A 76-year-old man sought follow-up care after his primary care provider retired. The patient considered himself to be healthy, performed activities of daily living independently, had had no falls, and walked 1 to 3 miles daily without difficulty. He had a 5-year history of well-controlled type 2 diabetes mellitus, which was being treated with a single oral agent, and a 10-year history of hypertension, which was being treated with a low-dose diuretic and an angiotensin-converting enzyme inhibitor. The patient had been told that he had had an irregular pulse rate for 1 to 2 years, but he was unaware of any symptoms. A review of systems was otherwise normal.

On examination, the patient's body mass index was 27 kg/m², his blood pressure was 130/70 mm Hg, and his pulse was 90 beats/minute and irregularly irregular. The remainder of the examination, including the cardiovascular exam, was normal. The complete blood count and multiphasic lab panels were normal, and the patient's glycosylated hemoglobin was 7.5%. An electrocardiogram showed atrial fibrillation at a rate of 90 to 96 beats/minute. A review of old records showed that atrial fibrillation was present on an electrocardiogram performed 1 year earlier. In addition to a rate control agent, should this patient be treated with warfarin?