Review Question - QID 214612

An 84-year-old man with a history of diabetes, hypertension, and hypercholesterolemia is brought to the emergency department after falling at his grandson's outdoor soccer game. He recalls waking up shortly after falling and was alert and oriented according to his wife. She says that he fell suddenly without warning, and she did not observe seizures, tongue biting, or incontinence. In the past, he occasionally gets dizzy upon standing up and has had 2 episodes of syncope. He is currently taking lisinopril and atorvastatin. His temperature is 99.1°F (37.3°C), blood pressure is 105/60 mmHg, pulse is 58/min, and respirations are 14/min. An EKG is performed with the results shown in Figure A. A CT head without contrast shows no ischemia. Which of the following is the most likely cause of syncope in this patient?