Renal denervation (RDN) is a minimally invasive, catheter-based procedure developed as a treatment for high blood pressure, particularly for patients whose condition is difficult to manage with medication alone. This technique targets and disrupts specific nerves surrounding the renal arteries to reduce the overactivity of the sympathetic nervous system. The primary use of RDN is for individuals suffering from resistant hypertension, a condition where blood pressure remains elevated despite the use of multiple antihypertensive drugs.
The Target: The Sympathetic Nervous System and Blood Pressure
The rationale behind RDN lies in the relationship between the kidneys and the sympathetic nervous system, which acts as the body’s “fight or flight” response system. The kidneys are extensively innervated by a dense network of renal nerves, which include both efferent and afferent fibers.
Efferent nerves carry signals from the brain and spinal cord to the kidneys, regulating functions like the release of renin and the retention of sodium and water. When the sympathetic nervous system becomes overactive, as is common in chronic hypertension, these efferent signals cause the kidneys to retain more salt and water, and to release an excess of renin.
Renin is a hormone that initiates a cascade leading to vasoconstriction, or the narrowing of blood vessels, which collectively raises blood pressure. Afferent nerves carry signals from the kidneys to the central nervous system, further contributing to the overall heightened sympathetic tone throughout the body.
Disrupting these renal nerves effectively breaks this feedback loop of sympathetic overactivity that contributes to persistent high blood pressure. By reducing the outflow of efferent signals, the procedure helps decrease the release of blood-pressure-raising hormones and promotes the excretion of sodium. Interrupting the afferent signals also helps to lower the overall sympathetic activity in the central nervous system.
The RDN Procedure: Minimally Invasive Technique
The renal denervation procedure is performed using a specialized catheter inserted through a small puncture, typically in the femoral artery in the groin. The physician guides the catheter using X-ray imaging until it reaches the renal arteries, which supply blood to the kidneys. Patients are often under light sedation or local anesthesia during the process.
Once positioned within the renal artery, the specialized catheter delivers energy to the artery wall to disrupt the sympathetic nerves that run along the outside of the vessel. The two primary energy sources used are radiofrequency (RF) or ultrasound.
Radiofrequency systems use small electrodes to deliver controlled thermal energy in multiple spots around the circumference and length of the artery. Ultrasound-based systems use a balloon-tipped catheter to deliver 360-degree circumferential energy to the vessel wall, often with a cooling system to protect the inner lining.
The goal is to ablate the nerve bundles without damaging the renal artery itself. The physician repeats the process in both kidneys to ensure maximal denervation before removing the catheter and closing the access site.
Patient Suitability and Selection Criteria
The RDN procedure is intended for individuals whose hypertension is considered “resistant” or uncontrolled despite conventional treatment. Resistant hypertension is defined as blood pressure that remains above a target level, often 130/80 mm Hg, despite the concurrent use of three or more different classes of antihypertensive medications, including a diuretic.
Before considering RDN, a thorough evaluation confirms the high blood pressure is not due to non-adherence to medication or a secondary cause. Patients must undergo screening to rule out other conditions, such as primary aldosteronism or renovascular disease.
Anatomical suitability is a major consideration, as the renal arteries must be free of conditions like severe stenosis, or narrowing, that could complicate the procedure. Patients with severe kidney impairment, typically an estimated glomerular filtration rate (eGFR) below 40–45 mL/min/1.73 m², are generally excluded.
Expected Outcomes and Long-Term Monitoring
The most important result of RDN is a reduction in both systolic and diastolic blood pressure, although the magnitude of this effect can vary among individuals. Recent studies have demonstrated a sustained reduction in ambulatory systolic blood pressure, often by about 5 to 12 mm Hg, and diastolic blood pressure by about 3 to 9 mm Hg.
These blood pressure drops are often gradual, with the full effect of the procedure taking several months to fully manifest. RDN is an adjunctive therapy and not a replacement for all antihypertensive medications.
Most individuals continue to require medication post-procedure, though some may see a reduction in the number or dosage of drugs needed. Long-term monitoring is necessary to track the durability of the effect and ensure the patient maintains blood pressure control. Data shows effects lasting up to nine years.