Definitions and outcomes reported in studies investigating the management of New Onset Atrial Fibrillation in acutely unwell patients admitted to the Intensive Care Unit: A Scoping Review

Abstract Background New-onset atrial fibrillation (NOAF) frequently occurs in critically ill patients admitted to intensive care units (ICUs), yet definitions and outcome reporting remain inconsistent across clinical studies. This heterogeneity impedes evidence synthesis and limits the development of standardized management strategies. Methods A scoping review was conducted following the Arksey and O’Malley framework and reported using PRISMA-ScR guidelines. Electronic databases were searched from 1990 to 2024 for randomized controlled trials and observational studies reporting on NOAF in acutely unwell ICU patients. Data on arrhythmia definitions and reported outcomes were extracted and categorized using the ISPOR framework. Results This is the first study to systematically examine and compare diagnostic criteria for NOAF in ICU-based research. Out of 8,477 records, 44 studies (4 RCTs, 12 prospective, and 28 retrospective observational studies) met inclusion criteria. Significant heterogeneity was found in how NOAF was defined, including arrhythmia duration thresholds, diagnostic criteria, and heart rate cutoffs. Outcomes were primarily clinician-reported (n=101), followed by observer-reported (n=74), biomarker (n=25), and patient-reported outcomes (n=4), with no performance outcomes identified. Common outcomes included rhythm and heart rate control, arrhythmia recurrence, mortality, and length of stay, though definitions and timeframes varied considerably across studies. Conclusions This review identifies substantial methodological variation in both the definition and measurement of NOAF in ICU research. The findings are immediately applicable to clinical practice, enabling ICU teams to benchmark diagnostic and monitoring approaches, align practice with guideline-based definitions, and identify patients who may benefit from structured post-discharge follow-up. They also provide evidence for the importance of the development a Core Outcome Set for NOAF.