Bariatric Surgery and the Risk of New-Onset Atrial Fibrillation in Swedish Obese Subjects

Jamaly S, Carlsson L, Peltonen M, et al.
J Am Coll Cardiol 2016;68:2497–504

Background

Obesity is a risk factor for atrial fibrillation (AF), and the increased morbidity and mortality of obese individuals may be partially explained by AF [1-3]. Hence, significant weight reduction through bariatric surgery, might contribute to the reduction of the risk of new-onset AF in these patients [4]. In contrast to lifestyle interventions, bariatric surgery results in large weight losses able to be maintained over time.

In this analysis, the association between bariatric surgery and the incidence of AF was evaluated, using data from the Swedish Obese Subjects study (SOS) [5]. The cohort was recruited between 1987 and 2001 and comprised 4021 obese individuals with sinus rhythm and no history of AF. Of these, 2000 underwent bariatric surgery (surgery group).

Main results

• The 2 study groups were fairly well balanced, although BMI was higher and several cardiovascular risk factors were less favourable in the surgery group.
• During a median follow-up of 19 years, new-onset AF occurred in 12.4% patients in the surgery group and in 16.8% patients in the control group.
• Patients who underwent bariatric surgery had a 29% lower risk for new-onset AF compared with patients in the control group (HR: 0.71; 95% CI: 0.60 - 0.83; P < 0.001).
• After multivariable adjustments, weight loss by bariatric surgery remained associated with reduced incidence of AF (adjusted HR: 0.69; 95% CI: 0.58 - 0.82; P < 0.001).
• Baseline characteristics that were independently associated with an increased risk of AF included advancing age, greater height, increasing BMI, hypertension, increasing thyroxin levels, and higher alcohol intake.
• There were no significant interactions between treatment and subgroups, with the exception of age and diastolic blood pressure (DBP): younger individuals benefitted more from surgery compared with those who were older (P interaction = 0.001), and patients with high DBP benefitted more from surgery compared with those who had low DBP (P interaction = 0.028).

Conclusion

Weight loss by bariatric surgery in severely obese individuals was associated with a reduced incidence of new-onset AF during long-term follow-up. The benefit was higher in younger individuals and in those with higher blood pressure. These data support the hypothesis that bariatric surgery is likely to decrease AF-related CV morbidity and mortality.

Editorial comment [6]

In their editorial article, Kalman, Nalliah, and Sanders note that the two study groups were not well balanced, since the patients who underwent bariatric surgery were younger and had more CV and AF risk factors. The study included a selected population, with most individuals free from AF at baseline. AF was not a predefined endpoint of the study, and potential mechanisms for the association between weight loss and lower rates of incident AF were not explored.
The authors of the editorial conclude: ‘Despite the limitations of a population-based observational study, Jamaly et al. make a simple but potent point. Although weight loss may curtail rates of incident AF in obese populations weight loss must be substantial and sustained. This study provides important preliminary data supporting electrophysiological benefit for weight loss in non-AF populations. The data are entirely consistent with existing literature at both epidemiological and mechanistic levels, and extends existing data from secondary to primary prevention contexts. However, further studies are required to define the categories of baseline weight that would most benefit from weight loss, quantify the degree of weight loss required to confer benefit, correlate the impact of sustained weight loss on other AF risk factors, and evaluate the mechanism of reverse atrial remodelling in AF-naïve populations.’

Find this article online at JACC

References

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6. Kalman JM, Nalliah CJ, Sanders P. Surgical Weight Loss and Atrial Fibrillation: A Convenient Paradigm to Evaluate a Complex Problem. J Am Coll Cardiol 2016;68:2505-7.