Impact of CARDIOrespiratory FITness on Arrhythmia Recurrence in Obese Individuals With Atrial Fibrillation: The CARDIO-FIT Study.

BACKGROUND Obesity begets atrial fibrillation (AF). Although cardiorespiratory fitness is protective against incident AF in obese individuals, its effect on AF recurrence or the benefit of cardiorespiratory fitness gain is unknown. OBJECTIVES This study sought to evaluate the role of cardiorespiratory fitness and the incremental benefit of cardiorespiratory fitness improvement on rhythm control in obese individuals with AF. METHODS Of 1,415 consecutive patients with AF, 825 had a body mass index ≥27 kg/m(2) and were offered risk factor management and participation in a tailored exercise program. After exclusions, 308 patients were included in the analysis. Patients underwent exercise stress testing to determine peak metabolic equivalents (METs). To determine a dose response, cardiorespiratory fitness was categorized as: low (<85%), adequate (86% to 100%), and high (>100%). Impact of cardiorespiratory fitness gain was ascertained by the objective gain in fitness at final follow-up (≥2 METs vs. <2 METs). AF rhythm control was determined using 7-day Holter monitoring and AF severity scale questionnaire. RESULTS There were no differences in baseline characteristics or follow-up duration between the groups defined by cardiorespiratory fitness. 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). AF burden and symptom severity decreased significantly in the group with cardiorespiratory fitness gain ≥2 METs as compared to <2 METs group (p < 0.001 for all). Arrhythmia-free survival with and without rhythm control strategies was greatest in those with METs gain ≥2 compared to those with METs gain <2 in cardiorespiratory fitness (p < 0.001 for both). CONCLUSIONS Cardiorespiratory fitness predicts arrhythmia recurrence in obese individuals with symptomatic AF. Improvement in cardiorespiratory fitness augments the beneficial effects of weight loss. (Evaluating the Impact of a Weight Loss on the Burden of Atrial Fibrillation [AF] in Obese Patients; ACTRN12614001123639).