Featuring AF Section Editor Insights

DOI: 10.19102/icrm.2011.020607

John Day, MD, FHRS, FACC
Editor-in-Chief

T. Jared Bunch, MD
Atrial Fibrillation Section Editor

Editor-in-Chief

Dear Readers,

I am pleased that this month's installment of my Editor-in-Chief's letter incorporates the perspectives of our Atrial Fibrillation Section Editor, Dr. T. Jared Bunch, whose expert insights related to AF are truly enlightening. Within this month's letter we would like to focus the commentary on a late-breaking study presented at the Annual Sessions of the Heart Rhythm Society on May 5, 2011. This study, Conventional Ablation for Atrial Fibrillation With or Without Focal Impulse and Rotor Modulation (the Confirm Trial), presented by Dr. Sanjiv Narayan and colleagues, could potentially represent a paradigm shift in our understanding and ablative treatment approach of persistent atrial fibrillation (AF). This study could also dramatically impact AF management, similar to the effect of pulmonary vein isolation (PVI) more than a decade ago.

For those that treat symptomatic persistent AF, maintenance of sinus rhythm with either a pharmacologic or ablative approach is often is a frustrating experience, particularly if the goal is to maintain sinus rhythm long-term. From an ablative strategy, we have long known that PVI is just “not enough” and long-term success rates of PVI in persistent AF have generally been disappointing. To overcome this obstacle some have suggested ablation of complex fractionated atrial electrograms (CFAE), for which reproducibility has proven to be a significant challenge, or multiple ablation lines in addition to pulmonary vein isolation. Unfortunately neither of these approaches has led to a dramatic improvement in the long-term maintenance of sinus rhythm.

Dr. Michel Haissaguerre^1–2 and colleagues from Bordeaux, France have suggested a step-wise ablation approach to these patients, which typically involves very long cases with extensive ablation until the AF can be converted to an atrial tachycardia. The atrial tachycardia can then be mapped and the patient can be ablated back to sinus rhythm. While success with this approach is improved, it is just not practical for the typical lab and operator. Moreover, one must question whether more atrial tissue is ablated in this approach than is necessary to maintain sinus rhythm as well as the long-term issues of future atrial tachycardias/flutters, decreased atrial transport function, and potentially increased fluoroscopy exposure following such an extensive ablation approach.

The primary premise of Dr. Narayan and colleagues is that in addition to the pulmonary veins, AF is driven by rotors which can be mapped, and when ablated, convert the patient to sinus rhythm with successful maintenance shown at 2 years. One could certainly ask, what is the basis for this rotor hypothesis of AF?

The initial work by Kalifa et al,³ in a healthy sheep model, noted that stable rotors arose from the posterior left atrium during AF that were characteristically the fastest and most stable electrical frequency. As the wavefronts spread from these stable rotors they became fragmented due to heterogeneity of front propagation velocity.

In a subsequent canine model of AF from pacing-induced heart failure, three patterns of rotors were observed; one rotor from the pulmonary veins, multi-site rotors with distinct frequencies typically arising near the pulmonary veins, and one in which there is a bi-atrial irregular activation without a clear driving rotor.⁴ This study confirmed that stable high frequency rotors drove AF but showed variance in locating, a finding that may reflect the model in which the AF was derived from a cardiomyopathy.

From these two studies we can conclude that there appears to be evidence to support stable rotors as drivers for AF, in most, but not all animals. In addition, these rotors tend to arise from areas often targeted indirectly by catheter ablation and MAZE procedures and as such may explain procedural success.

In the CONFIRM Trial, Dr. Narayan and colleagues enrolled 103 patients with a mean age of 62 (69% persistent AF) and then randomized these patients to either wide area circumferential ablation (WACA) with confirmed PVI or WACA plus rotor ablation. Using a 64 pole basket catheter in both the right and left atrium as well as proprietary mapping software, Dr. Narayan and colleagues observed these rotors in 98% of the patients (79% in the left atrium and 21% in the right atrium). Furthermore, rotor ablation terminated or significantly slowed AF in 88% of the patients. Even more striking was that the 2 year success rate was 84% in the WACA plus rotor ablation patients versus just 51% in the WACA alone patients (p=0.004).

