A 29 year old female with a history of hypertension presents for a routine clinic visit without any physical complaints. Her blood pressure is 180/100 which she admits it has been at home as well. Physical examination reveals normal lung sounds, a regular rhythm with a hyperdynamic apical impulse and an S4 heart sound, an abdominal bruit is heard, no lower extremity edema. Her pulses are 2+ in upper and lower extremities. Her blood pressure medications include lisinopril, amlodipine, atenolol, hydrochlorothiazide, hydralazine, and clonidine which she states she takes regularly. Screening for secondary causes of hypertension thus far has been negative which has included electrolytes, a complete blood count, creatinine, urinary and serum catecholamines, AM cortisol levels, renin/aldosterone levels, thyroid stimulating hormone levels, and a dexamethasone suppression test. Which of the following tests should be ordered next?