Review Question - QID 107968

A 43-year-old woman presents to the emergency department with complaints of acute onset shortness of breath. On physical exam, the patient has a loud holosystolic murmur heard best at the apex with radiation to the left axilla. Bilateral breath sounds are heard, slightly diminished, with pronounced bilateral crackles. While in the examination room, the nurse calls to inform you that the patient’s heart rate is 182/min and blood pressure is 72/45 mmHg. The patient appears drowsy and is not answering questions appropriately. The cardiac monitor demonstrates the following rhythm (Figure A). Which of the following is the most likely explanation for this patient’s sudden hypotension?