Zapping Renal Nerves - A Breakthrough in Lowering Blood Pressure

In the U.S., high blood pressure, or hypertension, is controlled successfully  in only approximately one third of people treated for this condition. Many with hypertension remain uncontrolled despite taking three or more blood pressure-lowering medications. For these people, there may be new hope from a technique that zaps renal nerves in the kidneys using radiofrequency energy.

The prevalence and danger of hypertension

About 30 percent of Americans (more than 70 million people) over the age of 19 have hypertension. This is defined as a systolic blood pressure greater than 140 mm Hg and/or a diastolic blood pressure greater than 90 mm Hg (normal is considered 120/80 or lower). Hypertension affects about 67 percent of Americans over the age of 60 and is more prevalent among African Americans and people with diabetes. Why is this important? Because the dangers of hypertension are significant--leading to strokes, heart disease, and kidney damage.

New treatment involves destroying sympathetic nerves supplying the kidneys

The SYMPLICITY HTN-2 research trial, reported in the journal Lancet, enrolled 106 patients with systolic blood pressures greater than 160 mm Hg, despite taking three or more medications. They were randomly assigned to continue their usual treatment (control group) or to receive low-energy radiofrequency treatments to ablate (destroy) nerves to the kidney. The minimally invasive treatment involved the application of four to six blasts of radiofrequency energy along the length of each renal artery to destroy the sympathetic nerves that run along the arteries. The procedure is thought to work because activity of sympathetic nerves to the kidneys is an important contributor to the most common form of hypertension.

Effects of renal nerve ablation

In this research trial, after six months blood pressure had not changed in the control group while the average in-office blood pressure measurements had dropped by a remarkable amount for those receiving radiofrequency treatments--32/12 mm Hg in the renal nerve ablation group. In addition systolic blood pressure had fallen by 10 mm Hg or more in 84 percent of them. Still, only 39 percent of the group receiving treatment achieved blood pressure control. In other good news, there were no serious complications related to the procedure and no differences in adverse events between the two groups.

Results point to fewer strokes and heart attacks 

Further study is needed to ensure long-term maintenance of the benefits of renal nerve ablation. One helpful consideration is that the procedure could be implemented easily because of the experience interventional radiologists and cardiologists have gained with other procedures affecting the renal arteries.

Although this procedure would probably be restricted to those whose blood pressure has proven resistant to conventional treatments, it looks promising. Based on the observed extent of blood pressure lowering, early treatment could substantially lower their risk of stokes and heart attacks. It is also possible that renal nerve ablation would reduce the number or dose of blood pressure lowering medications and thereby decrease both their side effects and costs.