(P199) THE LIPID PARADOX IN POSTOPERATIVE ATRIAL FIBRILLATION

Background: The combination of abdominal obesity and elevated triglycerides (TG), i.e. hypertriglyceridemic waist, is a known risk factor for coronary heart disease. Abdominal adiposity is also known to increase the risk of atrial fibrillation (AF). Yet, a lipid paradox has been described, where lower levels of low-density lipoproteins (LDL) and TG were associated with a higher risk of AF. We evaluated the role of the lipid profile on the incidence of postoperative atrial fibrillation (POAF) in patients undergoing coronary artery bypass grafting (CABG) and its interaction with abdominal obesity.

METHODS AND RESULTS: In a prospective registry of patients undergoing non-urgent on-pump isolated CABG (Quebec Heart Lung Institute, 2006-2019), we compared the lipid profiles of patients who did vs. did not develop POAF, defined as AF during hospitalization. We excluded patients with previous AF history, missing data, re-do procedures, perioperative mortality ( < 48h), permanent pacemakers or defibrillators. Non-parametric data were compared with Wilcoxon test. Our cohort included 7,785 individuals (19% female), among whom 2,387 developed POAF (31%). Baseline and perioperative characteristics are presented in Table 1. LDL and TG levels were lower in the POAF group (both p< 0.01). In a multivariable logistic regression model, adjusting for all characteristics in Table 1, statistically significant (p < 0.05) predictors of POAF were age, male sex, waist circumference, body-mass index, beta-blockers, preoperative hemoglobin, intensive care unit length of stay, cardiopulmonary bypass time, red blood cell transfusions, and TG levels (OR=0.88 [95%CI 0.82-0.94], p< 0.01). In the same model, when stratifying patients according to abdominal adiposity (waist circumference ≥90 cm [males], ≥85 cm [females]), the protective effect of elevated TG levels on POAF was statistically significant only in centrally obese patients (OR= 0.88 [95% CI 0.82-0.95], p< 0.01), while no association with TG was present in the subgroup without abdominal adiposity (p=0.86). When categorizing according to abdominal adiposity and below vs. above TG median, the subgroup “elevated WC + low TG” had a higher adjusted risk of POAF compared to the elevated TG subgroups. (Figure 1)

Conclusion: In this cohort, LDL levels were not associated with POAF, while lower TG levels were associated with a higher risk of POAF, especially in the subgroup of centrally obese patients. This is the first study to demonstrate a paradoxical association between low TG and POAF and to suggest the modifying role of abdominal adiposity in this association. Future mechanistic studies are needed to evaluate the role of TG in atrial cell metabolism.