Determinants of ECG misdiagnosis of atrial fibrillation or flutter in the emergency department and their clinical implications: results from a single-center observational study

Atrial fibrillation (AF) and atrial flutter (AFL) are common arrhythmias frequently misdiagnosed. The emergency department (ED), a fast-paced environment, presents challenges for accurate ECG interpretation. This study examined whether timing of ED presentation affects diagnostic accuracy. Over five years (2019–2024), consecutive ECGs from patients discharged with AF or AFL were independently reviewed by two cardiologists. Diagnoses were classified as correct, partially correct (AF misread as AFL or vice versa), or overinterpreted (non-AF/AFL rhythms misread as AF/AFL). Arrival times were grouped into morning (07:00–15:00), afternoon (15:00–23:00), and night (23:00–07:00) shifts. Multivariable logistic regression analyzed predictors of overinterpretation. Among 2,003 patients (1,794 AF; 209 AFL), interpretations were correct in 1,780 (88.9%), partially correct in 166 (8.3%), and overinterpreted in 57 (2.8%). Overinterpretation rates were highest in the afternoon (4.3%) versus morning (2.8%) and night (0.7%) (p = 0.012). Independent predictors included afternoon arrival (OR 1.87; 95% CI 1.07–3.25; p = 0.027) and premature beats (OR 2.22; 95% CI 1.30–3.81; p < 0.001). Overinterpretation was independent of shift workload and physician experience, and resulted in inappropriate new prescriptions of rate-control agents (38.5%), antiarrhythmics (28%), and anticoagulants (56%), with minor and major bleeding occurring in 16% and 3.5% of cases, respectively. Diagnosis was revised during outpatient follow-up in only 5% of cases. Overinterpretation of AF remains a concern in the ED. Error rates did not rise during nighttime shifts, implying that factors other than clinician fatigue may underlie these mistakes.