Dr John Mandrola practices cardiac electrophysiology in Louisville, KY. He finished training at Indiana University in 1996. His practice encompasses catheter ablation, including an eight-year experience with AF ablation, device implantation, and consultative EP. Outside of the EP lab, Dr Mandrola's two hobbies include competitive cycling and writing. He has maintained a medical, fitness, and cycling blog, Dr John M, for the past two years.
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Can catheter ablation of AF ever be compatible with a less-is-more approach?Mar 18, 2013 10:56 EDT
Here's a challenge: Pick up a cardiology or electrophysiology journal and show me a negative piece about catheter ablation of atrial fibrillation. It's true; our world is mostly free of doubters.
Then there is the real world, one populated with other medical specialties, and those daring enough to ask, "What, exactly, are you ablating?" As it turns out, not all doctors think so highly of the notion of ablating a disease that we do not fully understand.
Dr Rita Redberg, influential cardiologist and editor of the JAMA Internal Medicine "Less is More" series, said this about ablating AF:
"Because ablation has never been studied in a randomized blinded fashion, we cannot know whether patients experience fewer symptoms after ablation because subjective symptoms frequently decrease following a procedure or whether the ablation itself was beneficial.
Furthermore, the clinical benefit on survival and morbidity of this invasive procedure, which has substantial procedural risks, remains to be established."
As one who makes a living burning and freezing in the left atrium, these are stirring words. An attached electrophysiologist might even get mad. That sort of reaction, however, could lead to inflammation, a potential cause of AF. Perhaps a more useful approach would be to consider such critique as a challenge—a call to explain what we are up to behind those leaded walls. I have about 800 words.
Let's start by setting out two points of agreement (always lead with the positive). First, I am a strong believer in the less-is-more philosophy. Cardiologists have too often strayed from this guiding principle. Second, it is also true that few large randomized controlled trials of AF ablation have been done. The CABANA trial is enrolling now, but the answers are many years away, and surely, the ablation procedure tested will be obsolete by then.
In the meantime, more than a million humans seek advice for their fibrillating atria. Grinning and bearing the disease surely adheres to a less-is-more philosophy, but that treatment is neither fair nor compassionate. Antiarrhythmic drugs are also a deeply flawed therapy. And what of that time penalty: the longer one stays in AF, the harder it is to treat.
And this is the point. Patients with AF that persists despite lifestyle maneuvers face tough choices: They can live with their disease, take drugs, or have an ablation. ( I can attest that having AF changes your view of treatment options. Perchance the critics of AF ablation haven't had to call their wife to come pick them up from a bike ride because they were too weak to go on?)
Enter pragmatism. We know rhythm-control drugs for AF are terrible. They lack efficacy, cause side effects, and most important, confer real risk. The default thinking—that taking a pill is less risky than a procedure—does not apply to rhythm-control drugs for AF. Prolongation of the QT interval, 1:1 atrial flutter, and postconversion pauses present clear and present dangers.
An image might help: picture the sun-worn 65-year-old triathlete pedaling himself through the pain threshold up a big climb. Now picture him doing the same on propafenone or flecainide. That's risk.
Do not misunderstand; AF ablation isn't free of risk. Tamponade, stroke, esophageal damage, vascular complications, and phrenic nerve injury, among others, are serious issues. That said, however, in 2013, at least in my laboratory, the risk of major complications is less than 1%. (Yes, we have [our] data.) Most EP centers have similar numbers, especially if one looks at results from the past two to three years. The procedure is safer now. Don't take my word, though; in the MANTRA-PAF trial (NEJM), major adverse events did not differ between ablation and drug arms.
AF ablation in 2013 has come a long way. Due to technological advances (low-flow irrigated ablation catheters and 3D mapping systems), learning curves (the human component), and establishment of standardized approaches (durable pulmonary vein isolation in all), AF ablation has been transformed. The 2013 procedure is low in radiation exposure, well-practiced, and mainstream. Gone is mystique and magic. Ablation cowboys have been domesticated. Most of us drive minivans.
Now let's talk about outcomes
As a given, let's agree that quality of life and exercise capacity are important patient outcomes. In this category, AF ablation is superior to drugs. Although there will be quarrels about the word "success" and "cure," it is clear that most patients who are able to endure multiple ablation procedures end up feeling better than those who stay on drugs. Feeling better is an important end point, isn't it?
On the matter of hard end points (or long-term outcomes), like stroke and mortality, the picture is cloudy. The AFFIRM trial taught us that employing a rhythm-control strategy with AF drugs does not lower stroke or death rates. Being in sinus rhythm is good, but not so much if you get there with AF drugs. Will it be the same story for ablation? Optimists argue that since the procedure is more successful than drugs, it stands to reason long-term outcomes will follow. We shall see, but it's going to take years to know. While we wait for randomized controlled trials there are preliminary data worthy of a look.
During this session of the American College of Cardiology 2013 Scientific Sessions, two abstracts compared populations of AF patients who had or did not have ablation. Although these sorts of studies are nonrandomized and retrospective and therefore limited in power and scope, they are all that we have until CABANA is available.
In the larger of the two abstracts, University of Utah investigators studied a database of 13 751 AF patients, 1099 of whom had catheter ablation between 2006 and 2012. The incidence of stroke was 4% in the ablation group and 12.8% in the nonablation group. This led to a highly significant hazard ratio of 0.29. The problem with saying too much about these data was that the catheter-ablation cohort was younger and more likely to be on warfarin. Was the lower stroke incidence due to the ablation or just that the ablation cohort was at lower risk?
In the second poster right next door, South Korean investigators performed a similar look-back population analysis. They took 586 patients with AF who had AF ablation (2003–2009) and compared them with matched controls. Again, patients who underwent ablation enjoyed a 61% lower risk of stroke.
These are not the only trials that have looked at the long-term results of AF ablation. This one from Beth Israel investigators found similar reductions in stroke in those who had prior AF ablation. And this trial from the Intermountain group in Utah showed that AF ablation might confer a lower risk of developing dementia.
Taken together, association trials at least hint at the possibility of long-term benefit from AF ablation. Association never means causation, but my conflicted eye has trouble seeing any signal for harm.
My one-paragraph summary response to Dr Redberg
I hear you about AF ablation. It is a big hammer. It bothers me doing all those burns and freezes. But the disease sucks. And so do the supposedly safer medical options. So far, I see four themes of AF ablation:
1. There is a (strong) hypothesis that AF ablation improves long-term outcomes.
2. When done skillfully, there is little signal of long-term harm.
3. There is a high likelihood of symptom relief.
4. There is a dearth of other good alternatives.
So yes, I think AF ablation is an especially reasonable and compassionate therapy to discuss with patients.