A 64-year-old woman comes to the physician two hours after a 5-minute painless loss of vision in her right eye. She reports no other symptoms. She has hypertension managed with lisinopril. Blood pressure is 150/90. A grade 3/6 holosystolic murmur is auscultated at the apex. Neurologic examination shows no abnormalities. Which of the following is the most appropriate next best step in diagnosis?
Ambulatory ECG monitoring
Duplex ultrasonography
Echocardiography
Electrocardiography
Non-contrast CT of the head
