A 70-year-old man with newly diagnosed non-valvular atrial fibrillation is seen in clinic. He has hypertension but no diabetes, heart failure, prior stroke, or vascular disease. He is otherwise well and has normal renal function. According to the Canadian Cardiovascular Society atrial fibrillation guideline using the CHADS-65 algorithm, which is the most appropriate antithrombotic strategy for stroke prevention?