Association between acute kidney injury and atrial fibrillation in patients undergoing cardiac surgery

Introduction Atrial fibrillation (AF) is the most common arrhythmia following cardiac surgery, affecting up to 50% of patients in the immediate postoperative period. Postoperative AF is associated with increased morbidity, mortality and prolonged ITU stay. Recent guidelines (1) have identified age >75, history of AF, renal failure, mitral valve surgery/pathology, heart failure and chronic obstructive pulmonary disease as preoperative risk factors for developing new postoperative AF, with the intention of providing these patients with pre-emptive treatment to reduce the risk of AF in the postoperative period. We hypothesised that acute kidney injury (AKI) in the postoperative period could be an additional risk factor for the development of AF. Methods We performed an analysis on routinely collected data from patients who underwent elective cardiac surgery at our institution between 1st July 2013 and 31st December 2018. Patients who had pre-existing cardiac arrhythmias and patients who had undergone previous cardiac surgery were excluded. Multivariable logistic regression was used to explore the associations that postoperative AKI (defined as an increase in baseline creatinine by a minimum of 26.4 µmol/L or by 50% of the baseline measurement, during the first 48 hours after surgery) and preoperative risk factors had with postoperative AF. Results A total of 5588 patients were included in the study. The incidence of postoperative AF was 1384 (24.8%), postoperative AKI occurred in 686 patients (12.3%). Postoperative AKI was significantly associated with postoperative AF after adjustment for preoperative variables (adjusted odds ratio = 1.572; confidence interval = 1.295 to 1.908; p = III, previous congestive heart failure, recent MI, routine use of hypertension medication, CABG + valve surgery and aortic surgery (see Table 1). Discussion This analysis of a large, contemporary cohort of patients identifies postoperative AKI as an associated risk factor for postoperative AF, along with other preoperative variables. Early identification of this patient cohort would allow targeted preventative treatment to reduce the incidence of postoperative AF. This analysis provides impetus for clinical trials that further explore the association between AF and AKI.