A 40-Year-Old Man Is Brought to the Emergency Department Due

question 56

Multiple Choice

A 40-year-old man is brought to the emergency department due to sudden onset palpitation and chest discomfort. He has no prior medical conditions and takes no mediations. Chest examination reveals no murmurs and the lungs are clear on auscultation. ECG reveals a heart rate of 126/min with an irregularly irregular rhythm, narrow QRS complexes, and no organized P waves.  Which of the following physiologic factors most likely determines the ventricular contraction rate in this patient?

• A)Atrial muscle depolarization rate
• B)Atrioventricular node refractory period
• C)Bundle branch conductivity
• D)Purkinje system pacemaker activity
• E)Sinoatrial node discharge rate
• F)Ventricular muscle refractory period

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