CARDIO-FIT: Increased Fitness Linked to Dose-Dependent Reduction in Atrial-Fibrillation Symptoms, Recurrence

Deborah Brauser

June 23, 2015

MILAN, ITALY — More research suggests beneficial effects from lifestyle changes. This time, cardiorespiratory fitness (CRF) was shown to help not only with relieving symptoms of atrial fibrillation (AF), but it also predicted recurrence in patients who were obese[1].

The Cardiorespiratory Fitness on Arrhythmia Recurrence in Obese Individuals with Atrial Fibrillation (CARDIO-FIT) observational study of 308 patients showed that those who had high CRF at baseline were significantly more likely to have arrhythmia-free survival at follow-up more than 4 years later than the participants who had low or even adequate cardiofitness.

After patients enrolled in a tailored exercise program, both CRF fitness gain and weight loss were associated with significantly improved outcomes. In addition, the patients who gained at least two peak metabolic equivalents (METs) had a greater decrease in AF burden and symptom severity and more incidence of arrhythmia-free survival with or without rhythm control vs those with fewer METs gained—and a twofold greater probability of arrhythmia-free survival.

The results were presented at a late-breaking clinical-trial session here at the European Heart Rhythm Association (EHRA) EUROPACE-CARDIOSTIM 2015 meeting and were simultaneously published in the Journal of the American College of Cardiology.

"This study emphasizes the prescriptive role of exercise in managing patients with afib, particularly in a strategy of rhythm control," lead author Dr Rajeev Pathak (University of Adelaide and Royal Adelaide Hospital, Australia) told meeting attendees.

Pathak noted to heartwire from Medscape that the take-away message is that baseline CRF has a dose-dependent effect on AF long term. "The findings really show the importance of exercise to atrial fibrillation."

Synergistic Effect?

Dr Rajeev Pathak

As reported by heartwire , Pathak and colleagues presented results from the LEGACY trial earlier this year at the American College of Cardiology (ACC) 2015 Scientific Sessions, which examined the impact of weight loss on patients with AF.

For the new study, the investigators wanted to assess whether CRF could offset detrimental effects of obesity in patients with AF and whether increasing fitness had a "synergistic effect" with weight loss.

Of the 308 patients included in the CARDIO-FIT analysis, 95 were considered to have low CRF at baseline (46% men; mean age 58 years; body-mass index [BMI] 34.0), 134 had adequate CRF (64% men; mean age 56 years; BMI 32.7), and 79 had high CRF (40% men; mean age 69 years; BMI 32.8).

All participants were entered into a tailored exercise program that matched their individual age and ability and included both aerobic and strength training. The sessions occurred 3 to 5 days per week for a total of 60 to 200 minutes/week.

The two primary outcomes were AF symptom burden, as measured with the AF severity scale, and AF freedom, defined as being free from arrhythmia without the use of ablation or antiarrhythmic drugs, which was measured with 7-day Holter monitoring.

AF freedom at the final follow-up of 1825 days was achieved by 66% of the high-CRF group vs 35% of the adequate group and only 12% of the low group ( P<0.001). Total arrhythmia-free survival rates at the same time-point were 84%, 76%, and 17%, respectively (P<0.001).

Significant predictors of AF recurrence included being in the low-CRF group (hazard ratio [HR] 2.75; 95% CI 1.61–4.68) or in the adequate group (HR 1.89; 95% CI 1.14–3.12), as well as not achieving any weight loss (HR 2.95; 95% CI 1.8–4.8).

Improved Fitness, Improved Outcomes

To examine impact of CRF gain, all participants underwent an exercise stress test at baseline as well as at follow-up a mean of 48 months later. A total of 127 of the patients achieved a MET gain of at least 2, while the remaining 181 did not.

Interestingly, "each unit increase in MET of baseline [CRF] was associated with a 12% decline in the risk of AF recurrence, even after adjusting for weight-loss during follow-up" (HR 0.87, 95% CI 0.80–0.94; P<0.001), report the investigators, adding that there was a 20% decline in total arrhythmia recurrence for each MET-unit increase.

At final follow-up, freedom from arrhythmia without drugs or ablation was sustained by 61% of the patients who gained at least 2 METs vs just 18% of those with fewer METs gained; total arrhythmia-free survival was sustained by 85% and 44%, respectively.

Finally, 75.6% of the patients who had at least 10% weight loss and at least 2 METs gained were AF free without drugs or ablation at final follow-up vs 13.2% of those who did not achieve either of these measures (P<0.001). Total arrhythmia-free survival was achieved by 94% and 34% of the two groups, respectively.

Pathak added that there has been a lot of debate as to whether weight loss or exercise is more important when it comes to AF management. "We have shown weight loss is important and now exercise is as well. If you ask me, they complement each other," he said.

"Spectacular Data"

Session moderator Dr Claudia Herrera Siklódy (Klinikum Ludwigsburg, Germany) called this "very, very interesting data" for an already-overweight patient population.

"Just by doing cardiorespiratory training, the data were spectacular. But if you combine that with our other strategies, it's even better. And I think that might be the most interesting part of this paper—it combines our strategies for treating the illness that is already there with upstream therapy to try to prevent it," said Siklódy.

She noted that she and her colleagues published a paper in 2013[2] showing that overweight patients with AF have higher levels of inflammation markers and a study in 2009 showing that these markers have a significant impact on ablation recurrence.

"The study from Adelaide fits in very well with these findings. It's important to tell our afib patients that this does not just end with ablation, it's a disease that goes on and on if you are not fighting against it," said Siklódy.

"Lifestyle changes, according to all of this data, are very important. Unfortunately, they are very hard to implement and maintain. So we need to communicate much better with our patients," she said, adding that perhaps prevention programs should aim toward young and healthy patients, "when they are more open to make changes to their way of life."

The study was funded by the Center for Heart Rhythm Disorders at the University of Adelaide. Pathak reports being supported by a postgraduate scholarship from the Lion's Medical Research Foundation and by an Australian Postgraduate Award and Leo J Mahar Electrophysiology Scholarships from the University of Adelaide. Disclosures for the coauthors are listed in the article. Siklódy reported receiving speaking fees from Biosense Webster and St Jude Medical.

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