Inclusion criteria:

Subjects with resistant hypertension as defined by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) guidelines, systolic blood pressure and/or diastolic blood pressure > 140/90 mm Hg. For patients with hypertension and diabetes or renal disease, blood pressure > 130/80 mm Hg despite treatment with diuretic, sympathetic depressant and vasodilators.

Medications may include a three drug regimen including:

• diuretic at therapeutic dose
• a second line agent such as sympatholytic (e.g. beta-blockade, central agent such as clonidine) or angiotensin converting enzyme inhibitor (ACEi) / angiotensin receptor blocker (ARB) or calcium channel blocker (CCB).
• third line agent including one of the above and/or direct vasodilator, such as hydralazine or minoxidil.

Exclusion criteria:

• Congestive Heart Failure (any NYHA class)
• Ejection Fraction < 50%
• Known renal artery stenosis
• Myocardial infarction within 3 months of screening
• Unstable angina within 14 days of screening, or any evidence of myocardial ischemia
• Moderate to severe pulmonary hypertension
• Valvular stenosis, hypertrophic, restrictive or obstructive cardiomyopathy, constrictive pericarditis, primary pulmonary hypertension, or biopsy proven active myocarditis
• Sustained ventricular tachycardia or ventricular fibrillation within 14 days of screening
• Sustained Atrial Fibrillation
• Second or third degree AV block without a permanent cardiac pacemaker
• Cerebral vascular accident within 3 months of screening, or other evidence of significantly compromised central nervous system perfusion
• Total bilirubin of > 1.5 mg/dL or aspartate aminotransferase (AST) and alanine aminotransferase (ALT) 1.5 times the upper limit of normal range
• Renal insufficiency assessed by calculated GFR < 30 ml/min (Cockroft-Gault equation)
• Serum sodium of < 125 mEq/dL or > 160 mEq/dL
• Serum potassium of < 3.0 mEq/dL or > 5.5 mEq/dL
• Women taking hormonal contraceptives
• Pregnancy
• Body mass index (BMI) > 35