Maximizing Ablation, Limiting Invasiveness, and Being Realistic About Atrial Fibrillation: The Convergent Hybrid Ablation Procedure for Advanced AF

M. Clive Robinson, MD, FRACS, Murali Chiravuri, MD, PhD, Craig McPherson, MD, Robert Winslow, MD CT Cardiac Arrhythmia Center at Bridgeport Hospital Bridgeport, Connecticut
M. Clive Robinson, MD, FRACS, Murali Chiravuri, MD, PhD, Craig McPherson, MD, Robert Winslow, MD CT Cardiac Arrhythmia Center at Bridgeport Hospital Bridgeport, Connecticut

Overview

In the past, atrial fibrillation (AF) was viewed with relative indifference. It is now recognized for its increasing prevalence, its anatomical, electrical, and pathological complexity, and for the challenges it has brought to the interventional therapy realm. As the clinical effects of AF have become more visible, and with disenchantment with antiarrhythmic drugs, the guidelines for treatment have changed to now more frequently incorporate interventional procedures. However, as experience has broadened, particularly with catheter-based methods, and most noticeably in persistent and longstanding persistent AF, outcome analysis has often shown less than impressive results.1,2 Although certain surgical options have shown promise, the magnitude of these procedures has limited their wide adoption.3  

The field of AF treatment has been confounded by almost every aspect of this arrhythmia – the complex and elusive nature of AF, variability in ablation techniques and energy sources and, in particular, deficiencies in quantifying AF burden pre and post treatment. It would seem there is a paradoxical duo in our current expectation of interventional outcomes. Most cardiovascular therapies are palliative, yet with the particularly complex problem of AF, we have set disproportionately high expectations of success. A therapeutic goal of less than 30 seconds of recurrent arrhythmia contrasts with the insensitive levels of scrutiny based on EKG and 24-hour continuous monitoring alone. Therefore, results in the literature are often more reflective of levels of diligence in clinical scrutiny and rhythm monitoring than on procedural efficacy. Objectives would, perhaps, be more meaningful if they measured reduction in AF burden and clinical success rather than electrical success as a benchmark for therapy efficacy. 

In the context of these considerations, it would seem that to justify procedures for AF alone, the procedures need to be characterized by limited invasiveness and low risk, be well tolerated with short hospital stay, and more comprehensively disable the multiple mechanisms of AF. 

We present a review of our experience with the convergent hybrid procedure and, in particular, the principle of our technique of extended posterior left atrial wall ablation, and its role in treating cases of advanced AF with severely enlarged left atrias. 

The Convergent Hybrid Procedure

The convergent procedure is performed by both the EP cardiologist (for endocardial ablation) and cardiothoracic surgeon (for epicardial ablation). It is minimally invasive, and is most efficiently conducted as a single procedure in the cath lab. The technique is designed to mutually facilitate pulmonary vein isolation and to enhance and expand posterior left atrial wall ablation. This makes the method particularly suitable for persistent and longstanding persistent AF of any left atrial size. 

The epicardial ablation is performed first and involves an entirely soft tissue endoscopic approach to the pericardium with port access through a one-inch upper abdominal incision and two instrument ports, crossing the central tendon of the diaphragm to enter the pericardial space (Figure 1). The method avoids sternotomy, cardiopulmonary bypass, thoracotomy, lung collapse and pericardial dissection. The left atrium is directly visualized, including the confluence of right and left pulmonary veins and the pericardial reflections. A 3 cm x 6 mm radiofrequency suction ablation device (Numeris® Coagulation System, nContact, Inc.) is applied, which allows delivery of unipolar energy lines directed away from the esophagus onto the posterior wall of the left atrium, and adjacent to the pulmonary veins, both posteriorly and anteriorly. As part of our experience, we have developed and routinely perform extended posterior wall continuous epicardial ablation. Once completed, the endocardial component is carried out with mapping and completion of pulmonary vein isolation, placement of additional ablation lesions, if required, and routine delivery of a right cavotricuspid line. 

Development of Extended Posterior Left Atrial Wall Ablation

At Bridgeport Hospital, we have developed the technique of extended left atrial posterior wall ablation. Rather than the usual ablation lines that are placed along the roof or variably on the perimeter of the posterior left atrium, our method is expanded so as to confluently and directly ablate and debulk the AF mechanisms of the atrial substrate. Using the Numeris® Coagulation System, multiple adjoining parallel ablation lines are placed spanning the transverse and vertical height of the atrium posteriorly. The number of ablations depends on atrial dimensions and almost invariably includes two vertical rows. Figures 2 and 3 schematically show a typical pattern of ablations. Routine postablation endocardial mapping typically shows a silent posterior left atrial wall. 

