BOSTON– The already-firm evidence implicating obesity in boosting both the incidence and severity of atrial fibrillation grew even stronger with results from four meta-analyses that comprised 51 controlled studies involving a total of more than 600,000 people.
“We should pay more attention to using weight reduction strategies to prevent AF [atrial fibrillation] and to reduce its burden in patients with obesity and established AF,” Dr. Dennis H. Lau said at the annual scientific sessions of the Heart Rhythm Society.
Mitchel L. Zoler/Frontline Medical News
Dr. Christine M. Albert
Physicians are increasingly aware of the strong evidence linking obesity and atrial fibrillation incidence and severity, said Dr. Christine M. Albert, director of the Center for Arrhythmia Prevention at Brigham and Women’s Hospital, Boston. The existence of this link is “really important because it is something we can offer patients,” Dr. Albert said in an interview. Obesity interventions provide a way to intervene in patients with, or at risk for, atrial fibrillation that goes beyond atrial ablation and antiarrhythmic drugs to reduce symptoms and help patients feel better, she noted.
Dr. Lau and his associates reviewed the published medical literature through January 2012 and identified 51 studies that examined the link between obesity and AF in a total of 626,603 people.
They found 16 studies with 5,864 patients that assessed the link between obesity and AF recurrence following atrial ablation treatment and found a statistically significant 13% increased rate of recurrent AF for every 5-unit rise in body mass index, Dr. Lau reported.
Mitchel L. Zoler/Frontline Medical News
Dr. Dennis H. Lau
They also identified 12 studies on the impact of obesity in 62,160 patients who underwent cardiac surgery that collectively showed a statistically significant 10% higher incidence of postoperative AF for every additional 5 BMI units.
The researchers found nine studies of the role of obesity in new-onset AF in cohort analyses with a total of 157,518 patients that showed an overall, statistically significant 29% rise in AF incidence for every 5 additional BMI units. And in 14 case-control studies with 401,061 patients, the rate of new-onset AF increased by a statistically significant 19% for every 5-unit rise in BMI.
These findings fit into an already substantial body of evidence documenting a significant link between obesity and AF, said Dr. Lau, director of the cardiac pacing unit at the Royal Adelaide (Australia) Hospital. For example, an analysis of 14,598 Americans enrolled in the Atherosclerosis Risk in Communities (ARIC) study found that 18% of the 1,520 new cases of AF that occurred in this cohort during an average 17 years of follow-up could be attributed to obesity or overweight (Circulation 2011;123:1501-8). Data collected from 34,309 women enrolled in the Women’s Health Study who had 834 cases of incident AF during an average 13-year follow-up showed that every 1-unit increase in BMI was linked to a 5% increased risk for AF, and that obese women had an overall 65% higher incidence of AF than did women with a normal BMI (J. Am Coll. Cardiol. 2010;55:2319-27).
And Dr. Lau and his associates recently published a review of 355 patients with AF and a baseline BMI of at least 27 kg/m2 who participated in a weight-management program. After 5 years, patients who lost at least 10% of their baseline weight had an 86% rate of arrhythmia-free survival, compared with a 40% rate in patients who either lost less than 3% of their baseline weight or gained weight. In a multivariate analysis, weight loss of at least 10% linked with a statistically significant sixfold increase in arrhythmia-free survival, compared with all the other patients in the analysis (J. Am. Coll. Cardiol. 2015;65:2159-69).
Dr. Lau also cited findings from animal studies by his group that point to a direct role for obesity, and specifically deposits of epicardial fat in causing AF. Their model uses overfed sheep, and his group found that a higher burden of epicardial fat leads to fat infiltration into the myocardium, including atrial tissue. “We postulate that this fat contributes to conduction heterogeneity, increased re-entry, increased susceptibility to AF, and increased duration of AF episodes,” he said.
“It’s quite clear that obesity itself is important because, for example, the sheep do not develop sleep apnea, and they have only marginally elevated blood pressures. Using this animal model, we are quite convinced that obesity itself is an important risk factor.”
Dr. Lau added that results from recent sheep studies showed that after previously obese sheep lose their excess weight their atrial abnormalities revert to normal.