A 36-year-old female nurse comes to the clinic due to a sensation of fast hea rate, slight dizziness, and vague chest fullness. Blood pressure is 110/70. The following rhythm strip is obtained, which shows

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.