Review Question - QID 214567

A 67-year-old man presents to his primary care physician with shortness of breath when he exerts himself. It has been gradually worsening over the past month, requiring the patient to avoid activities he previously enjoyed such as going for walks. Today, while walking, the patient felt short of breath and then fainted. He woke up roughly 10 seconds later and was at his baseline. His temperature is 98.0°F (36.7°C), blood pressure is 154/118 mmHg, pulse is 89/min, respirations are 18/min, and oxygen saturation is 98% on room air. Physical exam reveals bilateral clear breath sounds, a soft systolic murmur, and an absence of lower extremity edema. An ECG is performed as seen in Figure A. Which of the following is most likely present in this patient?