circulation: Arrhythmia and Electrophysiology, Fochler et al6 describe LGE CMR-based dechanneling as a strategy to treat reentrant AT after AF ablation. They report a retrospective analysis of 102 patients who underwent EP study and mapping after an initial AF ablation with CMR before each ablation. The authors confirm that a strategy of left atrial linear lesion sets at the index procedure associated with AT after ablation. Of 102 patients, 46 presented with AF only EDITORIAL