Hybrid Procedure May Offer Better Outcomes for Persistent and Longstanding Persistent Atrial Fibrillation
February 9, 2011 — A new strategy, hybrid ablation, for treating persistent and longstanding persistent atrial fibrillation was discussed at the recent Boston AF Symposium. Hybrid ablation is a dual approach in which an electrophysiologist ablates from inside the heart and a cardiac surgeon ablates on the outside of the heart. This combined approach could improve success rates for patients with persistent and longstanding persistent afib who want a minimally invasive (closed chest) treatment option.
Unlike paroxysmal afib, which is caused by triggers that most often are inside the pulmonary veins, persistent atrial fibrillation is a more complex disease. Persistent afib is characterized by changes in the atrial tissue and muscle (substrate modification) that leads to chaotic electrical activity. Thus, patients who have persistent or longstanding persistent AF need more areas in the heart ablated than what is done in pulmonary vein isolation, the cornerstone of catheter ablation techniques.
Hybrid Ablation Combines Best of Both Approaches
In his speech at the Boston AF Symposium, Dr. James Edgerton, a cardiac surgeon at The Heart Hospital Baylor Plano in Texas, said that “hybrid ablation makes sense” because it combines the most effective portions of afib surgery and catheter ablation. According to Dr. Edgerton, “Hybrid ablation is better than either afib surgery or catheter ablation alone in terms of effectiveness, and it also should reduce complications.”
Higher success rates and fewer complications are possible because each specialty (electrophysiology and cardiac surgery) can ablate areas of the heart that are best suited to their different approaches. For instance, electrophysiologists are better able to ablate certain parts of the heart, such as the right atrium, coronary sinus, and cavotricuspid isthmus (where the tricupsid heart valve meets the inferior vena cava vein). On the other hand, surgeons may have a safer approach to ablate the superior vena cava vein, divide the Ligament of Marshall, and exclude (or occlude) the left atrial appendage. (This diagram of the heart shows many of the above-mentioned structures and veins.)
A hybrid ablation may also enhance the prospects that ablation lines fully penetrate all layers of cardiac tissue. This is known as transmurality and is crucial to stopping atrial fibrillation. Essentially, transmural lesion lines create a “block” that prevents afib from entering and recycling within the heart. However, there are challenges to creating transmural lesions during either a catheter ablation or a surgical mini maze procedure.
Most catheter ablations performed in the US today use radiofrequency energy to make lesion lines on cardiac tissue. If too much radiofrequency energy is applied, serious complications can occur, such as damage to the esophagus or cardiac perforation (ripping). If too little radiofrequency energy is applied, the lesion may not be transmural and the atrial fibrillation could resume because there isn’t an effective “block”.
In a mini maze procedure, surgeons make lesion lines on epicardial tissue (the surface of the heart). According to Dr. Edgerton, who performs about 75 mini maze procedures each year, it can be difficult to fully penetrate certain areas of the heart where the tissue is very thick.
In a hybrid approach, the electrophysiologist performs ablation on endocardial tissue (inside the heart) and the surgeon makes epicardial lesions (outside of the heart). This dual approach could increase the likelihood that ablation lines are transmural, fully penetrating the cardiac tissue, and thus blocking aberrant electrical circuits.
A separate presentation at the Boston AF Symposium adds support to a hybrid ablation approach. Dr. Maurits Allessie, of Maastricht University in The Netherlands, presented an interesting hypothesis as to why persistent atrial fibrillation may be harder to treat. In his study, the 24 patients with persistent afib had four times the number of “focal fibrillation waves” (afib activity), and a greater incidence of them in the right atrium, when compared to the 25 paroxysmal patients.
None of the patients with persistent afib had obvious trigger points for atrial fibrillation. In addition, neither Dr. Allessie nor his researchers could find re-entry points for afib in these persistent patients. From this, Dr. Allessie has formed what he calls the “Double Layer Hypothesis”, where narrow wavelets in the inside and outside (endocardial and epicardial) layers of heart tissue “constantly feed each other” in persistent afib. If Dr. Allessie’s Double Layer Hypothesis is confirmed by larger studies, it could add further support as to why hybrid ablation might be better able to treat persistent atrial fibrillation.
Dr. Edgerton presented data on 12 persistent AF patients who received hybrid ablation at the University of Virginia and University of Maastricht. At 12.5 months of follow up, 83% of patients were free from atrial fibrillation and off antiarrhythmic drugs. Although this was only a small group of patients, the results are promising. Comparatively, catheter ablation by itself has had far lower success rates in treating patients with persistent atrial fibrillation—success rates of 20%-50% for a single procedure and 60% for multiple procedures—according to a symposium at the Heart Rhythm Society 2010 meeting.
Laying the Groundwork for Hybrid Ablations
Only a few centers in the US currently perform hybrid ablations. That may be because cardiac surgeons and electrophysiologists are said to have a somewhat adversarial relationship stemming from a turf battle over patients. Although that’s not the case at every center, there’s enough truth in the statement that doctors joke about it. In fact, Dr. Edgerton did joke that he was the “token” cardiac surgeon at the Boston AF Symposium.
That is beginning to change, however, with some leading surgeons and electrophysiologists routinely collaborating on the optimal treatment for a patient. (At Dr. Edgerton’s center, collaboration is the norm, and electrophysiologists and surgeons work as a true team.) In addition, several centers are preparing to participate in the Dual Epicardial Endocardial Persistent AF (DEEP AF) clinical study that will enroll 30 patients with symptomatic persistent or longstanding persistent AF for hybrid ablation treatment. If DEEP AF shows positive results, a larger study could be planned.
Separately, results were presented at the Boston AF Symposium for another procedure involving collaboration of surgeons and electrophysiologists. This one is called the Convergent Procedure. At seven months, 72% of the 43 patients with longstanding persistent atrial fibrillation were in normal sinus rhythm and off antiarrhythmic medication, but a US clinical trial for this Convergent Procedure has been stopped following two deaths (one related to stroke, the other stemming from damage to the esophagus). While the hybrid and convergent procedures are similar, the methods used for surgical access to the heart are different as are the lesion lines for both the surgical and catheter ablation portions of these procedures.
The hybrid procedure holds great promise, and Dr. Edgerton, who has been a pioneer in advancing the treatment of atrial fibrillation, said that scientifically conducted trials are needed. Referring to the DEEP AF clinical trial in which his center is participating, Dr. Edgerton commented, “We continually strive to improve the treatment of our patients. I look forward to being able to report improved outcomes with the hybrid approach in the near future. Stay tuned.”
See related information:
- Dr. James Edgerton Discussing Treatment Options — Video
- Catheter Ablation
- Mini Maze (Surgical Ablation)
- DEEP AF Clinical Study
- Ligament of Marshall: Why It Is Important for Atrial Fibrillation Ablation
Disclaimer: Patients come first at StopAfib.org, and we do not compromise on that. While Dr. Edgerton serves on the StopAfib.org medical advisory board, and AtriCure, which is sponsoring the DEEP AF clinical trial, is a donor to StopAfib.org, we believe that key presentations at medical meetings must be reported to give patients an all-encompassing view of current and future treatment options. Therefore, we feel that it is important to report on Dr. Edgerton’s presentation at the Boston AF Symposium.