Impact of CARDIOrespiratory FITness on Arrhythmia Recurrence in Obese Individuals with Atrial Fibrillation: The CARDIO-FIT Study. RK Pathak et al.
Journal of the American College of Cardiology (2015), doi: 10.1016/j.jacc.2015.06.488.
Obesity has been recognised as a risk factor for atrial fibrillation (AF). Lifestyle modification including weight-loss has been shown to reduce the burden of AF in obese patients.
The paper of Pathak et al. investigates the impact of cardiorespiratory fitness at baseline and fitness gain after a structured exercise program on AF burden in obese patients with a history of AF, treated with antiarrhythmic medication or AF ablation.
Out of 1415 consecutive patients with AF, 825 (58%) had a body mass index≥27 kg/m2, and 308 were included in the analysis. Exercise testing was performed using Bruce protocol. Metabolic equivalents (MET), and MET gain was calculated. Fitness gain was dichotomized in METs gain≥2 and <2. A structured exercise program was offered, starting with low-intensity (20 min thrice-weekly) which was increased to >200 min moderate-intensity exercise/week. Goal-directed weight and risk factor management was performed. AF burden was assessed by 7-day Holter monitoring.
Freedom of AF was greatest in patients with high (>100%) fitness compared to adequate (86-100%) or low fitness (<85%). AF burden decreased significantly in the group with fitness gain ≥2 METs as compared to <2 METs group. Freedom of AF was greatest in those with METs gain ≥2 compared to those with METs gain <2. In multivariable analyses, baseline cardiorespiratory fitness, fitness gain and weight-loss were independent predictors of outcomes. METs gain ≥2 in fitness resulted in a 2-fold greater probability of arrhythmia-free survival.
The novelty of the study is the observation that in addition to weight-loss, cardiorespiratory fitness and fitness gain are independent predictors of arrhythmia-free survival in obese patients with AF. The authors provided some plausible explanations for the inverse association of fitness gain and AF burden. Patients who gained more than 2 METs had a greater decline in blood pressure, a better lipid profile and glycaemic control, a lower high-sensitivity c-reactive protein, a greater decline in left atrial volume, left ventricular diameter and E/E’. Fitness gain is a surrogate of an effective exercise training. The positive effects of exercise on inflammation, insulin sensitivity, and vascular resistance may have contributed to the improvements in left atrial and ventricular geometry, diastolic function, and ventricular filling pressures. All together this may have prevented a progressive atrial remodeling, reflected by a lower burden of AF.
The study highlights the fact that lifestyle interventions have a major impact on the outcome after most cardiovascular interventions and should be an indispensable part of treatment.
EACPR Exercise, Basic and Translational Research Section
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