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 36-year-old white female nurse comes to the ER due to a sensation of fast heart rate, slight dizziness, and vague chest fullness. Blood pressure is 110/70. The following rhythm strip is obtained, which shows? \nSelect and explain. \nA. Atrial fibrillation, B. Atrial flutter, C. Supraventricular tachycardia, D. Ventricular tachycardia', 'role': 'user'}, {'content': 'Answer: C \nExplanation: (c) Source: (Fuster, 10/e, pp 809-812, 820-825, 837-841.) Paroxysmal supraventricular tachycardia due to AV nodal reentry typically displays a narrow QRS complex without clearly discernable P waves, with a rate in the 160 to 190 range. The atrial rate is faster in atrial flutter, typically with a classic sawtooth pattern of P waves, with AV conduction ratios most commonly 2:1 or 4:1, leading to ventricular rates of 150 or 75/min. Atrial fibrillation would show an irregularly irregular rhythm. Wide QRS complexes would be expected in ventricular tachycardia.', 'role': 'assistant'}]