The Incidence and Natural Progression of New-Onset Postoperative Atrial Fibrillation.

Objectives: This study aimed to characterize the natural progression and recurrence of new-onset postoperative atrial fibrillation (POAF) during an intermediate-term follow-up post cardiac surgery by using continuous event monitoring.

Background: New-onset POAF is a common complication after cardiac surgery and is associated with an increased risk for stroke and all-cause mortality. Long-term data on new POAF recurrence and anticoagulation remain sparse.

Methods: This is a single-center, prospective observational study evaluating 42 patients undergoing cardiac surgery and diagnosed during indexed admission with new-onset, transient, POAF between May 2015 and December 2019. Before discharge, all patients received implantable loop recorders for continuous monitoring. Study outcomes were the presence and timing of atrial fibrillation (AF) recurrence (first, second, and more than 2 AF recurrences), all-cause mortality, and cerebrovascular accidents. A "per-month interval" analysis of proportion of patients with any AF recurrence was assessed and reported per period of follow-up time. Kaplan-Meier analysis was used to calculate the time to first AF recurrence and report the first AF recurrence rates.

Results: Forty-two patients (mean age 67.6 ± 9.6 years, 74% male, mean CHADSVASc 3.5 ± 1.5) were evaluated during a mean follow-up of 1.7 ± 1.2 years. AF recurrence after discharge occurred in 30 patients (71%) and of those, 59% had AF episodes equal to or longer than 5 minutes (median AF duration at 1 month was 32 minutes [interquartile range 5.5-106], whereas median AF duration beyond 1 month was 15 minutes [interquartile range 6.3-49]). Twenty-four (80%) of the 30 patients had their first AF recurrence within the first month. During months 1 to 12 follow-up, 76% of patients had any AF recurrences (10% had their first AF recurrence, 43% had their second AF recurrence, and 23% had more than 2 AF recurrences). Beyond 1 year of follow-up, 30% of patients had any AF recurrences (10% had their first AF recurrence, 7% had their second AF recurrence, and 13% had more than 2 AF recurrences). Using Kaplan-Meier analysis, the median time to first AF recurrence was 0.83 months (95% CI: 0.37 to 6) and the detection of first AF recurrence rate at 1, 3, 6, 12, 18, and 24 months was 57.1%, 59.5%, 64.3%, 64.3%, 67.3%, and 73.2%, respectively. During follow-up, there was 1 death ([-] AF recurrence) and 2 cerebrovascular accidents ([+] AF recurrence).

Conclusions: In this study of continuous monitoring with implantable loop recorders, the recurrence of AF in patients who develop transient POAF is common in the first month postoperatively. Of the patients who developed postoperative AF, 76% had any recurrence in months 1 to 12, and 30% had any recurrence beyond 1-year follow-up. Current guidelines recommend anticoagulation for POAF for 30 days. The results of this study warrant further investigation into continued monitoring and longer-term anticoagulation in this population within the context of our findings that AF duration was <30 minutes beyond 1 month.