Sometimes hypertension is difficult to control even when several medications are prescribed. If three or more medications are needed, including one diuretic (a medication that causes the body to eliminate excess fluids and sodium through urination), and your blood pressure is still not under control, it is called resistant hypertension. About 30 percent of people with hypertension have resistant hypertension. People with resistant hypertension are at higher risk for stroke and heart attack.

There’s a new treatment under investigation for resistant hypertension. It is called renal denervation. Renal refers to the kidneys, which play a part in normal blood pressure regulation. Denervation refers to deadening some of the overactive nerves of the kidneys in order to help control blood pressure.

One way the kidneys normally help with blood pressure regulation is when the nerves that run in the arteries to the kidneys tell the kidney retain more sodium, increase the secretion of hormones that raise blood pressure (Renin), and decrease blood flow through the kidney. These changes raise the blood pressure. These nerves also send signals to the brain, which, in turn, causes the arteries in the rest of the body to tighten, raising blood pressure. Although doctors aren’t sure why, in some people the nerves are overactive and continually cause the arteries of the kidneys to tighten and keep blood pressure elevated despite three or more blood pressure medications. Renal denervation might help in these cases. Renal denervation is a new minimally invasive procedure that deadens (cauterizes) some of the nerves of the kidney that are involved in blood pressure regulation. Then the nerves can no longer tell the arteries to constrict, so this helps lower blood pressure.

During the procedure, a long tube called a catheter is inserted through a small incision in the leg and threaded through the femoral artery in the leg to get to the kidney arteries. Once the catheter is in the kidney artery, radio frequency waves, ultrasound or other technology are used to deaden some of the nerves involved in keeping blood pressure high. (Radio frequency waves are a type of energy, similar to x-rays or even light from the sun.)

Early studies have shown promising lower blood pressure results after the procedure. Average blood pressure was 30 mm lower six months after the procedure. However, this therapy is not yet readily available in the United States, although it has been approved for use in Europe and Australia. A rigorously performed trial in the United States failed to support the positive results of these earlier trials. The full details of this trial will be reported in the spring of 2014. Most likely, further research will need to be done to understand exactly who may or may not benefit from this therapy.

It is important to remember that renal denervation is a therapy in development specifically to help patients whose high blood pressure does not respond to other treatments, including lifestyle changes and medications.