Q. A 47-year-old woman is brought to the emergency department due to a sudden loss of consciousness (syncope). Her daughter mentions that the syncope started while her mother was watching TV. It lasted 1 minute and was not associated with convulsion or urinary incontinence. The patient reports symptoms of chest palpitations and an ill-defined lightheadedness over the past one week. Her medical history is significant for osteoarthritis and premature ovarian failure. Her vital signs show BP: 84/52 mmHg, HR: 142 bpm, respiratory rate: 18/min, and temperature: 37.2 degrees Celsius. Upon examination, the patient is conscious however complains of chest palpitations. Her ECG is shown below. Which of the following is the primary cause of the patient's loss of consciousness?