POAF is the most frequent arrhythmia in patients undergoing cardiac surgery, with a prevalence exceeding 30%, especially in elderly patients, those undergoing valve procedures, and notably in combined procedures. Etiological factors contributing to its pathogenesis include atrial distention from perioperative volume overload, pericardial inflammation, hypoxia, tissue acidosis, and electrolyte imbalances.

In addition to its frequency, POAF is a complication with rising incidence linked to comorbidities such as COPD and diabetes mellitus, increasingly common in the patient population. While POAF might seem benign, it can result in various short-, medium-, and long-term postoperative complications, including heart failure and stroke. Due to the associated high morbidity and mortality, as well as healthcare costs, various management and prevention strategies have been implemented, although with variable results.
Bianco et al. conducted a single-center retrospective study including 12,227 patients who underwent cardiac surgery from 2011 to 2018, both elective and urgent cases. Exclusion criteria were a history of AF, surgical ablation procedures like Cox-Maze, heart transplant, or ventricular assist device implantation. Diagnosis relied on a 12-lead electrocardiogram and continuous telemetry monitoring in the early postoperative period, with follow-up every six months.

Patients were divided into two cohorts based on POAF presence, with an additional subanalysis according to surgery type (coronary revascularization, isolated valve, or combined procedures). Initial univariate analysis followed by logistic regression allowed for the calculation of a POAF propensity score based on preoperative characteristics, enhancing homogeneity and comparability between groups.
Baseline characteristics: Among the 12,227 patients, 7,927 showed no evidence of POAF, while the remaining 4,300 (35.2%) developed POAF. Additionally, 0.76% exhibited atrial flutter, and 2% had combined AF and flutter.
Postoperative outcomes: No significant differences in mortality, mediastinitis, or stroke were observed between groups. However, POAF patients showed significantly higher rates of reoperation, transfusions, sepsis, prolonged mechanical ventilation, and dialysis requirement (p < .001). The POAF group also had an increased need for intra-aortic balloon pump support (p = .003). Concerning surgery type, independent associations with POAF were found for aortic root replacement (p = .001), CABG combined with mitral valve surgery (p < .001), double mitral-aortic valve replacement (p< .001), and triple-valve surgery (p < .022). Female gender was associated with reduced POAF risk (p < .001).
A total of 1,538 patients (36.6%) were discharged with AF. Among these, only 27% were discharged on anticoagulation due to POAF occurrence. Warfarin was more frequently prescribed (66%) compared to Xa inhibitors (5%; p < .001), with 46.2% of patients discharged on amiodarone.
One- and five-year survival rates were higher in the non-POAF group (p < .001). Patients with POAF had a higher incidence of long-term AF (p < .001). There was no difference in ischemic or hemorrhagic stroke risk between groups (p= .385 and p = .946, respectively). POAF was associated with increased mortality risk (p < .001), especially among patients with preoperative COPD, dialysis requirement, and combined CABG with right-sided valve surgery. The POAF cohort showed a high readmission risk, particularly for COPD, diabetes, or prior heart failure decompensation, especially in patients undergoing triple valve surgery or discharged on oral anticoagulation, both at one and five years.
Bianco et al. concluded that multiple-valve replacements and combined procedures have the strongest association with POAF. However, associations were also present in coronary surgery and isolated valve replacement subgroups. POAF correlates with an elevated risk of mortality and hospital readmissions for multiple causes.

COMMENTARY:

Despite extensive research on POAF, this study stands out due to its large sample size and extended follow-up. The findings support associations identified by other researchers regarding POAF and high-risk patient characteristics, such as procedure types, risk factors, and postoperative complications. Novel findings include the association of POAF with increased short- and long-term mortality, underscoring POAF as an independent factor linked to reduced survival. The readmission findings highlight POAF’s impact not only in the short-term (30 days) but also at one and five years, including a high risk of readmission due to heart failure.

The results raise a question: Is POAF an etiological factor leading to patient deterioration, resulting in reduced survival, or is it simply a marker of higher disease burden and frailty in patients already predisposed to shorter life expectancy? Addressing this requires considering specific AF types and patient monitoring. Not all AFs are the same; those occurring in patients with perioperative complications like sepsis or inotropic/mechanical support needs differ from transient AF without associated complications. Furthermore, patients with complex postoperative courses might have been monitored more closely, potentially leading to a selection bias that may explain the poorer outcomes in the POAF group.

While it is known that POAF typically occurs within the first 72 hours, Bianco et al.’s work provides a longer perspective, not limited to the early postoperative period. This raises questions about AF types and their impact on survival, readmission, and complications. Despite its value, there remain knowledge gaps in cardiac surgery regarding POAF that future studies with varied parameters could help fill, aiming to improve understanding and prevention.

REFERENCE:

Bianco V, Kilic A, Yousef S, Serna-Gallegos D, Aranda-Michel E, Wang Y, et al. The long-term impact of postoperative atrial fibrillation after cardiac surgery. J Thorac Cardiovasc Surg. 2023 Oct;166(4):1073-1083.e10. doi: 10.1016/j.jtcvs.2021.10.072.