A 48-year-old male with a history of hypertension refractory…

A 48-yeаr-оld mаle with а histоry оf hypertension refractory to multiple antihypertensive medications presents to the ED with sudden-onset episodic headaches, palpitations, and diaphoresis. His blood pressure is 210/115 mmHg, and his heart rate is 120 bpm. On exam, he appears anxious but has no focal neurological deficits.Which of the following is the most appropriate initial diagnostic test?