Can Catheter Ablation Successfully Treat Persistent Atrial Fibrillation
June 14, 2010 6:05 AM CT
By Christine Welniak
Atrial fibrillation is a progressive disease that can become more severe over time as AF “remodels” the heart. This results in multiple areas in the atrium that could become “triggers” for AF, areas where afib is initiated or can “re-enter” to cycle throughout the heart.
The pulmonary veins (PVs), which transport blood to the atria, are the trigger points for 97% of people who have paroxysmal afib, according to Dr. Christopher Cole, of Colorado Springs Cardiologists, who presented at Heart Rhythm Society 2010. On the other hand, 20% of the triggers for patients with longstanding persistent AF, that which has lasted more than a year, are in other parts of the atrium. Thus, pulmonary vein isolation—the catheter ablation technique most often used for paroxysmal patients—by itself isn’t likely to eliminate afib for patients who have persistent or longstanding persistent AF.
To make matters more challenging, the “extra” triggers that patients with persistent afib have are often dispersed through different parts of the atrium and are different for every patient with AF. Electrophysiologists who do catheter ablations agree that more extensive ablation lesion sets (where the ablation lines are located) are needed to treat persistent and longstanding persistent afib, but they are still trying to identify the optimal ablation strategy for these patients.
Pulmonary vein isolation is the starting point for most of these strategies. But pulmonary vein isolation can mean different things to different doctors, Dr. Cole cautions. Indeed, it has become a catch-all term for catheter ablation of the pulmonary veins.
Dr. Cole personally uses a pulmonary vein antral isolation (PVAI) strategy. It entails a wide lesion set, which means ablating in the atrium just beyond the base of the pulmonary veins. For his paroxysmal patients, Dr. Cole also ablates along the superior vena cava. You can see where the pulmonary veins and superior vena cava are located on this diagram of the heart.
For his persistent and longstanding persistent afib patients, Dr. Cole uses a more sophisticated ablation strategy. In addition to ablating the pulmonary veins and the superior vena cava, he creates ablation lines along one wall of the left atrium as well as a line along the septum, the wall that separates the right and left sides of the heart.
Dr. Cole presented results on 1,362 patients—730 paroxysmal, 295 persistent, and 337 longstanding persistent AF patients. Despite the more extensive lesion sets, persistent and longstanding persistent afib patients still had lower success rates than patients with paroxysmal AF. When a single ablation was performed, paroxysmal patients had 10% higher success rates, and 8% higher with more than one ablation. “Success rates really drop off in the longstanding persistent group,” says Dr Cole.
Analysis showed that the duration of AF was a factor in ablation outcome. That is, patients who had had atrial fibrillation for a longer period of time didn’t respond as well to ablation as those who had had it for a shorter period. In addition, an enlarged left atrium or the presence of structural heart disease, such as valve disease, resulted in lower success rates. See Predictors of Ablation Success for what was presented on this topic at Heart Rhythm Society 2010.
Dr. Cole also discussed a recent review in Heart Rhythm Journal by Anthony Brooks, PhD, and colleagues. This research was notable in that it aggregated data from 32 clinical studies and looked at outcomes of various catheter ablation techniques—including different pulmonary vein strategies—for treating persistent and longstanding persistent afib.
In evaluating quality randomized clinical trials, the researchers found that Dr. Cole’s technique, pulmonary vein antral isolation, “is a superior approach to PVA [pulmonary vein antral] ablation alone.” Pulmonary vein antral ablation is a procedure that also creates a wide lesion set around the base of the pulmonary veins but doesn’t confirm that the pulmonary veins have been isolated, or blocked. Not all electrophysiologists confirm block, which is why it’s important to ask your doctor if he or she verifies that the pulmonary veins have been completely isolated.
Researchers also looked at outcomes for patients who had a more sophisticated technique, ablation of complex fractionated arterial electrograms (CFAE, pronounced cafe). CFAE may be performed on persistent and longstanding persistent afib patients as they often have triggers elsewhere in the atrium besides the pulmonary veins. When using a CFAE ablation strategy, doctors try to induce atrial fibrillation to locate those areas that allow AF to re-enter, known as “macro re-entry sites”.
CFAE results have not been conclusive, however. In the Brooks’ review, CFAE ablation did not increase the success rates for patients with longstanding persistent AF, and the study concluded that CFAE “is an inferior strategy compared to PVA [pulmonary vein antral] ablation plus linear ablation at the roof and mitral isthmus.”
Brooks’ research showed catheter ablation success rates of 20%–50% with one procedure for patients with persistent or longstanding persistent afib, and 60% when the patient underwent more than one procedure. When multiple procedures were performed and antiarrhythmic medication was used as well, the success rate reached 70%–80%. Overall, with so many different techniques used along with differing monitoring, follow up, and patient selection, the results were inconclusive.
What does that suggest for catheter ablation treatment of the more severe forms of afib? “The jury is still out on the best lesion set,” Dr. Cole conceded.
Electrophysiologists at the session were given the opportunity to vote on the ablation strategy they use to treat persistent atrial fibrillation. The majority reported using a “step-wise” approach where the doctor generally starts with pulmonary vein ablation or isolation followed by additional lesion lines. Those lesion lines could include ablation along the roof of the left atrium, the coronary sinus, the mitral isthmus, the septum, and other areas of the heart.
Once the pulmonary veins have been ablated, the sequence used depends on the individual doctor, as there isn’t one specific sequence that has proven to be best. A couple of reasons for that include:
- Few electrophysiologists conduct clinical trials on specific ablation strategies or lesion sets and instead rely on what has worked with their patients.
- Results from trials often aren’t comparable due to differences in follow-up and monitoring.
As indicated by Dr. Cole, while much progress has been made, there isn’t a single catheter ablation approach or strategy that has been proven to be the best for treating persistent or longstanding persistent afib because it is so difficult to ablate. In fact, there was a debate at Heart Rhythm Society as to whether surgery is actually better than catheter ablation for these most difficult cases.
The debate will continue, but at this point the only proven high success rates for persistent and longstanding persistent afib are from the Maze procedure, which is an open-heart procedure and thus the most invasive.
One very encouraging direction is the newer hybrid or convergent procedure, which combines minimally-invasive surgery, called the mini maze procedure, with catheter ablation. By offering the best of both worlds, these procedures have the potential to radically alter the prognosis for those with persistent and longstanding persistent atrial fibrillation. For more on the status and direction of hybrid procedures, see our video interview with Dr. Andrea Natale.
Read related information:
- Outcomes of Persistent and Longstanding Persistent AF Ablation, Heart Rhythm, June 2010
Christine Welniak writes about atrial fibrillation and other heart diseases/conditions for patients, medical professionals, and investors.
Mellanie True Hills is founder and CEO of StopAfib.org and an atrial fibrillation survivor.