How Do You Define Success?
Peter A Noseworthy, MD: I am Dr Peter Noseworthy, assistant professor of medicine and electrophysiologist at Mayo Clinic. During today's Mayo Clinic talks, we will be discussing, "When Ablation Fails—What Next?" I am joined by Dr. Paul Friedman, professor of medicine at Mayo Clinic, who specializes in electrophysiology. So before we talk about why ablation fails and what that means, let's take a step back and first talk about success. How do we define success with ablation?
Paul A Friedman, MD: In someone who has had weekly or daily episodes of atrial fibrillation [AF], a recurrence at 1 or 2 years that is very infrequent and easily controlled could be considered a success. The primary indication for ablation of AF is control of symptoms. A secondary indication is left ventricular dysfunction. In that setting success is, in large measure, defined by whether you have improved the patient's quality of life, whether the AF is no longer the main focus of the patient's daily activities and the patient has moved on with well-controlled symptoms. Many of the clinical-trial end points have included symptom scores, but they have also included documented AF; and some have used durations as short as 30 seconds. There has been a lot of heterogeneity among clinical trials in terms of recurrence of AF and whether it is symptomatic, and that has to be kept in mind when you start quoting the outcomes of clinical trials.
Dr Noseworthy: I find that patients often want a number. What are you telling patients now?
Dr Friedman: In part, it depends on who the patient is and the patient's background. If you lump together all patients with AF ablation, what is the success rate? It's useful to think about it in the intermediate term, not the short term. Many trials are 1 year, but people want to know—what about 3 years or 5 years—especially because most of the people studied were in their late 50s or early 60s, and some were in their 70s. A recent meta-analysis looked at that question—what is the outcome at 5 years following ablation? If you permit repeat ablation in people who clearly have failed, the success rate is just under 80% for paroxysmal AF. For patients with persistent nonparoxysmal AF, it drops down to about 60%.
The other issue is how often do patients require more than one procedure? If you go out to 5 years, the average number of procedures per person is 1.5, meaning that roughly half will need a second procedure. What is the single-procedure success rate? That drops down quite a bit, as you might imagine. It's between 50% and 55% at 5 years. The 1-year shorter term success rate is significantly higher. A key factor in determining the success rate depends on how persistent and how longstanding the arrhythmia is.
The Ideal Ablation Patient
Dr Noseworthy: It sounds as though the pattern of AF is the key. Are there other patient factors that go into that success rate?
Dr Friedman: Yes. The amount of structural heart disease has a bearing on its own. Marked left atrial enlargement reduces the likelihood of maintaining normal sinus rhythm. The recurrence rate is, in part, affected by such comorbid conditions as hypertension, diabetes, and obstructive sleep apnea. Those are important because there are a lot of things that nonelectrophysiologist physicians can do to maintain the wellness of their patients and perhaps lower the risk for arrhythmia recurrence.
Dr Noseworthy: Referring physicians often ask me to describe the ideal patient for ablation. Can you describe for me the ideal patient for an ablation and also "the extreme" for an acceptable patient?
Dr Friedman: The ideal patient is someone who has normal body habitus, normal body mass index, the paroxysmal pattern of arrhythmia (that is, it starts and stops without the need for medical intervention), has normal left atrial size, normal ventricular function, and has not had the arrhythmia for a prolonged period of time. Some evidence suggests that when the time from the date of onset of the arrhythmia to when you ablate is delayed, the likelihood of success may drop a little bit. These are retrospective data, but they are intriguing. That would be the ideal candidate. In that person, you may start to approach (although we don't have trial data to support it) success rates of up to 90%, at least for 1 year.
The Less-Than-Ideal Patient
Dr Friedman: The other extreme would be a patient with longstanding persistent AF (a continuous arrhythmia present longer than a year) in whom, to restore sinus rhythm, a cardioversion is required, and the pattern would typically revert back to AF quickly. This is typically an older person with multiple comorbid conditions (eg, obesity, diabetes, hypertension). If you really want to make it a difficult candidate, you can include other structural anomalies, such as valvular heart disease—conditions that lead to atrial stretch, atrial fibrosis, and more pathology, making it harder to maintain homeostasis—and by that, I mean a normal rhythm.
Dr Noseworthy: Would you still be willing to perform ablation in patients with compelling indications?
Dr Friedman: The more comorbid conditions, the more compelling the indication needs to be; and the most compelling indication is highly symptomatic atrial fibrillation. There have been roughly five or six trials[3–8] and a couple of meta-analyses[9,10] comparing drugs with [first-line] ablation in patients who are symptomatic, and ablation has been consistently superior to drugs for controlling symptoms. In patients who are asymptomatic, it's far more difficult. We do not have evidence at this time that restoring sinus rhythm with ablation frees someone from stroke risk.
