Incidental Detection of Cardiac Arrhythmias during Routine Electroencephalography: Prevalence and Clinical Significance of Single-lead ECG Monitoring

Aim: Routine electroencephalography (EEG) recordings often include a single-lead electrocardiogram (ECG) channel, primarily to identify cardiac artifacts. However, incidental detection of cardiac arrhythmias during EEG may provide clinically relevant information. This study aimed to assess the prevalence and clinical relevance of arrhythmias detected during routine EEG. Methods: This retrospective, descriptive, observational study included outpatient EEG recordings that were performed between April 2023 and December 2024. Routine and sleep EEGs recorded with simultaneous single-lead ECGs were analyzed. Reports were screened using arrhythmia-related keywords. Clinical, electrophysiological, and follow-up data were reviewed, and patients were compared by age group (<50 and ≥50 years). Results: Arrhythmia-related findings were identified in 157 EEG reports (3.6%). Extrasystoles were the most frequent arrhythmia (35%), followed by atrial fibrillation (AF) (21%). Atrial fibrillation was observed exclusively in patients aged ≥50 years and showed a significant positive correlation with age (r=0.413, p<0.001). In six patients (3.8%), arrhythmias detected on EEG led to referral to cardiology and subsequent diagnosis of clinically significant cardiac conditions. Conclusion: Single-lead ECG monitoring during routine EEG can reveal clinically important arrhythmias, including previously undiagnosed AF. Careful interpretation of ECG traces recorded during EEG may facilitate timely cardiology referral and improve patient management.