Killing nerves can reduce blood pressure

LOS ANGELES – A simple surgical procedure destroying certain nerves in the kidney can sharply reduce blood pressure in patients whose hypertension cannot be controlled with conventional medications, researchers said Wednesday.

The study was conducted on 52 patients whose blood pressure averaged 178/96, despite the fact that they were taking five separate hypertension medications. On average, their pressures dropped by 32/12, while a control group of 54 patients receiving only drugs showed no changes.

“Those blood pressure reductions are pretty remarkable,” said Dr. Douglas Weaver, division head of cardiovascular medicine at the Henry Ford Health System in Detroit, who was not involved in the study. “Those patients had been given everything and had not responded. … Did they prove that this (should go into the clinic)? No, the study is far too small. But they have shown that here is a way we could potentially lower blood pressure.”

An estimated 75 million Americans have high blood pressure, defined as a pressure of 140/90 millimeters of mercury or higher. Anything between 120/80 and 140/90 is considered borderline high. High blood pressure is one of the leading causes of heart disease and stroke.

Some studies have shown that reducing the systolic blood pressure (the top number) by only 6 millimeters of mercury can reduce the relative risk of stroke by 35 to 40 percent and the relative risk of a heart attack by 20 to 25 percent.

But an estimated 15 percent of those with high blood pressure are unable to control it, despite taking three or more medications. It is those people at whom the new treatment is aimed.

Researchers have known for decades that the sympathetic nervous system, which plays a role in the body’s “fight or flight” response, helps regulate blood pressure. Early attempts to control it with surgery produced severe side effects, and the efforts were abandoned when the first good anti-hypertensive drugs became available.

More recently, Ardian Inc. of Mountain View, Calif., has developed a system in which a small catheter is threaded through the groin and to the kidney, where radiofrequency energy is used to destroy the right nerves more precisely.

Dr. Murray D. Esler of the Baker IDI Heart and Diabetes Institute in Melbourne, Australia, led a trial of the device. The results were reported at a Chicago meeting of the American Heart Association and online in the journal Lancet.

The researchers found that only five of the 52 patients in the study did not respond to the treatment. For the rest, the mean systolic blood pressure after treatment was 146, and for 39 percent of the patients it dropped below 140, Esler said. The patients are still taking drugs, but some have been able to reduce their doses.