The rationale for extended posterior wall ablation is based on several considerations: 1) The traditionally used single linear or spot ablation lesions are notoriously prone to gaps, partial thickness and reconnection. 2) The posterior left atrium (embryologically derived from pulmonary venous musculature) is the most anatomically concentrated location of arrhythmogenic mechanisms (rotors, triggers, autonomic ganglia), particularly in persistent and longstanding persistent AF. 3) The cumulative effect of multiple adjoining ablation bands, by direct impact may more effectively disable the numerous and often dynamic foci of AF, correcting for the deficiencies of unipolar and bipolar box lesion sets. 4) The technique more closely mimics the Cox III posterior wall method. 5) Finally, the extended ablation of the posterior wall enables reduction in the need for endocardial lesions with the benefit of reduced radiation and time, less potential for esophageal injury, and less endocardial char. 

All interventions for AF have issues and deficiencies, and none can be regarded as a cure. Recognized limitations of the convergent procedure and other treatment options include management of the mitral isthmus and proarrhythmic risk, and dealing with the left atrial appendage (left undisturbed in this procedure). 

It is understood that the approach we describe is also at variance with techniques based on sophisticated mapping designed for more focal, target-specific ablations.

Post Procedure Follow-Up

The follow-up protocol in our study included prescribing antiarrhythmic drugs and anticoagulantsduring the first three months post procedure (blanking period), with office visits every 2-4 weeks. Following the blanking period, visits were 4 to 12 weeks apart, and two 14-day periods of continuous monitoring were performed over the subsequent 12 months and after antiarrhythmic drug washout. 

Clinical Outcomes

Between June 2011 and April 2013, 42 patients — 57% (24/42) persistent AF patients and 43% (18/42) longstanding persistent AF patients — received the convergent procedure at our hospital. Patient baseline characteristics included persistent or longstanding persistent AF, failed antiarrhythmic drug therapy, failed prior endocardial ablations, and those otherwise considered unsuitable for stand-alone endocardial catheter ablation. Six patients had a BSA greater than 40. The average length of hospital stay was 2.9 days. Average follow-up was 13 months. Table 1 details the demographics of the 42 patients.

Of the 42 patients who received the convergent procedure, 6 patients are still within the blanking period. Of the 36 patients who are past the blanking period, 89% (32/36) are in sinus rhythm (SR), and 69% (25/36) are in SR and off antiarrhythmic drug therapy, with an average follow-up of 13 months. 

Of the 7 patients in SR and on antiarrhythmic drug therapy, 2 patients have undergone an ablation for atrial flutter (1 left sided and 1 right-sided). Four patients have significant residual atrial fibrillation-flutter.

There were no procedural or post procedural mortality or esophageal fistulas reported. The less than 30 days major complication rate was 7% (2 tamponades, 1 TIA/stroke). Three patients experienced pericarditis that resolved with treatment and four patients had incisional hernias.

Discussion

The convergent procedure is an emerging experience in the interventional AF field. To date, we have been impressed by the results. This is a subset of patients with advanced atrial fibrillation, including markedly enlarged left atria, whose outcomes have been subject to stringent levels of scrutiny. The convergent procedure is based on the logic of limited invasiveness and a comprehensive ablation strategy, and may represent the optimal balance between these two factors. Perhaps the most notable feature of the technique is the extended posterior wall ablation, which directly impacts and disables the multiple mechanisms of atrial fibrillation in the posterior left atrium. The results, to date, appear to have validated this procedure in atrial fibrillation patients otherwise excluded from intervention or for whom poor outcomes have been likely. 

Atrial Fibrillation in Healthcare Accountability

In current healthcare policy and purchasing, cost benefit aspects of procedures and services are under increasing scrutiny. With AF in particular, the prevalence, cost, variable procedures, and less than impressive outcomes to date, will make this condition a likely focus for such accountability and critical analysis. If physicians fail to respond to these discerning metrics, the future of these procedures will become questioned only too quickly and perhaps misguidedly by hospital administrators, CMS, and healthcare insurers. The convergent procedure will receive equal attention in this process of determining its role and contributions in enhancing the range and efficacy of interventions for this difficult condition.

Conclusion

Philosophically, the convergent procedure requires cooperative initiatives between the surgical team and the EP lab team. If this cooperation is achieved the results will prove to be greater than separate EP and surgical initiatives. We are pleased to be a national training site for this approach.

Disclosures: M. Clive Robinson, MD, FRACS is a training consultant and proctor for nContact; Murali Chiravuri, MD, PhD is a training consultant for nContact; Robert Winslow, MD receives consulting honoraria for Janssen Pharmaceuticals and research support for Boston Scientific and BIOTRONIK.

References

  1. Weerasooriya R, Khairy P, Litalien J,, et al. Catheter ablation for atrial fibrillation: are results maintained at 5 years of follow-up? J Am Coll Cardiol. 2011;57:160-166.
  2. Sorgente A, Tung P, Wylie J, Josephson ME. Six year follow-up after catheter ablation of atrial fibrillation: a palliation more than a true cure. Am J Cardiol. 2012;109:1179-1186.
  3. Boersma LV, 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(1):23-30.

This article was part 2 of a series that started last month; check out the first article on pages 58-59 in the May 2013 issue.