This is an electrocardiogram from an 82 year old man with a history of lung disease and renal failure. At the time of this recording the patient was on Iron, Lasix, and bronchodilators. The EKG shows a regular rhythm at a rate of 141/min. This patient had been in atrial fibrillation in the past and the rhythm here is probably atrial flutter with 2:1 block although no flutter waves are seen. The QRS duration is widened at 105 ms and the tall R waves in V5 and S waves in V1 and V2 and the ST depression in the absence of digoxin suggest left ventricular hypertrophy. The QRS is too narrow for ventricular tachycardia and the brief R wave in V2 with the clean down-stroke of the V2 S wave argue against a ventricular origin. The patient was placed on digoxin with a slowing of the ventricular rate and a rhythm that was clearly atrial fibrillation and with a QRS with the same morphology.