Postoperative atrial fibrillation following cardiac surgery in severe obesity: the added value of waist circumference.

Introduction: Obesity is an independent risk factor for postoperative atrial fibrillation (POAF) after coronary artery bypass grafting (CABG) surgery. POAF in patients with severe obesity (body mass index [BMI] ≥ 35 kg/m²) is less studied. Whether waist circumference (WC) improves prediction of POAF independently of BMI among patients with severe obesity remains unknown.

Aim: To evaluate the risk of POAF, the role of WC in predicting POAF and postoperative complications after CABG surgery in severe obesity.

Methods: Our cohort included 7995 patients undergoing CABG surgery (2006-19). POAF risk was compared across BMI and WC categories. In patients with severe obesity, the association of an increase in WC with POAF risk was assessed.

Results: 763 (9.5%) patients had a BMI ≥ 35 kg/m². In this group, BMI was 38.5 ± 3.6 kg/m² and WC was 123.4 ± 10.8 cm. More patients with severe obesity developed POAF compared to patients with a normal BMI (37 vs. 29%, aRR: 1.52[95%CI 1.36-1.72], p < 0.01). Within each BMI category, the risk of POAF was higher per increasing tertile of WC (p < 0.05). Among patients with a BMI ≥ 35 kg/m², every 10 cm increment in WC was associated with an increased risk of POAF (aRR: 1.16[95%CI 1.08-1.24], p < 0.01). POAF in patients with severe obesity was associated with increased hospital length of stay.

Conclusions: Severe obesity increases the risk of POAF after CABG surgery. In this subgroup, elevated WC may provide additional prognostic value independently of BMI. Since POAF is associated with adverse long-term outcomes, abdominal obesity by measurement of WC should be assessed and targeted even in patient with severe obesity. Central Illustration Increasing waist circumference associated with increased atrial fibrillation risk post coronary artery bypass grafting. Bar graph of the unadjusted absolute risk and 95% confidence interval of postoperative atrial fibrillation for each tertile of waist circumference per body mass index category. Comparison of postoperative atrial fibrillation risk with chi-square test showing an increasing risk of postoperative atrial fibrillation related to increasing waist circumference within each body mass index category.

Abbreviations: BMI, body mass index; POAF, postoperative atrial fibrillation; WC, waist circumference.