This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Electrocardiography, Subject name: Medicine
[{'content': 'A 50-year-old patient complains of dizziness and palpitations. ECG shows? \nSelect and explain. \nA. Bradycardia-tachycardia syndrome, B. Mobitz I block, C. Mobitz II block, D. Complete heart block', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Bradycardia-tachycardia syndrome.ECG shows runs of tachycardia interspersed with long sinus pauses.The sinus rate is slow to level that it looks like an arrest.Sinus beats are followed by paroxysms of junctional tachycardia at 140 bpmNone of the definitions of Mobitz I and II blocks discussed above are satisfied.', 'role': 'assistant'}]