Comment: This ECG was incorrectly interpreted as atrial fibrillation while the patient was in the ER, likely because of the irregular rhythm. Note that in lead II, the 5th, 6th, and and 14th beats are associated with a negative P-wave in the inferior leads – these are likely an ectopic atrial rhythm and not necessarily “premature” as the rate is similar to the sinus rate. The 3-4 consecutive premature atrial complexes at the beginning and later part of the ECG can also be called non-sustained atrial tachycardia.