Despite major advances in techniques and technology over the past 15 years, the clinical outcomes for catheter ablation in non-paroxysmal atrial fibrillation patients remain disappointing, write Tom Wong and Shouvik Haldar (London, UK). The authors review data which favour a hybrid and/or a surgical approach for this set of patients.
Catheter ablation
Since the seminal paper of Haïssaguerre describing the importance of pulmonary vein ectopics in triggering atrial fibrillation (AF), catheter based percutaneous ablation has grown exponentially worldwide to treat this epidemic condition.1 In the last fifteen years, we have witnessed an evolution of mapping technologies at a tremendous pace from two dimensional radiography to sophisticated three dimensional mapping systems.2,3
In tandem, there have been significant advances in catheter related technologies in an effort to improve outcomes in AF ablation, including the advent of irrigated-tip catheters to improve lesion depth and size, the use of steerable sheaths to help maintain better contact between catheter tip-tissue, tissue contact force sensing to reduce acute pulmonary vein reconnections, novel navigations and so on.4-7
Although contemporary catheter ablation can provide excellent results in paroxysmal AF, the clinical outcome in ablating non-paroxysmal AF remains disappointing, with patients often needing multiple procedures.8,9
Surgical ablation
It is important to appreciate the fact that the first breakthrough in the interventional management of AF was the Cox-Maze surgical procedure, first reported in 1987.10 The procedure involved making multiple atrial incisions to create a series of scars resulting in atrial compartmentalisation and isolation of the posterior left atrium and all four pulmonary veins and was based mechanistically upon Moe’s multiple wavelet hypothesis.11 These scars also interrupted the macro-re-entrant circuits required by the atrial tissue to maintain AF, thus modifying the atrial substrate. The long-term follow-up results were exceptional, with sinus rhythm maintained in 96% of patients beyond five years.12 The Cox-Maze procedure became the gold standard for surgical ablation but the multiple atrial incisions and cardiopulmonary bypass ensured that the procedure remained long, technically complex with significant morbidity. Although highly effective, the Cox-Maze failed to gain popularity as a treatment modality for standalone AF, and became reserved for those undergoing concomitant cardiac surgery.
Recent advances have seen the emergence of minimally invasive surgical techniques using energy delivering ablation devices in lieu of the atrial incisions to create radiofrequency lesions. Early ‘minimally invasive’ reports still used muscle splitting, mini-thoracotomy incisions for instrumentation. Efforts to reduce patient morbidity and discomfort, and to facilitate a faster post-operative recovery led to the totally thoracoscopic approach first reported in 2008 ie. without muscle splitting mini-thoracotomies or additional incisions. Access in these cases was via three thoracoscopic access ports bilaterally (one 10mm and two 5mm).13 This totally thorocoscopic technique was used in the first randomised controlled trial reported in 2011—the FAST (Atrial fibrillation catheter ablation versus surgical ablation treatment) study—comparing catheter ablation with surgical ablation in 124 patients with drug-refractory AF.14 The patients were a mix of paroxysmal and non-paroxysmal AF with the primary endpoint of freedom from left atrial arrhythmia at 12 months, off antiarrhythmic drugs. The surgical ablation group results were superior with 65% vs. 36% success rate at one year. However, this was offset by a significantly higher adverse event rate in surgical ablation as compared to the catheter ablation group (34.4% vs. 15.9%; p=0.027).
Ablation studies studying non-paroxysmal forms of AF such as long-standing persistent AF alone are limited and these patients fare the worst in terms of clinical outcomes from catheter ablation. Our group has compared catheter ablation vs. totally thoracoscopic surgical ablation in this subset of patients and results (unpublished data) have again been encouraging for surgical ablation with 69% freedom from left atrial arrhythmia at 12 months vs. 36% for catheter ablation after a single procedure. Major complications mirrored that seen in the FAST study with 30% in surgical ablation vs. 8% in catheter ablation.
Hybrid AF ablation
In 2012, the first ‘hybrid’ totally thoracoscopic surgical ablation and transvenous endocardial catheter ablation was reported in a single-centre prospective study consisting of 26 patients (46% persistent).15 The results were impressive with 12-month success off antiarrhythmic drugs of 93% for paroxysmal AF and 90% for persistent AF and, in contrast to the FAST study, no significant complications were reported. The rationale for this approach stems from the fact that some ablation lesions that are part of the Cox-Maze lesion set cannot be accomplished using a totally thorocoscopic surgical approach. The high success rates in this trial demonstrate the potential of hybrid strategies, which combine the advantages and simultaneously limit the shortcomings of each individual technique.
Finally, an alternative hybrid approach has also shown great promise. The convergent technique combines epicardial ablation performed via transdiaphragmatic access (ie. without chest incisions, thoracoscopic ports, lung deflation, or tissue dissection) with endocardial ablation.16 Fifty patients with non-paroxysmal AF were treated in a non-randomised single-centre study. Implantable loop recorders were used for follow-up arrhythmia detection and sinus rhythm maintenance at 12 months was 88% and at 24 months was 87%. These success rates are extremely high for non-paroxysmal AF patients and although the complication rate (10%) was higher than that expected with catheter ablation alone it was still significantly less than that observed in the FAST study using the totally thoracoscopic approach.
