This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
[{'content': 'A 68-year-old man presents with a syndrome of alcohol withdrawal. ECG Shows? \nSelect and explain. \nA. Atrial flutter, B. Atrial fibrillation, C. PSVT, D. VT', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Atrial flutter.* This ECG reveals a regular narrow complex tachycardia at a rate of 150 beats/min. Coarse sawtooth waves are seen best in the inferior leads diagnostic of atrial flutter with 2 to 1 AV conduction.* Whenever a supraventricular tachycardia at a rate of close to 150 beats/ min is present, the diagnosis of atrial flutter should be considered. The QRS axis is normal, and there is no clear evidence of ischemia.* Typical atrial flutter is caused by a macro-reentrant circuit in the right atrium, involving the tricuspid annulus. Structural heart disease, intrinsic lung disease, and states of increased sympathetic tone can all predispose to this arrhythmia.', 'role': 'assistant'}]