Atrial fibrillation (AF) is a known complication of cardiac surgery, with incidence rates varying significantly across series and centers. The incidence is recognized to be higher following AVR compared to other interventions. Nonetheless, several questions remain concerning its prognostic implications in the medium and long term.

The primary objective of this work by Björn et al. is to provide evidence on the recurrence of atrial fibrillation during postoperative follow-up and complications associated with new-onset atrial fibrillation (NOAF) occurring during the same admission. A retrospective cohort of 1,073 patients undergoing AVR was analyzed, recruited across four hospitals in Finland. After excluding patients with a history of preoperative AF, 529 patients with biological prostheses and 253 with mechanical prostheses were included. The median follow-up was 5.4 years. During hospitalization, 333 patients (42.6%) experienced NOAF, and 250 (32%) had AF post-discharge. Among those with mechanical prostheses, 64 (25.4%) had NOAF during hospitalization, and 74 (29.2%) developed AF after discharge. Meanwhile, in the bioprosthetic cohort, 269 (50.9%) experienced NOAF during hospitalization, and 176 (33.3%) post-discharge. Patients with NOAF during hospitalization had an increased risk of AF during follow-up in the combined cohort (HR = 3.68; p < .001) as well as in both individual cohorts. Patients with mechanical prostheses (HR = 2.05; p = .025) and bioprostheses (HR = 1.63; p = .004) showed a higher risk of death during follow-up.

The study concludes that NOAF during hospitalization is associated with a 2- to 4-fold increase in risk of AF during follow-up and a 1.6- to 2-fold higher risk of all-cause mortality post-AVR.

COMMENTARY:

AVR remains one of the most performed cardiac surgeries in Western centers, with AF as one of the most frequent complications cardiac surgeons encounter during the immediate postoperative period. This study not only provides evidence of the incidence of this significant postoperative complication but also emphasizes its long-term prognostic role.

The authors themselves recognize limitations, including the retrospective nature of the study and the fact that AF diagnosis was based solely on electrocardiogram (ECG) readings during follow-up appointments and in symptomatic cases caused by the arrhythmia or other factors. This is notable as it’s possible that many asymptomatic paroxysmal AF episodes went undiagnosed post-discharge. Additionally, a more detailed collection of variables would have been beneficial. Knowing which intraoperative variables could predispose patients to NOAF could greatly impact the prevention of this complication. For instance, could the incidence of arrhythmic events vary based on the prosthesis type? It is well-known that AF rates are lower following TAVI compared to AVR, which raises the question of whether certain bioprosthetic options, such as sutureless prostheses, which involve less manipulation of the surgical field, were used and if their usage correlated with different AF incidence rates. Similarly, AVR can now be performed via various surgical approaches (traditional median sternotomy, mini-sternotomy, mini-thoracotomy). Determining whether surgical approach impacts the development of postoperative AF would be highly relevant, especially in patients with predisposing factors for arrhythmia.

The difference in all-cause mortality during follow-up between patients with NOAF in both groups deserves attention. The cohort treated with bioprostheses shows a higher mortality rate than those with mechanical prostheses. However, within the mechanical cohort, the mortality curves between patients with and without NOAF are more distinctly separated compared to the bioprosthetic cohort. This observation raises the question of whether new-onset AF is a complication that impacts medium- and long-term prognosis, influencing mortality, or if it merely reflects greater frailty and comorbidities in these patients, thus serving as a prognostic marker for identifying those at increased risk of mortality during follow-up.

The central takeaway from this study, with a large sample size and robust statistical analysis, is that NOAF following AVR predisposes patients to AF recurrence during follow-up and is associated with higher long-term mortality. Future studies should focus more on identifying perioperative variables that could decrease the incidence of postoperative AF, ultimately aiming to reduce medium- and long-term mortality following AVR.

REFERENCE:

Björn R, Nissinen M, Lehto J, Malmberg M, Yannopoulos F, Airaksinen KEJ, et al. Late incidence and recurrence of new-onset atrial fibrillation after isolated surgical aortic valve replacement. J Thorac Cardiovasc Surg. 2022 Dec;164(6):1833-1843.e4. doi: 10.1016/j.jtcvs.2021.03.101.