A 44-year-old Caucasian woman presents to the emergency room complaining of breathlessness and heart palpitations. Her past medical history is significant for breast cancer treated with several...

A 44-year-old Caucasian woman presents to the emergency room complaining of breathlessness and heart palpitations. Her past medical history is significant for breast cancer treated with several chemotherapies including Adriamycin. Her ECG strip reveals an elevated (350 bpm) heart rate; it is regular with more P waves than QRS complexes; and her QRS complexes are normal. What arrhythmia do you suspect?

A. Ventricular fibrillation

B. Ventricular tachycardia

C. Atrial fibrillation

D. Atrial flutter