Prescribing exercise is a viable component of the overall management strategy for achieving rhythm control among overweight and obese patients with atrial fibrillation and may offer benefits beyond weight loss, according to researchers.

“Increased cardiorespiratory fitness was associated with a dose-dependent reduction in AF burden and maintenance of sinus rhythm,” Rajeev K. Pathak, MBBS, and colleagues from the University of Adelaide in Australia reported in the Journal of the American College of Cardiology. “This occurs in conjunction with favorable changes in cardiometabolic risk factor profile, inflammatory state, and cardiac remodeling.”

Exercise is usually recommended for overweight and obese patients with atrial fibrillation (AF) as part of heart rate rhythm control strategies. Research indicates cardiorespiratory fitness (CRF) can predict overall cardiovascular health and outcomes, but no previous studies have examined the effects of physical activity on the recurrence of atrial fibrillation (AF).


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To better understand the interplay among CRF, weight loss, and AF burden, the researchers examined data from 1415 patients with paroxysmal or persistent AF who were referred to the university’s Centre for Heart Rhythm Disorders.

Overall 825 patients had a body mass index >27 kg/m2 and were offered a tailored exercise program and risk factor management intervention. The final analysis included 308 patients who were followed for a mean 49 months. When required, arrhythmia was managed at the discretion of the treating physician through heart rate rhythm control strategies and through ablation. 

Patients participated in a treadmill exercise stress test to determine their CRF level and were categorized into low (mean peak metabolic equivalent [MET] 5.2; n=95), adequate (mean MET 7.9; n=134), and high (mean MET 8.8; n=79) groups at baseline.

Participants were initially advised to take part in 20 minutes of low-intensity exercise 3 times per week, which was later escalated to at least 200 minutes of moderate-intensity exercise per week. All participants wore a heart monitor, and kept a log of diet and physical activity.

The researchers then measured changes in CRF, weight loss, and AF burden on the AF Severity Scale (AFSS). Participants were then split into two CRF groups – <2 MET gain (n=181) and ≥2 MET gain (n=127). Overall CRF gains among the two groups during the study period was 2.9 in the ≥2 MET group vs 0.5 in the <2 MET group, respectively (P<.001). Greater MET gains corresponded with higher participation in the dedicated risk factor management clinic – 83% vs 39% (P<.001).

At final follow-up, participants in the high CRF group had higher rates arrhythmia-free survival both with and without the use of rhythm control strategies (P<.001 for both), the researchers found. Total arrhythmia-free survival rates were 17% in the low, 76% in the adequate, and 84% in the high cardiorespiratory fitness groups (P<.001). Furthermore 12% of the low, 35% of the adequate, and 66% of the high cardiorespiratory fitness group (P<.001) remained free from arrhythmia without antiarrhythmic drugs or ablation.

“Indeed, 61% of previously symptomatic AF patients no longer required antiarrhythmic medications or ablation,” the researchers wrote.

Participants who gained ≥2METs experienced significant decreases in AF burden and symptom severity as measured on the AFSS compared with those in the <2 METs group and had higher rates of arrhythmia-free survival (P<.001 for all).

Each unit increase in METs from baseline cardiorespiratory fitness was associated with a 13% decline in AF recurrence risk without the use of ablation or medications.

Among patients who underwent rhythm control strategies in addition to the study intervention, there was a 20% reduction in total arrhythmia recurrence with each additional MET achieved from baseline cardiorespiratory fitness levels (HR: 0.80; 95% CI: 0.74 to 0.87; P<0.001).  This finding indicates a dose-response relationship between cardiorespiratory fitness and the risk for atrial fibrillation.

In addition to improving AF outcomes, patients in the higher METs group experienced greater improvements in weight loss, blood pressure control, lipid profiles, glycemic control, and markers of inflammation.

The benefits from CRF gains were independent of those conferred by weight loss alone, the researchers emphasized. “The seminal finding that the change in [CRF] over a follow-up period reduces AF recurrence supports a possible role for the prescription of exercise in this cohort,” the researchers wrote.

They called for additional research to understand the mechanisms of how CRF reduces the risk of AF and to clarify whether certain methods to maintain CRF are more effective than others for overweight and obese patients.

Reference

  1. Pathak RK et al. Impact of CARDIOrespiratory FITness on Arrhythmia Recurrence in Obese Individuals With Atrial Fibrillation. J Am Coll Cardiol. 2015. doi:10.1016/j.jacc.2015.06.488.