Substrate modification by adding ablation of localized complex fractionated electrograms after stepwise linear ablation in persistent atrial fibrillation

Anatomical hotspots of fractionated electrograms in the left and right atrium: do they exist?

Aims

Targeting of complex fractionated electrograms (CFEs) in the atria is not yet beneficial in treating drug-refractory atrial fibrillation (AF). In order to gain insight into potential anatomical hotspots of fractionated electrograms, a structured literature search was performed.

Methods and results

PubMed was searched for studies describing fractionation during human atrial electrophysiological measurements (n = 565), of which 36 articles described the pre-ablation distribution of fractionated electrograms for the left atrium and/or right atrium in at least four regions. Fractionation was commonly found in high proportions within all regions of both atria, without clear preference for specific regions. Furthermore, no differences in the fractionation distribution between paroxysmal AF and persistent AF patients were observed.

Conclusion

Whereas atrial inhomogeneous conduction is widely believed to play a key role in AF initiation and perpetuation, different electrophysiological causes for fractionation and the influence of measurement properties complicate identification of the arrhythmogenic substrate. Thereby, simply targeting all CFEs would be short-sighted. Further research is warranted on how to distinguish 'physiologic CFEs' from 'pathologic CFEs', with only the latter reflecting potential targets for ablative therapy of AF.

Electrophysiological Perspectives on Hybrid Ablation of Atrial Fibrillation

To overcome limitations of minimally invasive surgical ablation as a standalone procedure in eliminating atrial fibrillation (AF), hybrid approaches incorporating adjunctive endovascular catheter ablation have been proposed in recent years. The endovascular component targets residual conduction gaps and identifies additional electrophysiological targets with the goal of minimizing recurrent atrial arrhythmia. We performed a systematic review of published studies of hybrid AF ablation, analyzing 432 pooled patients (19% paroxysmal, 29% persistent, 52% long-standing persistent) treated using three different approaches: A. bilateral thoracoscopy with bipolar radiofrequency (RF) clamp-based approach; B. right thoracoscopic suction monopolar RF catheter-based approach; and C. subxiphoid posterior pericardioscopic ("convergent") approach. Freedom from recurrence off antiarrhythmic medications at 12 months was seen in 88.1% [133/151] for A, 73.4% [47/64] for B, and 59.3% [80/135] for C, with no significant difference between paroxysmal (76.9%) and persistent/long-standing persistent AF (73.4%). Death and major surgical complications were reported in 8.5% with A, 0% with B and 8.6% with C. A critical appraisal of hybrid ablation is presented, drawing from experiences and insights published over the years on catheter ablation of AF, with a discussion of the rationale underlying hybrid ablation, its strengths and limitations, where it may have a unique role in clinical management of patients with AF, which questions remain unanswered and areas for further investigation.