Catheter Ablation of Atrial Fibrillation: Do the Newer Tools Help?

Atrial fibrillation (AF) is the most prevalent sustained cardiac arrhythmia, increasing in occurrence with age. Based on recent epidemiology, it is estimated to affect 6.1 million Americans, and this number is likely to increase to 15.9 million by 2050.¹ Partly because of the limitations of antiarrhythmic medications, catheter ablation has come into common use for clinical treatment of atrial fibrillation. Due to considerable improvements in efficacy and safety, catheter ablation is considered a second-line treatment in the ACC/AHA/ESC clinical guidelines.² According to the HRS/EHRA/ECAS Expert Consensus Statement, pulmonary vein isolation (PVI) is the cornerstone of most catheter ablation procedures to treat AF.³ Other proposed targets for ablation include complex fractionated atrial electrograms (CFAE), which reflect structural and functional properties of the atrial myocardium during AF. Multielectrode catheter technology, even in earlier versions, held promise in delivering contiguous lesions and shortening procedure times.^4,5 It also has the potential to deliver more contiguous lesions and cause less unnecessary damage to atrial tissue. The ability to map and ablate through the same electrodes should simplify and shorten the procedure.

In this issue of the Journal of Invasive Cardiology, Zeb et al report a single-center experience with the Medtronic Ablation Frontiers tool kit.⁶ The details on the use of the associated multichannel RF ablation generator are described. In the study, 60% of the patients underwent PVI alone. The success rate (sinus rhythm without antiarrhythmic medications) in paroxysmal AF was 64% with one or more procedures, and 45% in persistent AF with one or more procedures. Success was primarily determined by 12-lead electrocardiogram and clinical assessment at 3–6 month follow-up. All patients remained on antiarrhythmic medications for 6 weeks after ablation. The procedure-related complication rate was 11%. Pulmonary vein stenosis, which is largely eliminated by current techniques, occurred in 1 patient.

Although other published studies of AF ablation have reported higher success rates, this study offers “real world” numbers that are likely to be reproduced at other centers. It is possible that with routine extended monitoring, the longer-term success rates in these patients could be lower. The authors found that lesions delivered by the pulmonary vein ablation catheter (PVAC) were beneficial, whereas the additional CFAE lesions delivered by the multi-array septal catheter (MASC) and multi-array ablation catheter (MAAC) did not improve outcomes, and may have produced less favorable results. The lack of benefit from CFAE ablation in this study may be due to patient selection bias, as the authors surmise, or could possibly be due to the ineffectiveness of these strategies and/or tools employed to achieve them.

In the United States, the most common method of performing pulmonary vein isolation involves the delivery of point-by-point lesions using an irrigated tip catheter.⁷ Cryoballoon catheter ablation is a promising modality being employed in a limited number of centers, with the expectation of shorter procedure times. The mapping of dominant frequencies is also being explored as a way to enhance the efficacy of AF ablation.⁸ Technologies such as Stereotaxis and the Hansen Sensei add remote navigation capabilities, which are also being employed to various degrees in AF ablation procedures.

This study adds to prior evidence that multielectrode catheter technology, here in the form of the PVAC catheter, can be an effective tool with which to accomplish AF ablation. Although the manufacturer provides two additional catheters to address targets other than the pulmonary vein triggers, this study among others raises questions about the value of those additional tools and lesions. As shown in multiple studies, effective pulmonary vein isolation is often the key to a successful procedure. The use of multielectrode catheter technology appeared to shorten procedure and fluoroscopy times. Since this was not a comparative study, the efficacy of a PVAC ablation compared to a single-tip catheter ablation was not evaluated.

As we learn more about AF pathophysiology and appropriate ablation targets, an array of tools is becoming available for use in catheter ablation procedures. Most tools are associated with an appreciable learning curve. The pros and cons of the various technologies should be critically evaluated in single- and multi-center studies, to develop successful strategies to improve the efficacy and safety of these procedures. It is in that context that the present study should be evaluated.

Catheter ablation of atrial fibrillation remains a significant clinical challenge in cardiac electrophysiology today. The achievement of still higher success rates in AF ablation in the future will likely require a more advanced understanding of AF mechanisms, which will allow some individualization of the ablation procedure for each patient. Technological advances that make AF ablation quicker and easier are welcome.

References

1. Myasaka Y, Barnes ME, Gersh BJ, et al. Secular trends in incidence of atrial fibrillation in Olmsted County, Minnesota, 1980 to 2000, and implications on the projections for future prevalence. Circulation. 2006;114(2):119-125.
2. Fuster V, Ryden LE, Cannom DS, et al. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation — executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. 2006;114(7);E257-E354; originally published online Aug 2, 2006; DOI:10.1161/CIRCULATIONAHA.106.177031.
3. Calkins H, Brugada J, Packer DL, et al. HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for personnel, policy, procedures, and follow-up. Heart Rhythm. 2007;4(6):816-861. Epub 2007 April 30.
4. Kocheril AG. Right atrial mapping and linear ablation for paroxysmal atrial fibrillation. J Intervent Card Electrophysiol. 2001;5(4):505-510.
5. Kocheril AG, Calkins H, Sharma AD, Cher D, Stubbs HA, Block JE. Hybrid therapy with right atrial catheter ablation and previously ineffective antiarrhythmic drugs for the management of atrial fibrillation. J Interv Card Electrophysiol. 2005;12(3):189-197.
6. Zeb M, Yue A, Scott P, et al. Single center experience of catheter ablation for atrial fibrillation using multi-electrode mapping and ablation catheters. J Invasive Cardiol. 2011;23(10):407-413.
7. Wilber DJ, Pappone C, Neuzil P, et al; ThermoCool AF Trial Investigators. Comparison of antiarrhythmic drug therapy and radiofrequency catheter ablation in patients with paroxysmal atrial fibrillation: a randomized controlled trial. JAMA. 2010;303(4):333-340.
8. Latchamsetty R, Kocheril AG. Review of dominant frequency analysis in atrial fibrillation. JAFIB. 2009;1(9):551.

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From the Christie Clinic, Provena Covenant Medical Center, and the University of Illinois, Urbana-Champaign, Illinois.
Disclosure: The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. No conflicts of interest were reported regarding the content herein.
Address for correspondence: Abraham G. Kocheril, MD, FACC, FACP, FHRS, Christie Clinic Cardiology, 101 West University Ave., Champaign, IL 61820. Email: kocheril@illinois.edu