Why is this study so important to the field of AF management? First, it highlights the importance of rotors as a new trigger/substrate to the maintenance of AF. Second, ablation of these rotors, in addition to WACA, can dramatically improve the maintenance of sinus rhythm. Third, targeting rotors, in addition to WACA, significantly minimizes the amount of myocardial tissue targeted in ablations. This, in turn, could represent a very efficient and potentially safer approach to AF ablation with minimal impact to atrial function following ablation.

How does this study fit into our current understanding of AF ablation? We suspect that the MAZE procedure, CFAE ablation approach, as well as the step-wise ablation approach, likely inadvertently target/interrupt many of these rotors in both atria. We also suspect that a large percentage of these rotors likely reside around the pulmonary veins and on the posterior wall of the left atrium, which would explain why aggressive “atrial debulking” with posterior wall ablation and ablation at ganglion sites can often terminate AF. Lastly, the rotor ablation could represent a much more “targeted” or focused CFAE ablation approach without the need to “pepper” or “shotgun” both atria with many potentially unnecessary ablation lesions.

For the rotor ablation approach to truly represent a paradigm shift in our treatment of AF, the work by Narayan and colleagues now needs to be reproduced at other centers. Also, a more detailed understanding of the location of these rotors in humans needs to be provided across various disease states. These location maps may merely add validation to current approaches, or possibly note that additional energy delivery in these areas is required. Just as possible, however, is that these location maps may direct focus elsewhere after PVI, and as such, represents a paradigm shift in the non-pharmacological treatment of persistent and long-standing persistent AF.

On behalf of the Innovations in Cardiac Rhythm Management staff, we would like to thank everyone for such strong support, especially those that were able to stop by in the exhibit hall at the HRS annual sessions. Your continued encouragement is greatly appreciated.

John Day, MD, FHRS, FACC
Editor-in-Chief
The Journal of Innovations in Cardiac Rhythm Management
JDay@InnovationsCRM.com
Director of Heart Rhythm Services
Intermountain Medical Center
Salt Lake City, UT

T. Jared Bunch, MD
Atrial Fibrillation Section Editor
The Journal of Innovations in Cardiac Rhythm Management
Jared.Bunch@imail.org
Intermountain Heart Rhythm Specialists
Intermountain Medical Center
Salt Lake City, UT

References

O'Neill MD, Jais P, Takahashi Y, Jonsson A, Sacher F, Hocini M, Sanders P, Rostock T, Rotter M, Pernat A, Clementy J, Haissaguerre M. The stepwise ablation approach for chronic atrial fibrillation--evidence for a cumulative effect. J Interv Card Electrophysiol 2006 Sep; 16(3):153-67. [CrossRef] [PubMed]
Jais P, Hocini M, Sanders P, Hsu LF, Takahashi Y, Rotter M, Rostock T, Sacher F, Clementy J, Haissaguerre M. Long-term evaluation of atrial fibrillation ablation guided by noninducibility. Heart Rhythm 2006 Sep; 3(2):140-5. [CrossRef] [PubMed]
Kalifa J, Tanaka K, Zaitsev AV, Warren M, Vaidyanathan R, Auerbach D, Pandit S, Vikstrom KL, Ploutz-Snyder R, Talkachou A, Atienza F, Guiraudon G, Jalife J, Berenfeld O. Mechanisms of wave fractionation at boundaries of high-frequency excitation in the posterior left atrium of the isolated sheep heart during atrial fibrillation. Circulation 2006 Feb 7; 113(5):626-33. [CrossRef] [PubMed]
Ryu K, Shroff SC, Sahadevan J, Martovitz NL, Khrestian CM, Stambler BS. Mapping of atrial activation during sustained atrial fibrillation in dogs with rapid ventricular pacing induced heart failure: evidence for a role of driver regions. J Cardiovasc Electrophysiol 2005 Dec; 16(12):1348-58. [CrossRef] [PubMed]