We would like to think it does, but we don't know that yet, so the rationale for anticoagulation is based on the risk for thromboembolism before the ablation procedure. That is not a strong indication. In a high-risk patient who has no symptoms, especially an older patient, I would be less inclined to do the procedure. The current guidelines for a patient who is symptomatic, especially someone who is paroxysmal and younger, suggest performing ablation before using antiarrhythmic drugs. Patient preference enters into this, and shared decision making is important in these areas where the evidence base is mounting and we don't have any confirmed mortality benefit at this time.
Capitalizing on Patient Motivation
Dr Noseworthy: For a patient to go through with an ablation, that marks that patient as being motivated in terms of trying to improve his or her health. These patients often ask what they can do in terms of lifestyle modification. Do you have any comments on that?
Dr Friedman: That's right, and it's important. We have control over several factors that can affect the risk for AF fibrillation. There has been a strong association between obesity and AF. Weight loss is extremely difficult, but increased physical activity and appropriate dietary modifications to reduce weight can help. The second thing is ingestion of stimulants such as caffeine and alcohol. Alcohol, in particular, has been shown to be associated with AF, especially at higher doses. We don't usually think of alcohol in terms of "doses," but the "holiday-heart syndrome" has been described in people who binge drink, and chronic alcohol ingestion is also associated with arrhythmias. Drinking in moderation, which would be one glass of wine [a day] for a woman, or one to two for a man, has not been shown to be strongly associated with AF and is reasonable. The goal is not to curtail people's lives in a way that is unpleasant. We still need to enjoy life but to do things in moderation, including alcohol ingestion, food, and physical activity.
Dr Noseworthy: The time of an ablation is an opportunity for us to make interventions on patients' lifestyles, and I wonder whether we sometimes miss that chance. I have heard other electrophysiologists talk about the possibility of referring patients to cardiac rehabilitation after ablation; that is not currently the practice, but I wonder whether in the future, we may see more of that. What are your thoughts?
Dr Friedman: It's an attractive option. It is an opportunity because these are motivated individuals, by and large. Often, they are in their late 50s or early 60s and are at a stage where their weight has been increasing over the years and it's time to take stock. Having physical rehabilitation can both help with the acute procedural recovery and lead to a pattern of behavior and lifestyle that, perhaps, will improve long-term health outcomes, which is what it is all about—feeling better and trying to prevent dementia. There are some retrospective data with AF and preventing other cardiovascular disease, cardiomyopathy, and so on.
The Price of Failure and Diminishing Returns
Dr Noseworthy: Assuming that the patient has done everything he or she can do and we have done everything that we can do and we have selected the best patients, there will still be patients whose ablation will fail and who will continue to have highly symptomatic AF. What are the options for those patients?
Dr Friedman: Failure means failing, and failing at an experienced center because there are various techniques for the procedure. Assuming that the ablation was done at a center that does many hundreds of procedures annually and has full access to all the techniques, there are patients in whom it will fail. In that setting, it comes down to three options—pharmacologic treatment, which has often failed by the time patients get to that stage; other nonpharmacologic options—one of which is surgical therapies. The literature on the surgical maze procedure following failed catheter ablation is relatively limited, and we don't have a deep, robust sense of how effective that surgery is. Often, we switch to nonpharmacologic rate-control strategies, such as atrioventricular node ablation with device implantation. This is extremely effective for controlling symptoms, and although often less attractive for younger individual, it is acceptable for patients in their mid-70s and older because it essentially eliminates the need for pharmacologic therapy, with the exception of anticoagulation for stroke prevention. That starts to become a more attractive option after left atrial and right atrial ablation have been attempted.
Dr Noseworthy: How many ablations are reasonable? Are there diminishing returns in the patient who is not responding to ablation?
Dr Friedman: That's a great question and one that is incompletely studied. It is very reasonable to do two ablations; half of all people will have two. In the ideal candidate, a younger person who is highly symptomatic and a highly motivated person, a third ablation is not unreasonable. It should be an infinitesimal number of people in whom you go beyond three ablations. Here I am referring to left atrial ablation to restore normal rhythm. At some point, you have to say, this isn't going to be the approach for this individual.
Dr Noseworthy: That's a hard position to be in, but certainly one that we find ourselves in from time to time. Thank you for these very important insights and to our listeners for tuning into Mayo Clinic Talks on theheart.org on Medscape Cardiology.