Cardiorespiratory Fitness May Alter AF Ablation Outcomes

Fran Lowry

August 04, 2020

Higher baseline cardiorespiratory fitness (CRF) is associated with better outcomes after atrial fibrillation ablation, according to new research.

In a single-center retrospective cohort study, patients with the highest level of baseline CRF had significantly lower rates of arrhythmia recurrence and death than patients with lower levels of CRF.

Wael Jaber

"It is stunning how just a simple measure, in this case walking on a treadmill, can predict whether atrial fibrillation ablation will be a successful endeavor or if it will fail," senior author Wael A. Jaber, MD, professor of medicine, Cleveland Clinic, told | Medscape Cardiology.

"We found that ablation was not successful in most patients who had poor functional class and, conversely, that it was successful in most patients who were in tip-top shape when they walked on the treadmill. Our results can help clinicians inform patients about what they can expect after the procedure, depending on the baseline fitness level," Jaber said.

The study was published online August 2 in Heart Rhythm.

Several studies have shown a reduction in AF incidence among individuals who report a physically active lifestyle, but the extent to which baseline CRF influences arrhythmia rates after AF ablation is unknown, the authors note.

For the study, Jaber and colleagues analyzed results in 591 consecutive patients (mean age, 66.5 years; 75% male) with symptomatic paroxysmal or persistent AF who underwent de novo AF ablation at their institution. Only patients who had undergone an exercise stress test in the 12 months before AF ablation (average, 4.5 months) were included.

Age- and sex-specific predicted metabolic equivalents (METs) were calculated using the St. James model for women and the Veterans Affairs referral model for men. The number of METs achieved was then divided by the predicted METs, and the patients were categorized into low (<85% predicted; n = 152), adequate (85% - 100% predicted; n = 115), and high (>100% predicted; n = 324) CRF groups.

Functional capacity was characterized as poor in 56 patients (9.5%), fair in 94 (16.0%), average in 225 (38.1%), good in 169 (28.6%), and high in 47 (8.0%).

During a mean follow-up of 32 months, arrhythmia recurrence was observed in 79% of patients in the low CRF group, 54% of patients in the adequate CRF group, and 27.5% of patients in the high CRF group (P < .0001).

Rates of repeat arrhythmia-related hospitalization, repeat rhythm-control procedures, and the need for ongoing antiarrhythmic therapy (ATT) were significantly lower in the high CRF group.

Specifically, ATT was stopped in 56% of patients in the high-CRF group, compared with 24% in the adequate-CRF group and 11% in the low-CRF group (P < .0001).

Rehospitalization for arrhythmia was required in 18.5%, 38.0%, and 60.5% of cases, respectively, and repeat direct-current cardioversion or ablation was performed in 26.0%, 49.0%, and 65.0%, respectively (< .0001 for both).

Death occurred in 11% of the low-CRF group, compared with 4% in the adequate-CRF group and 2.5% in the high-CRF group. Most (70%) of the deaths were due to cardiovascular events, including heart failure, cardiac arrest, and coronary artery disease. The most common cause of noncardiac death was respiratory failure (13%), followed by sepsis (10%), malignancy (3%), and complications of Parkinson's disease (3%).

"Although there was a statistically significant association between higher CRF and lower mortality in this cohort, the findings are to be viewed through the prism of a small sample size and relatively low death rate," the authors write.

Don't "Overpromise" Results

"The important message for clinicians is that when you are discussing what to expect after atrial fibrillation ablation with your patients, do not overpromise the results. You can inform them that the success of the procedure depends more on how they perform on the baseline exercise test, and less on the ablation itself," Jaber said.

Clinicians might want to consider advising their patients to become more active and increase their fitness level before undergoing the procedure, but whether doing so will improve outcomes is still unknown.

"This is what we don't know. It makes sense. Hopefully, our results will encourage people to be more active before they arrive here for the procedure," he said. "Our study is retrospective and is hypothesis-generating, but we are planning a prospective study where patients will be referred to cardiac rehab prior to having ablation to try to improve their functional class to see if this will improve outcomes."

Survival of the Fittest

In an accompanying editorial commentary, Eric Black-Maier, MD, and Jonathan P. Piccini Sr, MD, from Duke University Medical Center, Durham, North Carolina, write that the findings have "important implications for clinical practice and raise important additional questions."

They note that catheter ablation as a first-line rhythm-control strategy, per current recommendations, "seems reasonable" in individuals with high baseline cardiorespiratory fitness, but that the benefit is less clear for patients with poor baseline CRF and uncontrolled risk factors.

"Significant limitations in functional status may be at least partially attributable to uncontrolled AF, and patients with limited exercise capacity may stand to gain most from successful catheter ablation," the editorialists write.

"Furthermore, because shorter time from AF diagnosis to catheter ablation has been associated with improved outcomes, the decision to postpone ablation in favor of lifestyle modification is not without potential adverse consequences," they add.

Black-Maier and Piccini agree with the need for additional prospective randomized clinical trials to confirm that exercise training to improve cardiorespiratory fitness before AF ablation is practical and effective for reducing arrhythmia recurrence.

"Over the past 50-plus years, our understanding of cardiorespiratory fitness, exercise capacity, and arrhythmia occurrence in patients with AF continues to evolve," the editorialists conclude. Data from the study "clearly demonstrate that arrhythmia-free survival is indeed survival of the fittest. Time will tell if exercise training and improvements in cardiorespiratory fitness can change outcomes after ablation."

The study was sponsored by the Cleveland Clinic. Jaber and Black-Maier report no relevant financial relationships. Piccini receives grants for clinical research from Abbott, the American Heart Association, the Association for the Advancement of Medical Instrumentation, Bayer, Boston Scientific, and Philips; and serves as a consultant to Abbott, Allergan, ARCA Biopharma, Biotronik, Boston Scientific, LivaNova, Medtronic, Milestone, MyoKardia, Sanofi, Philips, and UpToDate.

Heart Rhythm. Published online August  2, 2020. Abstract, Editorial

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