Cardiorespiratory fitness may predict arrhythmia recurrence in obese individuals with symptomatic atrial fibrillation (AFib), according to results of the CARDIO-FIT study, presented June 22 as a Late-Breaking Clinical Trial at EHRA EUROPACE – CARDIOSTIM 2015 in Milan, Italy, and simultaneously published in the Journal of the American College of Cardiology.

The study was led by Rajeev K. Pathak, MBBS, of the Centre for Heart Rhythm Disorders, South Australian Health and Medical Research Institute, University of Adelaide and Royal Adelaide Hospital, Adelaide, Australia, and analyzed 308 patients with AFib and a body mass index ≥ 27 kg/m2 who underwent exercise stress testing to determine peak metabolic equivalents (METs). Cardiorespiratory fitness was categorized as low (< 85 percent), adequate (86 – 100 percent) and high (> 100 percent), and impact of cardiorespiratory fitness gain was determined by the objective gain in the fitness at final follow-up (≥ 2 METs vs. < 2 METs). AFib rhythm control was determined using a seven-day Holter monitoring and AFib severity scale questionnaire.

Results showed that arrhythmia-free survival with and without rhythm control strategies was greatest in patients with high cardiorespiratory fitness compared to adequate or low cardiorespiratory fitness (p<0.001 for both). The authors also found a "significant dose-response relationship between baseline cardiorespiratory fitness with a 20 percent reduction in the risk of AFib recurrence for each MET increase in baseline cardiorespiratory fitness." Further, "MET gain in cardiorespiratory fitness ≥ 2 on top of weight-loss was associated with two-fold greater freedom from AFib."

The authors conclude that "cardiorespiratory fitness gain provides a 12 percent incremental gain over weight-loss in long-term freedom from total AFib burden. This occurs in conjunction with favorable changes in cardiometabolic risk factor profile, inflammatory state and cardiac remodeling." They add that "these findings highlight the prescriptive role of exercise in managing patients with AFib, particularly as a strategy for rhythm control."

Keywords: Atrial Fibrillation, Body Mass Index, Cost of Illness, Electrocardiography, Ambulatory, Exercise, Follow-Up Studies, Metabolic Equivalent, Obesity, Overweight, Surveys and Questionnaires, Risk Factors, Weight Loss

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