ABC | Volume 114, Nº4, April 2020

Original Article Correia et al. CA lesions and AF recurrence - a meta-analysis Arq Bras Cardiol. 2020; 114(4):627-635 Table 2 – Characteristics of the included studies and main findings Study, year Ablation method Ablation strategy Catheter used Time of LGE-MRI Main Findings McGann et al., 2008 9 RFCA PVI in addition to LA posterior wall and septal debulking. Externally irrigated ablation catheter 3 months after ablation Patients with scar ratios > 13% are 18.5 times more likely to have a favorable outcome and freedom from AF at 3 months Peters et al., 2009 10 RFCA PVI without routine addition of empiric ablation lines in the LA. 8-mm standard tip: N = 29 (83%); 3.5-mm externally irrigated tip ablation catheter: N = 6 (17%) 46 ± 28 days after ablation AF recurrence during the first year is associated with a lesser degree of PV and LA scarring after ablation Badger et al., 2010 11 RFCA PVA isolation with posterior wall and septal debulking 3.5-mm Thermocool irrigated tip ablation catheter 3 months after ablation Patients with successful AF termination had higher average total LA wall scar after ablation of 16.4 ± 9.8% (p = 0.004) and percent PVA scar of 66.2 ± 25.4 (p = 0.01) Akoum et al., 2011 12 RFCA PVI in a circular fashion in the PVAand additional debulking in LAposterior wall and septum 10-pole circular mapping catheter: N = NR; 3.5 mm Thermocool ablation catheter: N = NR 3 months after ablation Overall post-ablation LA wall scarring predicts recurrence in moderate fibrosis stages McGann et al., 2011 13 RFCA PVI in addition to posterior wall and septal debulking 3.5-mm Thermocool ablation catheter Immediately following ablation and 3 months after ablation At 1-year follow-up, patients with moderate scar formation 3 months after ablation had no AF recurrence. In comparison, all recurrences occurred in patients with mild scar formation 3 months after ablation (p = 0.02). Hunter et al., 2013 16 RFCA and cryoballoon ablation PVI by WACA or ostial ablation with a cryoballoon 3.5-mm irrigated ablation catheter: N = NR For cryoballoon ablation an 11F FlexCath sheath delivered a 23- or 28-mm cryoablation balloon: N = NR Pre-ablation and 3 months after ablation The proportion of patients free fromAF was unaffected by whether ablation lesions could be identified on imaging: 16 of 30 patients (53%) with ablation lesions identified remained free fromAF compared to 13 of 20 patients (65%) with no lesions identified (p = 0.560). Akoum et al., 2015 14 RFCA and cryoballoon ablation PVI with CFAE ablation, linear ablation lines of the CTI, and other ablations in the LA (roof line, mitral isthmus line, posterior wall) Cryo-balloon: N = 12 (6.7 %); Multi-electrode duty-cycled phased radiofrequency ablation: N = 8 (4.5 %); Nonirrigated and open- irrigation radiofrequency catheters: N = 157 (88.7 %) 3 months after ablation The more scarring overlaps fibrosis, the better the arrhythmia-free survival Parmar et al., 2015 15 RFCA PVI and additional debulking of the LA posterior wall 3.5-mm ablation catheter 3 months after ablation Poor scar formation on LGE-MRI was associated with higher rates of AF recurrence AF: atrial fibrillation; CFAE: complex fractionated atrial electrogram; CTI: cavotricuspid isthmus; LA: left atrium; LGE-MRI: Late gadolinium enhanced magnetic resonance imaging; NR: not reported; PV: pulmonary vein; PVA: pulmonary vein antrum; PVI: pulmonary vein isolation; RFCA: radiofrequency catheter ablation; WACA: wide area circumferential radiofrequency ablation injuries, strategies, such as reducing power in the posterior LA wall, monitoring temperature in the esophagus, irrigating the esophagus with cold water, and pre-procedural imaging, should be adopted. 31-33 Reproducibility A previous study by Chubb et al., 34 which investigated post-ablation atrial scar, using LGE-MRI, in 40 subjects undergoing first time ablation for AF, showed that post-ablation visualization of induced scars in the LA is reproducible. Moreover, they concluded that imaging should be performed at least 20 minutes after administration of gadolinium-based contrast for better reproducibility. 34 However, the study by Hunter et al. analyzed in the present review, which included 50 patients, concluded that LGE imaging of atrial scar is not yet sufficiently accurate to identify ablation lesions or determine lesion distribution reliably. A published consensus by the European Heart Rhythm Association stated that there is still neither recommendation nor expert consensus on the role of LGE-MRI to assist AF ablation procedures. The consensus, nevertheless, states that the available data are intriguing enough to warrant further research. 35 STAR AF II and DECAAF II Although previous studies have demonstrated the positive impact of targeting ablation strategies beyond circumferential pulmonary vein isolation (CPVI), the STAR AF II trial showed a different scenario. 23,36 The STAR AF II was a randomized 631