A 71-year-old man comes to the physician for a health maintenance examination. He reports occasional lightheadedness but otherwise has no past medical history. He walks the dog 4 days per week for 30 minutes at a time. Blood pressure is 130/80. Fasting blood glucose is 90 mg/dL. Lungs are clear to auscultation. In addition to metoprolol, which of the following is the most appropriate initial pharmacologic therapy?
Aspirin
Clopidogrel
Flecainide
Heparin
Warfarin
