Author + information
- Published online April 17, 2017.
- Francis Marchlinski, MD∗ ( and )
- Ramanan Kumareswaran, MD
- Cardiac Electrophysiology Section, Cardiovascular Division, Hospital of the University of Pennsylvania and University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
- ↵∗Address for correspondence:
Dr. Francis E. Marchlinski, Cardiac Electrophysiology, University of Pennsylvania Health System, 3400 Spruce Street, Founders 9 Pavilion, Philadelphia, Pennsylvania 19104.
Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice yet our understanding of this arrhythmia remains incomplete. Similar to any arrhythmia, AF requires a trigger to initiate and substrate that sustains it. Furthermore, there is considerable interest in identifying possible drivers in AF, whether it be rotors, focal sources, or small re-entrant circuits (1–5).
Most triggers for AF originate from pulmonary vein atrial muscle sleeves and therefore durable pulmonary vein isolation (PVI) has become the most important goal in any AF ablation strategy (1–3). This approach has achieved significant improvement in patients with paroxysmal AF (1). Yet success rates for PVI ablation in persistent AF still remain lower than in paroxysmal AF (2,3). Although it is still unclear whether patients with persistent AF are more resistant to effective PVI, various additional ablation strategies have been developed to target this patient population. These techniques address targeting additional non–pulmonary vein triggers, targeting drivers of AF such as rotors or substrate modification incorporating additional lines or isolating regions of scar or of the posterior wall (3–5).
Cut and sew surgical AF ablation in the form of the maze procedure produces good control of AF but requires extensive surgery and is associated with significant comorbidity (6). Radiofrequency (RF) and cryoablation has replaced the cut and sew technique for surgical ablation. Combining endocardial catheter ablation with epicardial surgical ablation as a hybrid option is also currently being evaluated for treatment of AF (7). Surgical techniques for AF ablation vary among studies and include epicardial isolation of pulmonary veins, additional lines including box isolation of posterior wall with roof and floor lines, ligament of Marshall ablation, autonomic denervation, or left atrial appendage exclusion. Evaluating the success rate of specific surgical ablation techniques is difficult because multiple approaches have been used and the number of patients used in each observational report has been small (6,7).
In this issue of JACC: Clinical Electrophysiology, Kress et al. (8) publish their sizeable experience of hybrid ablation and compare the results to their own institutional experience with endocardial catheter ablation for patients with persistent AF. It is a single-center, retrospective analysis of their clinical experience with AF ablation. Their surgical technique involved transabdominal endoscopic epicardial ablation of posterior wall using RF energy. The anterior left inferior pulmonary trunk was also isolated. A subgroup of patients received lesions between inferior vena cava and right inferior pulmonary vein. Endocardial ablation involved either cryoballoon or RF-guided PVI. Ablation of complex fractionated atrial electrograms or additional lines was delivered in most of the patients. The authors report based on their experience that the hybrid procedure has significantly fewer arrhythmia recurrence (37% vs. 58%), repeat ablation (9% vs. 26%), and greater AF free survival (72% vs. 51%). The outcome differences reported by the authors are impressive. However, this study does need closer scrutiny of the techniques, design, and analysis before drawing firm conclusions about superiority.
It is important to start by identifying differences in the study populations. More of the hybrid patient population (58%) has had prior ablation compared to only 25% of the endocardial ablation group. The interpretation by the authors that this possibly implies that the hybrid ablation group is a greater challenge may or may not be true. The success rate of ablation increases with repeated procedures as we “whittle away” (9). Furthermore, the percentage of patients whose veins were chronically reconnected at the time of the repeat procedure was not reported. It is relevant to consider this important influence given that the greatest benefit of AF ablation is achieved by durable PVI.
Differences in the study groups with respect to the endocardial techniques used and the targets or endpoints of ablation should also be noticed. Cryoballoon is a promising new technology for single-shot PVI and was used in the majority of the patients in this study (10). Of note, the effectiveness of this technology has yet to be studied in a randomized control fashion for persistent AF. Cryoballoon ablation was used in approximately 73% of patient population in both groups. Yet the larger and more effective Arctic Front Advance cryoballoon (Medtronic Inc., Minneapolis, Minnesota) was used in 67% of hybrid group versus 45% of endocardial-only group. In addition, posterior wall isolation can be performed endocardially with RF ablation. This was not tried in the endocardial catheter ablation–only group. If the goal of the surgical ablation was to isolate the posterior wall then this study does not address whether surgical ablation is superior to endocardial ablation when targeting posterior wall isolation. These differences in techniques and ablation targets in the patients undergoing the catheter based ablation in the report by Kress et al. (8) may have played a role in outcome differences noted.
Follow up in both groups of patients reported by Kress et al. (8) were also different. The average follow up was significantly longer in the endocardial ablation group, mean follow up of 13 versus 23 months. Ambulatory monitoring was done in 32% of endocardial ablation group compared to only 16% of hybrid group. More electrocardiography monitoring and longer duration increases the chance of diagnosing arrhythmia recurrence in the endocardial catheter ablation only group.
Thus, although the superiority in outcome with respect to fewer arrhythmia recurrences, need for repeat ablation and AF free survival was unequivocal and favored the hybrid procedure, it is possible these differences were at least exaggerated by differences in methodology that make it impossible at this point to attribute benefit with the hybrid surgical or endocardial catheter ablation approach to the addition of the surgical component. Certainly the effectiveness of catheter based RF techniques have been recently enhanced by contact force technology and whether more antral vein isolation and effective catheter-based posterior wall isolation using contact force equipped catheters could have produced similar or even superior outcome certainly needs to be considered a real possibility (11,12).
What adds to our caution are the data related to the abolition of symptoms and the reported complications noticed. Patients generally undergo treatment for AF to alleviate symptoms and to improve quality of life. Despite undergoing a more invasive procedure, there was no clear benefit in terms of symptom improvement between groups. Admittedly, this study was not powered adequately to compare complications between strategies. These procedures were done at a single center with relatively high hybrid ablation volume. Nevertheless, it is noteworthy that 7.8% of patients experienced a complication during the hybrid ablation procedure including 1 stroke and 1 death. This also highlights the importance of properly assessing not only benefits but also risks before widely adopting more invasive strategies despite improved arrhythmia control as reported.
The investigators need to be congratulated for highlighting the feasibility of a hybrid approach to address persistent AF and their overall good outcomes. However, the story is incompletely told. Understanding the electrophysiological mechanism of benefit of each surgical ablation technique will allow us to create the best possible approach for long-term AF control. We need to better identify the effective techniques that require a surgical approach and cannot be done by less invasive endocardial catheter ablation. We need a prospective comparison of more similarly matched approaches. Perhaps we are closer but more work is required before wider adaptation of the hybrid technique is recommended as the “best approach” for patients with persistent AF.
↵∗ Editorials published in JACC: Clinical Electrophysiology reflect the views of the authors and do not necessarily represent the views of JACC: Clinical Electrophysiology or the American College of Cardiology.
Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- 2017 American College of Cardiology Foundation
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