Cardiorespiratory fitness improvements reduce risk of atrial fibrillation

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Obese individuals with atrial fibrillation had a decreased risk of arrhythmia recurrence if they improved their cardiorespiratory fitness, according to an Australian observational study. The researchers found a gain in cardiorespiratory fitness provided a 12 percent incremental improvement over weight loss in long-term freedom from atrial fibrillation.

In addition, there was a 20 percent reduction in the risk of atrial fibrillation recurrence for each metabolic equivalent (MET) increase in baseline cardiorespiratory fitness. Patients who had at least a two MET increase had a two-times greater freedom from atrial fibrillation.

Lead researcher Rajeev K. Pathak, MBBS, of the Centre for Heart Rhythm Disorders at the University of Adelaide, and colleagues published their results online in the  Journal of the American College of Cardiology on Aug. 24.

“Cardiorespiratory fitness gain with a structured exercise program has an additive effect to weight loss in improving the long-term outcomes of [atrial fibrillation],” they wrote.

Previous research showed losing weight reduces the burden of atrial fibrillation, which affects approximately 33.5 million people worldwide. Although improvements in cardiorespiratory fitness has been shown to lower the risk of all-cause and cardiovascular mortality, the researchers noted that healthcare professionals usually do not target combining cardiorespiratory fitness with weight loss to improve atrial fibrillation outcomes.

This analysis included 308 patients who were referred for management of symptomatic paroxysmal or persistent atrial fibrillation at the University of Adelaide. At baseline, all patients had a body mass index of at least 27 kg/m 2 and underwent an exercise stress test.

During their initial assessment, patients had the option to attend a physician-led risk factor management clinic that promoted graded exercise therapy and weight reduction through a meal plan and behavior modification. The exercise program varied among patients and was tailored based on their age and physical ability.

The researchers evaluated cardiorespiratory fitness using sex-specific METs from a treadmill exercise test. They then categorized patients into three groups: low (less than 85 percent predicted METs), adequate (86 percent to 100 percent predicted METs) and high (more than 100 percent METs).

At baseline, 95 patients had low cardiorespiratory fitness, 134 had adequate cardiorespiratory fitness and 79 had high cardiorespiratory fitness.

After a mean follow-up of 49 months, 12 percent of the low, 35 percent of the adequate and 66 percent of the high group remained free from arrhythmia without taking antiarrhythmic drugs or undergoing ablation.

The total arrhythmia-free survival rates were 17 percent in the low, 76 percent in the adequate and 84 percent in the high groups.

“While weight loss is important for heart disease patients, especially those with arrhythmia, our study shows it's beneficial to have high cardiorespiratory fitness and continue to improve on that,” senior study author Prashanthan Sanders, MBBS, PhD, said in a  news release. “An ideal treatment plan would include a focus on both.”