Future directions
Despite major advances in techniques and technology over the past 15 years, the clinical outcomes for catheter ablation in non-paroxysmal AF remain disappointing. Thorocoscopic or transdiaphragmatic, epicardial surgical ablation techniques on a beating heart and/or hybrid epi/endocardial ablation have shown promising results and although surgical ablation techniques appear to have higher complication rates these are likely to fall as experience grows with these procedures. Larger scale randomised controlled trials are underway to evaluate totally thoracoscopic and hybrid ablation modalities in more detail and to delineate their role in the management of AF (Prospective, randomized comparison of hybrid ablation vs. catheter ablation NCT02344394 and Hybrid versus catheter ablation in persistent AF NCT02441738. This includes an ongoing RCT from our group comparing in detail catheter ablation with surgical ablation in long-standing persistent atrial fibrillation including clinical outcomes, quality of life and cost-effectiveness analysis (Catheter versus thoracoscopic surgical ablation in long standing persistent atrial fibrillation ISRCTN18250790). In particular, in those patients with non-paroxysmal AF, this progress perhaps should not be viewed as a threat to electrophysiologists as the treatment of these advanced substrates may well be best served with a multidisciplinary approach, combining the expertise of cardiac surgeons and electrophysiologists, which can only be of benefit to our patients.
References
- Haissaguerre M, Jais P, Shah D, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998; 339:659–66
- Nakagawa H, Ikeda A, Sharma T, et al. Rapid high resolution electroanatomical mapping: Evaluation of a new system in a canine atrial linear lesion model. Circ Arrhythm Electrophysiol 2012; 5:417–24
- Mantziari L, Butcher C, Kontogeorgis A, et al. The utility of a novel rapid high-resolution mapping system in the catheter ablation of arrhythmias—an initial human experience of mapping the atria and the left ventricle. JACC Clin Electrophysiol 2015; 5:411–420
- Haldar S, Jarman J, Panikker S, et al. Contact force sensing technology identifies sites of inadequate contact and reduces acute pulmonary vein reconnection: A prospective case control study. Int J Cardiol 2013; 168:1160–6
- Ullah W, Hunter R, Haldar S, et al. Comparison of robotic and manual persistent AF ablation using catheter contact force sensing an international multicenter registry study. Pacing Clin Electrophysiol 2014; 37:1427–1435
- Jarman J, Panikker S, Das M, et al. Relationship between contact force sensing technology and medium term outcome of atrial fibrillation ablation: A multicenter study of 600 patients. J Cardiovasc Electrophysiol 2014 Dec 27. doi: 10.1111/jce.12606
- Reddy VY, Shah D, Kautzner J, et al. The relationship between contact force and clinical outcome during radiofrequency catheter ablation of atrial fibrillation in the TOCCATA study. Heart Rhythm 2012; 9:1789–95
- Rostock T, Salukhe TV, Steven D, et al. Long-term single- and multiple-procedure outcome and predictors of success after catheter ablation for persistent atrial fibrillation. Heart Rhythm 2011; 8:1391–7
- McCready JW, Smedley T, Lambiase PD, et al. Predictors of recurrence following radiofrequency ablation for persistent atrial fibrillation. Europace 2011; 13:355–61
- Cox JL, Boineau JP, Schuessler RB, et al. Modification of the maze procedure for atrial flutter and atrial fibrillation. J Thorac Cardiovasc Surg 1995; 110:473–84
- Moe G, Rheinboldt W, Abildskov JA. A computer model of atrial fibrillation. Am Heart J 1964; 67:200–20
- Prasad SM, Maniar HS, Camillo CJ, et al. The Cox maze III procedure for atrial fibrillation: long-term efficacy in patients undergoing lone versus concomitant procedures. J Thoracic Cardiovasc Surg 2003; 126:1822–8
- Yilmaz A, Van Putte BP, Van Boven WJ. Completely thoracoscopic bilateral pulmonary vein isolation and left atrial appendage exclusion for atrial fibrillation. J Thorac Cardiovasc Surg 2008; 136:521–2
- Boersma LVA, Castella M, van Boven W, et al. Atrial fibrillation catheter ablation versus surgical ablation treatment (FAST): A 2-center randomized clinical trial. Circulation 2012; 125:23–30
- Pison L, La Meir M, van Opstal J, et al. Hybrid thoracoscopic surgical and transvenous catheter ablation of atrial fibrillation. J Am Coll Cardiol 2012; 60:54–61
- Gersak B, Pernat A, Robic B, et al. Low rate of atrial fibrillation recurrence verified by implantable loop recorder monitoring following a convergent epicardial and endocardial ablation of atrial fibrillation. J Cardiovasc Electrophysiol 2012; 23:1059–66
Tom Wong and Shouvik Haldar are from the Royal Brompton and Harefield Hospitals, London, UK
