Improvement in cardiorespiratory fitness (CRF) or weight loss or both resulted in a decrease in atrial fibrillation (AF) burden in obese patients with AF. Rajeev Kumar Pathak, MBBS, Royal Adelaide Hospital, Adelaide, Australia, presented data from the CARDIO-FIT study [Pathak RK et al. J Am Coll Cardiol. 2015].

Weight gain is associated with an increased risk of the development and progression of AF, whereas weight reduction reduces the risk [Pathak RK et al. J Am Coll Cardiol. 2015; Tedrow UB et al. J Am Coll Cardiol. 2010]. In addition, CRF decreases the risk of cardiac death, regardless of a change in body mass index (BMI) [Lee DC et al. Circulation. 2011]. The purpose of the CARDIO-FIT trial was to determine if preserved CRF improved outcomes in obese patients with AF.

In the trial, 308 patients with BMI ≥ 27 kg/m² and AF were enrolled in a structured exercise program and stratified by CRF: low (< 85% predicted), adequate (86% to 100% predicted), and high (> 100% predicted). The exercise program was age and ability matched by metabolic equivalent (MET) and included 3 to 5 days of low- to moderate-intensity aerobic and strength training. Patients exercised for a total of 60 to 200 minutes each week. At baseline, the mean age was 61 years; about half were men; 46% had nonparoxysmal AF; and the mean BMI was 33.2 kg/m².

The primary end points were AF symptom burden as measured by the Atrial Fibrillation Severity Scale questionnaire and freedom from AF as measured by 7-day Holter monitoring. The secondary end points included left atrioventricular and left ventricle thickness, as well as metabolic and inflammatory markers.

CRF was associated with freedom from AF without the use of medication or ablation in a dose-response fashion. When stratified by CRF gain, freedom from AF was achieved in 61% of patients who gained ≥ 2 METs, compared with 18% of patients who gained < 2 METs (P < .001). In addition, arrhythmia-free survival was achieved in 84% of patients with high CRF, compared with 76% and 17% of patients with adequate and low CRF, respectively (P < .001). When stratified by CRF gain, arrhythmia-free survival was achieved in 85% of patients who gained ≥ 2 METs, compared with 44% of patients who gained < 2 METs (P < .001). Weight loss also improved freedom from AF and arrhythmia-free survival regardless of the number of METs gained; however, patients who gained ≥ 2 METs and lost ≥ 10% of their body weight experienced the greatest benefit.

In addition, compared with baseline stress testing, patients who gained CRF demonstrated substantial weight loss, lower systolic blood pressure, reduced use of antihypertensive medications, better diabetes mellitus control with a HbA_1c ≤ 7, lower fasting insulin, lower low-density lipoprotein and triglyceride levels, reduced use of lipid-lowering therapy, and lower mean high-sensitivity C-reactive protein. Furthermore, patients who gained ≥ 2 METs experienced a significant improvement in left atrial volume (P < .001) and left ventricular diastolic function (P < .001) when compared with baseline.

Dr Pathak highlighted that a 1-MET gain in CRF translated into a 12% reduction in AF recurrence risk. In addition, there was a synergistic effect with CRF gain and weight loss.