Atrial fibrillation (AF) is increasingly being viewed by clinicians as a modern-day epidemic, affecting more than 2.2 million adults in the United States. AF is strongly age-dependent, affecting 4% of people older than 60 and 8% of those older than 80. Alarmingly, about one-quarter of people aged 40 and older are expected to develop AF during their lifetime. Another growing problem is the continued emergence of metabolic syndrome (MS), which is estimated to affect 21% to 24% of U.S. adults.

Coexistence of MS and AF is common. Studies suggest that different components of MS, including hypertension, diabetes, dyslipidemia, and obesity, increase the likelihood of AF. Catheter ablation has been a major treatment advance for the condition, offering a new spectrum of options for drug-refractory AF patients. However, this procedure is yet to be a total success in maintaining long-term sinus rhythm, even in the best hands. Little is known about the role of MS on the long-term outcome of AF ablation, such as restoration of sinus rhythm and improvement in quality of life (QOL).

Taking a Deeper Look at Atrial Fibrillation

In the April 3, 2012 Journal of the American College of Cardiology, we had a study published that prospectively analyzed 1,496 patients with AF who were undergoing a first ablation. About 45% of our study group had long-standing persistent AF, while 29% had paroxysmal AF and 26% had persistent AF. Patients were classified as either having MS or not having MS. They were followed for AF recurrence and QOL at 12 months after their ablation procedure.

At follow-up, 39% of patients with MS had experienced arrhythmia recurrence, compared with 32% of patients without MS. When we stratified patients by AF type, findings among patients with non-paroxysmal AF were the most pronounced. Non-paroxysmal AF patients with MS were more likely to fail to get their arrhythmia under control when compared with those without MS (46% vs 35%). In patients with non-paroxysmal AF, the following were identified as independent predictors of recurrence: • MS. • C-reactive protein of 0.9 mg/dl or higher. • Sex. • White blood cell count. However, we did not observe a significant difference in the subgroup of patients with paroxysmal AF (25% vs 22%).

Metabolic Syndrome: Piecing it Together

Our study offers valuable insights for clinicians managing these patients. It appears that patients with MS have a higher prevalence of non-pulmonary vein triggers when compared to the general population. This is why pulmonary vein isolation alone has poor outcomes in patients with MS. Baseline inflammatory markers and the presence of MS appeared to predict higher AF recurrence after single-catheter ablation only in patients with non-paroxysmal AF. We also observed significant improvements in QOL after an ablation procedure in patients with MS after they underwent their procedure. Clinicians should consider these factors and pay close attention to MS and other comorbidities before offering ablation procedures for AF. Ideally, more studies will emerge to help us optimize outcomes in this growing patient population.