A 82 year old male with a history of hypertension and coronary artery disease presents with generalized fatigue. His medications include metoprolol, amlodipine, aspirin and simvastatin. His temperature is 37.0, blood pressure 100/60, heart rate 50, respirations 20, and oxygen saturation 95% on room air. Physical examination is normal except for a slow heart rate. Laboratory studies are normal. His ECG is below (strip only). Which of the following is the most appropriate course of action?
A. Discontinue metoprolol
B. Administer atropine
C. Pacemaker implantation
D. Observation