(P141) SEX DIFFERENCES IN POST-OPERATIVE ATRIAL FIBRILLATION AFTER CARDIAC SURGERY: A RETROSPECTIVE SINGLE-CENTRE COHORT STUDY

Background: Post-operative atrial fibrillation (AF) is the most common complication following cardiac surgery, occurring in up to 30% of cases. Post-operative AF is defined as new-onset AF occurring within the first 30 days following surgery. There is uncertainty whether post-operative AF is a reversible phenomenon or requires oral anticoagulation therapy to reduce long-term risk for stroke and mortality. Female sex is recognized as a risk-modifier in non-operative AF, but the role of biological sex in post-operative AF is unclear. This study explores sex differences in the rate of AF recurrence following cardiac surgery, in patients with new-onset post-operative AF.

METHODS AND RESULTS: This retrospective observational study includes all patients seen at the Cardiac Surgery Post-Operative Atrial Fibrillation Follow-up Clinic at the Hamilton General Hospital between 2020-2024. Every patient with new-onset post-operative AF during admission for cardiac surgery is referred to the clinic. Patients wear a 14-day Holter monitor 2-3 months following surgery and are seen in the clinic thereafter. The primary outcome of this study was AF lasting at least 30 seconds, captured on the follow-up Holter monitor. We compared recurrence rates for males and females using a multivariable logistic regression model adjusted for age, CHA2DS2-VASc score [excluding age and sex], surgery type, and left atrial size.

The cohort consisted of 714 patients, with a mean age of 68+/-9 years, a median CHA2DS2-VASc score of 3 (interquartile range [IQR] 2-3), and 22% were female. Of these patients, 52% (n=374) had an isolated coronary artery bypass grafting surgery, 89% (n=636) were receiving amiodarone at hospital discharge and 47% (n=334) were receiving oral anticoagulation. The mean time to follow-up Holter monitor was 75 days (IQR 72-88). Recurrent AF was detected on follow-up Holter in 9.5% (n=68) of patients. Among patients with recurrent AF, the median AF duration was 9 hours (IQR 1.4-188.7), and 28% (n=19) had persistent AF throughout the duration of their Holter. Oral anticoagulation was continued in 11% (n=81) of patients, initiated in 2% (n=14), and discontinued in 35% (n=253).

The crude rate of AF recurrence was higher in females as compared to males (12.4% versus 9.6%); however, we found no significant association between female sex and AF recurrence (adjusted relative risk 1.3 [95%CI 0.5-2.8] (Table 1).

Conclusion: Among patients who have post-operative AF during hospitalization for cardiac surgery, approximately 10% will have AF recurrence when followed systematically with Holter monitors. Females may have nominally higher rates of AF recurrence.