New-Onset Atrial Fibrillation in Critically Ill Patients: A Systematic Review of In-Hospital and Post-Discharge Outcomes

OBJECTIVES: This systematic review and meta-analysis determines the incidence of new-onset atrial fibrillation (NOAF) in critically ill patients, risks of post-discharge systemic thromboembolism, anticoagulation therapy, and the proportion diagnosed with AF post-discharge. DATA SOURCES: A search of registered databases (PubMed, Embase, Scopus, and CINAHL) was performed from inception to April 20, 2026. STUDY SELECTION: Eligible studies included critically ill patients (≥ 18 yr old) who developed NOAF during admission to general ICUs or high-dependency units. NOAF was defined as AF in patients without prior history of AF. DATA EXTRACTION: Data were independently extracted from full-text versions of included studies by nonblinded reviewers. DATA SYNTHESIS: A Bayesian meta-analysis was conducted on 54 studies (367,896 patients) with a random-effects model using R (Version 4.3.3). Pooled incidence of NOAF in critically ill patients was 10.6% (95% credible interval [CrI], 8.6-12.9%). Absolute risk of post-discharge systemic thromboembolism was 7.1% (95% CrI, 4.5-11.0%), changing to 6.9% (95% CrI, 4.2-11.6%) after age and sex adjustment. Evidence from six studies reports that critically ill patients with NOAF had 1.94 times (95% CrI, 1.23-3.29) higher relative risk of systemic thromboembolism post-discharge than patients without NOAF, rising to 2.01 (95% CrI, 1.54-2.80) with adjustment. Absolute and relative risk are evaluated with follow-up durations ranging from 1.5 months to 5 years, with variable anticoagulation exposure. Anticoagulation rates were low: 32.9% in-hospital (95% CrI, 14.6-57.9%) and 35.9% post-discharge (95% CrI, 19.7-55.9%). On follow-up, 23.9% (95% CrI, 13.9-38.5%) of critically ill patients with NOAF were subsequently diagnosed with AF. CONCLUSIONS: Our review suggests that NOAF during critical illness is associated with significantly increased risk of post-discharge systemic thromboembolism and subsequent AF diagnosis. However, rates of anticoagulation initiation remain low, highlighting the need for improved risk stratification and targeted strategies post-discharge.