Multifocal atrial tachycardia (MAT), characterized by an irregularly irregular rhythm, is often regarded as a clinical imitator of atrial fibrillation (AF). We aimed to evaluate the prevalence of MAT misclassification as AF in the emergency department (ED) setting.

A retrospective analysis of 1828 ECGs from patients discharged with AF diagnoses over five years. All tracings were independently reviewed by three blinded cardiologists.

MAT was identified in one case (0.05 %). Other misclassifications included atrial flutter (7.9 %), supraventricular tachyarrhythmias (1.6 %), and sinus rhythm with conduction disturbances, artifacts, or ectopy (1.0 %).

Misdiagnosis of MAT as AF in the ED is rare. However, other diagnostic errors remain relatively common, underscoring the need for careful rhythm evaluation.