A 69-year-old woman presents with palpitations and dyspnoea. ECG shows new-onset atrial fibrillation with a ventricular rate of 130 beats/min. She is haemodynamically stable. Her comorbidities include hypertension and heart failure with preserved ejection fraction; she has no history of stroke or TIA. According to the CCS atrial fibrillation guideline using the CHADS-65 approach, what is the best strategy for stroke prevention?