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CARDIO-FIT: High cardiorespiratory fitness protects against AF recurrence in patients with obesity
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In patients with obesity and atrial fibrillation, high cardiorespiratory fitness was associated with a higher rate of arrhythmia-free survival and reduced atrial fibrillation burden and symptom severity, according to the results of the CARDIO-FIT study.
Previous research showed that obesity is a predictor of AF and increased cardiorespiratory fitness protects against incident AF in people with obesity, but the effect of cardiorespiratory fitness on AF recurrence was not known, according to the study background.
Rajeev K. Pathak
Rajeev K. Pathak, MBBS, and colleagues analyzed 308 patients with AF and BMI of at least 27 kg/m2. All patients underwent exercise stress testing at baseline to determine peak metabolic equivalents (METs). They were stratified into three groups based on level of cardiorespiratory fitness: high (> 100%; mean MET, 8.8), adequate (86% to 100%; mean MET, 7.9) or low (≤ 85%; mean MET, 5.2).
The researchers assessed cardiorespiratory fitness gain by objective gain in fitness at final follow-up (≥ 2 METs vs. < 2 METs) and determined AF rhythm control via 7-day Holter monitoring and an AF severity scale questionnaire. Mean follow-up was 49 months.
Fitness predicted AF recurrence
At final follow-up, 66% of those in the high cardiorespiratory fitness group were free from arrhythmia without antiarrhythmic drugs or ablation vs. 35% from the adequate group and 12% from the low group (P < .001).
Univariate predictors of AF recurrence were cardiorespiratory fitness group (P < .001), no weight loss (P = .001) and left ventricular hypertrophy (P = .05), whereas in a multivariable analysis, low cardiorespiratory fitness was an independent predictor of AF recurrence compared with high cardiorespiratory fitness (HR = 2.75; 95% CI, 1.61-4.68) and adequate cardiorespiratory fitness (HR = 1.89; 95% CI, 1.14-3.12), according to the researchers. No weight loss remained an independent predictor for recurrent AF (HR = 2.95; 95% CI, 1.8-4.8), and each unit increase in MET of baseline cardiorespiratory fitness was associated with a 13% decline in risk for AF recurrence, even after adjusting for weight loss at follow-up (HR = 0.87; 95% CI, 0.8-0.94).
Total arrhythmia-free survival was 17% in the low group, 76% in the adequate group and 84% in the high group (P < .001), and on multivariable analysis, independent predictors of total AF recurrence were low cardiorespiratory fitness (HR compared with high cardiorespiratory fitness = 5.94; 95% CI, 3.15-11.23) and no weight loss (HR = 3.64; 95% CI, 1.95-6.76), the researchers wrote. Each unit increase in MET of baseline cardiorespiratory fitness was associated with a 20% decline in risk for total AF recurrence, even after adjusting for weight loss at follow-up (HR = 0.8; 95% CI, 0.74-0.87).
Fitness gain beneficial
Those with cardiorespiratory fitness gain of at least 2 METs had a greater decrease in AF burden and symptom severity compared with those with cardiorespiratory fitness gain of less than 2 METs (P < .001), as well as a higher rate of arrhythmia-free survival with and without rhythm control (P < .001 for both).
In multivariable analyses, baseline cardiorespiratory fitness (P < .001), cardiorespiratory fitness gain (P < .001) and weight loss (P = .008) were independent predictors of outcomes, and those with cardiorespiratory fitness gain of at least 2 METs had a twofold (95% CI, 3.4-10.3) greater probability of arrhythmia-free survival.
All patients were offered participation in a dedicated risk factor management clinic; those who accepted the offer were more likely to have increased cardiorespiratory fitness gain, the researchers wrote.
“These findings highlight the prescriptive role of exercise in managing patients with AF, particularly as a strategy for rhythm control,” Pathak, from the Centre for Heart Rhythm Disorders, South Australian Health and Medical Research Institute, University of Adelaide and Royal Adelaide Hospital, Australia, and colleagues wrote.
The results were presented as a late-breaking clinical trial at the EHRA Europace-Cardiostim 2015 meeting in Milan. – by Erik Swain
Disclosure: Two researchers report financial ties with Biosense Webster, Boston Scientific, Medtronic, Sorin and St. Jude Medical.
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