Higher baseline cardiorespiratory fitness (CRF) is associated with better outcomes after atrial fibrillation (AFib) ablation, according to new research.
In a single-center, retrospective cohort study, patients with the highest level of baseline CRF had significantly lower rates of arrhythmia recurrence and death than did patients with lower levels of CRF.
“It is stunning how just a simple measure, in this case walking on a treadmill, can predict whether atrial fibrillation ablation will be a successful endeavor or if it will fail,” senior author Wael A. Jaber, MD, professor of medicine, Cleveland Clinic, said in an interview.
“We found that ablation was not successful in most patients who had poor functional class and, conversely, that it was successful in most patients who were in tip-top shape when they walked on the treadmill. Our results can help clinicians inform patients about what they can expect after the procedure, depending on the baseline fitness level,” Dr. Jaber said.
The study was published online Aug. 2 in Heart Rhythm.
Several studies have shown a reduction in AFib incidence among individuals who report a physically active lifestyle, but the extent to which baseline CRF influences arrhythmia rates after AFib ablation is unknown, the authors note.
For the study, Dr. Jaber and colleagues analyzed results in 591 consecutive patients (mean age, 66.5 years; 75% male) with symptomatic paroxysmal or persistent AFib who underwent de novo AFib ablation at their institution. Only patients who had undergone an exercise stress test in the 12 months before AFib ablation (average, 4.5 months) were included.
Age- and sex-specific predicted metabolic equivalents (METs) were calculated using the St. James model for women and the Veterans Affairs referral model for men. The number of METs achieved was then divided by the predicted METs, and the patients were categorized into low (<85% predicted; n = 152), adequate (85%-100% predicted; n = 115), and high (>100% predicted; n = 324) CRF groups. Functional capacity was characterized as poor in 56 patients (9.5%), fair in 94 (16.0%), average in 225 (38.1%), good in 169 (28.6%), and high in 47 (8.0%).
During a mean follow-up of 32 months, arrhythmia recurrence was observed in 79% of patients in the low-CRF group, 54% of patients in the adequate-CRF group, and 27.5% of patients in the high-CRF group (P < .0001). Rates of repeat arrhythmia-related hospitalization, repeat rhythm-control procedures, and the need for ongoing antiarrhythmic therapy (ATT) were significantly lower in the high-CRF group. Specifically, ATT was stopped in 56% of patients in the high-CRF group, compared with 24% in the adequate-CRF group and 11% in the low-CRF group (P < .0001). Rehospitalization for arrhythmia was required in 18.5%, 38.0%, and 60.5% of cases, respectively, and repeat direct-current cardioversion or ablation was performed in 26.0%, 49.0%, and 65.0%, respectively (P < .0001 for both).
Death occurred in 11% of the low-CRF group, compared with 4% in the adequate-CRF group and 2.5% in the high-CRF group. Most (70%) of the deaths were caused by cardiovascular events, including heart failure, cardiac arrest, and coronary artery disease. The most common cause of noncardiac death was respiratory failure (13%), followed by sepsis (10%), malignancy (3%), and complications of Parkinson’s disease (3%).
“Although there was a statistically significant association between higher CRF and lower mortality in this cohort, the findings are to be viewed through the prism of a small sample size and relatively low death rate,” the authors wrote.