Trends in newly diagnosed atrial fibrillation and oral anticoagulant use after cardiac surgery: a population-based analysis from Ontario, Canada
Authors: Lee J G , Ha A C T , Jeong I , Fang J , Ouzounian M , Austin P C 
Published: November 2023

Abstract

Background
Post-operative atrial fibrillation after cardiac surgery is associated with an increased risk of death and ischemic cardiovascular outcomes. In the non-surgical setting, oral anticoagulation (OAC) is beneficial among patients with AF in reducing their risk of thromboembolism. The use of OAC for patients with post-operative AF after cardiac surgery is not well-defined in contemporary clinical practice - at a time when direct oral anticoagulants (DOAC) are commonly prescribed in the non-surgical setting.

Purpose
To examine trends in OAC use among patients with post-operative atrial fibrillation after cardiac surgery at a time when DOAC is commonly prescribed in clinical practice.

Methods
The study cohort consisted of consecutive patients (&gt;65 years) who experienced post-operative AF within 90 days after coronary artery bypass grafting (CABG), isolated left-sided non-mechanical heart valve surgery (iValve), and combined CABG + valve surgery between 2008 and 2021, identified by a mandatory provincial registry of all patients undergoing cardiac surgery in Ontario, Canada. Key exclusion criteria included: patients with pre-existing AF, end-stage renal disease requiring dialysis, mechanical heart valves, left atrial appendage ligation, and those who required anticoagulation for non-AF indications. Prescription of OAC (warfarin or DOAC) within 90 days after discharge from surgery was collected via linkage with the Ontario Drug Benefits Plan.

Results
The overall cohort consisted of 45,571 patients, in whom 14,572 (32.0%) developed POAF after cardiac surgery. Rates of POAF were highest among patients who underwent combined CABG + valve surgery (44.3% in 2008 to 34.2% in 2021), followed by iValve (42.6% in 2008 to 37.3% in 2021), then followed by isolated CABG (27.6% in 2008 to 24.2% in 2021). Over the study period, there was a decrease in the rates of POAF among patients who underwent all three types of cardiac surgery (P[trend] &lt;0.01). In 2021, rates of oral anticoagulation were highest among patients who underwent combined CABG + valve surgery (61.1%), followed by iValve (59.2%) and isolated CABG (42.0%). Among patients who underwent isolated CABG, there was a 9% increase in the rates of OAC use during the study period (P[trend] &lt;0.001). On the other hand, rates of OAC use remained largely unchanged (Figure A) among patients who underwent iValve and combined CABG + valve surgery (P[trend] 0.24 and 0.26, respectively). Since 2018, DOAC accounted for 60-70% of all OAC prescriptions (Figure B).

Conclusions
Despite advances in surgical techniques and post-operative care, the rates of post-operative atrial fibrillation after cardiac surgery remain substantial. Prescription rates for OAC remain modest over the past decade, but DOAC is increasingly more commonly prescribed in this patient population. Randomized trials are needed to assess the risks and benefits of OAC, specifically DOAC, in this high-risk patient population.Figure AFigure B