Atrial fibrillation and metabolic syndrome

AUSTIN, TEXAS. Metabolic syndrome (MS) combines a cluster of cardiovascular risk factors including obesity, hypertension, diabetes, and dyslipidemia as indicated by a HDL (high-density lipoprotein) level of less than 40 mg/dL for men and less than 50 mg/dL for women and a serum triglyceride level of 150 mg/dL or higher. Both MS and atrial fibrillation (AF) involve systemic inflammation, so it is not surprising that the two conditions often coexist. It is also not surprising that MS and AF both are associated with an often vastly diminished quality of life (QoL). A team of electrophysiologists from the USA, China, and Italy set out to determine the impact of radiofrequency catheter ablation on AF recurrence and QoL in AF patients with and without comorbid MS.

The study involved 485 patients with AF and MS (average age of 64 years, 77% men, 32% paroxysmal) and 1010 AF patients without MS (average age of 62 years, 72% men, 28% paroxysmal). Both groups had elevated levels of the inflammation marker C-reactive protein (CRP) and white blood cells (WBC), with the levels being significantly higher in the MS group. As expected, hypertension, diabetes, obesity and dyslipidemia were more prevalent in the MS group, as was the incidence of coronary artery disease, heart failure and left atrium enlargement.

The Medical Outcomes Study SF-36 Health Survey was used to assess QoL at baseline and 12 months after ablation. The SF-36 Survey measures two composite scores – the mental health component summary (MCS) covering such aspects as vitality, social functioning, role limitations due to emotional problems and mental health, and the physical health component summary (PCS) which includes such aspects as physical functioning, role limitations due to physical health, bodily pain and general well-being.

All study participants underwent a single standard pulmonary vein isolation procedure with additional lesions as required. After a 21-month follow-up, 39% of the members of the AF/MS group had experienced arrhythmia recurrence as compared to 32% in the AF only group. The main predictors of AF recurrence in patients with non-paroxysmal AF (persistent and permanent) were the presence of MS (a 42% relative risk increase), female sex (a 28% relative risk increase), elevated CRP (an 87% relative risk increase if over 0.9 mg/dL), and an elevated WBC count. The above factors did not predict risk of recurrence in patients with paroxysmal AF. The main procedure-related complication was pericardial effusion, which occurred in 11 patients (0.7%).

Quality of Life scores were significantly lower at baseline for the AF/MS group than for the AF alone group. However, both the MCS and PCS scores improved significantly in the AF/MS group following a successful ablation. MCS increased by 5.7 points and PCS increased by 9.1 points. In the AF alone group only MCS improved (by 4.6 points).

The authors of the study speculate that the poorer outcome for AF/MS patients is related to increased inflammation and increased structural remodelling as expressed by left atrium enlargement and increased atrial fibrosis. Fibrosis leads to the separation of myocytes (heart cells) from one another, which significantly impairs the transmission of electrical signals at the cellular level and results in chaotic atrial conduction.
Mohanty, S, Natale, A, et al. Impact of metabolic syndrome on procedural outcomes in patients with atrial fibrillation undergoing catheter ablation. Journal of the American College of Cardiology, Vol. 59, No. 14, April 3, 2012, pp. 1295-301
Asirvatham, SJ and Jiao, Z. What causes atrial fibrillation and why do we fail with ablation? Journal of the American College of Cardiology, Vol. 59, No. 14, April 3, 2012, pp. 1302-03

Editor’s comment: Apart from confirming that a combination of AF and MS makes for a pretty miserable quality of life, this study once again concludes the negative consequences of going into an ablation with an elevated level of systemic inflammation. Inflammation can be reliably reduced by supplementation with such natural anti-inflammatories as vitamin C, fish oil, Zyflamend, curcumin, beta-sitosterol and Boswellia.