A pilot, single-center, prospective, interventional study. The objective is to demonstrate that catheter-based renal denervation using carbon dioxide renal angiography in patients with moderate to severe chronic kidney disease can be performed for treatment of uncontrolled hypertension.

Renal sympathetic denervation has been shown to be safe and effective in patients with uncontrolled hypertension and estimated Glomerular Filtration Rate (eGFR)>45 mL/min per 1•73 m². However, the safety and efficacy of this has not been studied in patients with more severe renal impairment. The investigators aim to examine safety and efficacy of renal denervation (RDN) in patients with eGFR between 44 and 15 ml/min/1.73 m2 (CKD 3b & 4) in a pilot study which may be a precursor of a large observational study in the future. Moreover, the current imaging protocol and procedure protocol for renal sympathetic denervation requires the use of iodinated contrast, which can have deleterious effects on renal function. The investigators have a proven track record for the use of carbon dioxide angiography in renal artery intervention. The investigators would like to use carbon dioxide angiography in this study to minimize contrast induced deterioration in renal function in this cohort which may again be a precursor of a farther larger study.

Inclusion Criteria:

• Patients aged 18-75 years with a clinic systolic blood pressure of 140 mm Hg or more despite compliance with three or more antihypertensive drugs,
• eGFR<45 and >15 mL/min per 1.73 m².

Exclusion Criteria:

• eGFR <15 mL/min per 1.73 m²,
• Type 1 diabetes,
• Substantial stenotic valvular heart disease,
• Pregnancy or planned pregnancy during the study,
• A history of myocardial infarction, unstable angina, or cerebrovascular accident in the previous 6 months.