Review Question - QID 108149

A 24-year-old man visits his primary care doctor complaining of increasing shortness of breath, lightheadedness, and weight gain. He has no medical problems. He works as a landscaper but has recently been unable to keep up with his duties due to fatigue. He recalls having a large rash on his arm 6 weeks ago but did not seek medical care at that time (Figure A). On physical exam, temperature is 37.1 deg C (98.8 deg F), pulse 40/min and weak, blood pressure is 110/68 mmHg, and respiratory rate is 20/min. He is pale and there is swelling of the lower extremities is noted. A 12-lead EKG is shown (Figure B). What is the most likely cause of the patient’s symptoms?