Atrial fibrillation ablation: less is more?: Figure 1

This editorial refers to ‘A minimal or maximal ablation strategy to achieve pulmonary venin isolation for paroxysmal atrial fibrillation: a prospective multi-centre randomized controlled trial (the Minimax study)’†, by A.J.A. McLellan et al., on page 1812. Following the initial publication by Haïssaguerre et al. back in 1998 that described the focal origin of atrial fibrillation (AF) in the pulmonary veins (PVs) in some patients,1 a revolution in the field of AF therapy took place. From the very beginning and still nowadays, PV isolation has been the cornerstone of AF ablation. The first approach involved a limited segmental isolation of PVs. However, due to a relatively high recurrence rate, other ablation techniques have been developed, involving a PV antral isolation,2 often complemented by ablation lines, and ablation of complex fractionated electrograms. This ‘maximalist’ ablative approach was used by most groups over the past decade; however, the initial enthusiasm was tempered by a relatively high recurrence rate and the need for multiple ablation procedures, mainly in long-standing persistent AF. Furthermore, several randomized studies have produced conflicting results regarding the benefit of adding ablation lines, or complex fractionated atrial electrogram (CFAE) ablation.3–6 Other groups focused their attention on electrophysiological mechanisms, proposing rotor ablation7 or ablation of dominant frequency areas in order to ablate regions critical to maintenance of the arrhythmia;8 however, negative studies and lack of reproducibility of results have led to some scepticism. Even in the field of surgical AF ablation, doubts about the benefit of extensive lesions as opposed to PV isolation have been raised by a recent multicentre study that failed to demonstrate any benefit of the biatrial Maze procedure vs. PV isolation.9 So, where are we now in the field of AF ablation? Perhaps the major change in recent years has been the technical advances that allow the creation of better and more durable lesions. The advent of contact force measurement in radiofrequency catheters has clearly improved ablation outcomes.10 In parallel, new single-shot techniques, mainly cryoballoon therapy, also have proven highly effective.11 Other techniques such as laser ablation are being evaluated, amid claims about creating transmural and permanent lesions. It seems that with the introduction of these new technical advances, our previous knowledge in the field should be rethought and re-evaluated: one thing is the lesion we wanted to produce, and another is what we really achieve. In fact, most redo studies show a high number of gaps in PVs; therefore, the assumption that our procedures result in permanent PV isolation has been too optimistic. We are probably entering an era of minimalism in the field, reintroducing the concept that ‘less is more’—a phrase from a Robert Browning poem that was adopted by minimalist architect Mies Van de Rohe. The Minimax study12 results point in the same direction. The authors designed a multicentre study, with the hypothesis that what they call a ‘maximal’ PV isolation ablation strategy, involving individual isolation of each PV including the intravenous ridge, would result in fewer recurrences, as compared with the ‘minimal’ approach, encircling pairs of PVs and avoiding ablation of the intravenous ridge. The study had a rather unexpected result. On one hand, in an intention-to-treat analysis, there was no difference between the two approaches in ablation success during follow-up. However, as many as 44% of patients crossed from the minimal to maximal strategy. Therefore, the authors proved that PV isolation using the minimal approach (encircling pairs of PVs) was only achievable in 56% of the attempts. Furthermore, the ‘minimal approach’ subgroup that required crossover (ablation of the venous ridge) to achieve PV isolation did significantly worse, compared with those in whom PV isolation was achieved by the larger encircling alone. The authors conclude that applying the minimal strategy first was useful in selecting a subgroup of patients in whom a less extensive ablation would result in good results. In contrast, patients requiring venous ridge ablation had worse outcomes despite more extensive ablation, probably due to anatomical differences. Despite all the accumulated experience, we still lack enough information to personalize ablation in each individual, which could result in more efficacious and less extensive ablations in some patients. In each specific patient, a deeper knowledge of the extent of the atrial disease and the underlying pathophysiological mechanism is needed in order to apply an individualized procedure, based on the extension and distribution of fibrosis and the identification of triggers, or areas critical for re-entry. In addition, it would be desirable to avoid unnecessary procedures when chances of success are very low. Whether new mapping tools or detailed magnetic resonance imaging (MRI) may contribute to this objective is still an open question (Figure 1). Meanwhile, a ‘minimalist’ approach based on effective PV isolation seems advisable in most patients, reserving more extensive ablations for specific patients with very enlarged atria, extensive fibrosis, or long-standing persistent AF, recognizing that even in the best hands, the success rate in such patients will be limited. Posterior view of late gadolinium enhancement magnetic resonance imaging (MRI) merged with a CARTO® image of the left atrium. (A) In red, an area of late gadolinium enhancement in the posterior wall that corresponded to a low electrogram voltage area, suggesting localized fibrosis. The area was targeted during ablation (B) (personalized ablation). Conflict of interest: none declared.