A 51-year-old woman comes to the office for a follow-up. The patient has hypertension treated with lisinopril, hydrochlorothiazide, and amlodipine. She also takes paroxetine for hot flashes ever since her menopause at age 50 and says she continues to experience occasional episodes of "hot flashes and anxiety." The patient has been monitoring her blood pressure at home and brings a report with highly variable blood pressure readings. She reports no weight changes, fatigue, chest pain, myalgias, or polyuria. She has been taking her medications as prescribed. The patient does not smoke cigarettes or drink alcohol. Her father died at age 65 from hemorrhagic stroke. Blood pressure is 170/100 in the right arm and 166/94 in the left arm, and pulse is 88/min. BMI is 24 kg/m². Physical examination is normal. Complete blood count, serum electrolytes, glucose, creatinine, and TSH level are within normal limits. What is the most appropriate next step in management?

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11ec25c8_d25b_a182_bc81_8751c955e8db_MD0003_00 This patient has resistant hypertension, which is defined as hypertension that persists despite treatment with antihypertensive agents from 3 different classes, one being a diuretic. Resistant hypertension should raise suspicion for a secondary cause. Although rare, pheochromocytoma is a potential cause of secondary hypertension that should be considered. Pheochromocytomas release an excess of catecholamines (ie, dopamine, epinephrine, norepinephrine) into the bloodstream, resulting in characteristic clinical manifestations. Paroxysmal hypertension (eg, highly variable blood pressure readings) is present in about half of patients and a clue to diagnosis in this patient. Her accompanying episodes of anxiety and "hot flashes" (eg, sweating) despite paroxetine therapy could also be manifestations of pheochromocytoma. The classic symptomatic triad, consisting of episodic headache, sweating, and tachycardia, is present in less than half of patients. The initial evaluation for pheochromocytoma involves the measurement of urine or plasma metanephrines, which are breakdown products of epinephrine and norepinephrine. Elevated metanephrine levels have high sensitivity for pheochromocytoma; therefore, normal levels usually rule out the disease. The specificity of elevated metanephrine levels is poor, however. Therefore, elevated levels warrant additional testing in the form of abdominal CT scan or MRI and/or positron emission tomography to confirm the presence and location of a pheochromocytoma. (Choice A) Many psychoactive agents, including tricyclic antidepressants and antipsychotics, can increase serum catecholamine levels and, when appropriate, should be tapered and discontinued prior to testing. However, selective serotonin reuptake inhibitors (eg, paroxetine) do not affect testing. (Choice B) Due to their addictive potential, benzodiazepines should generally be avoided in the treatment of anxiety. In addition, an underlying cause of this patient's intermittent anxiety should be ruled out. (Choice C) 24-hour urinary free cortisol is used to test for Cushing disease, which can cause secondary hypertension. However, the hypertension is typically constant rather than sporadic and is often accompanied by weight gain and characteristic physical features (ie, central obesity, purple abdominal striae). (Choice E) Renal duplex imaging allows for evaluation for renal artery stenosis (RAS), which is a potential cause of secondary hypertension. However, pheochromocytoma is a better explanation of this patient's labile blood pressure readings and episodes of anxiety and sweating. Labile blood pressure is not common with RAS. (Choice F) Obstructive sleep apnea is a common cause of secondary hypertension, but it is unlikely in this patient with normal BMI. Educational objective: Pheochromocytoma should be suspected in patients with resistant hypertension, especially in the presence of other suggestive features (eg, episodic anxiety, headaches, sweating, tachycardia). Measurement of urine or plasma metanephrine levels is the initial step in evaluation. References: Prevalence of clinically unsuspected pheochromocytoma. Review of a 50-year autopsy series. (http://www.ncbi.nlm.nih.gov/pubmed/6453259)

A 51-Year-Old Woman Comes to the Office for a Follow-Up