subject: Zapping nerves in kidney drops high blood pressure [print this page] Zapping nerves in kidney drops high blood pressure
A simple surgical procedure that destroys certain nerves in the kidney can substantially reduce blood pressure in patients whose hypertension cannot be controlled with conventional medications, researchers said Wednesday (Nov.17,2010).
The study was conducted on 52 patients whose blood pressure averaged 178/96, even though 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.
The new treatment damages certain nerves and causes key arteries to permanently relax. The procedure was approved two years ago in Europe and is just coming into wider use as doctors there are trained in the procedure.
"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 and 1 billion people worldwide 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 dropping 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.
Even if the treatment doesn't wind up being a cure and is only partly successful, that's still beneficial because these people are at grave risk of heart attacks, strokes and death, and drugs are not helping them enough, said Dr. Elliott Antman, a Brigham and Women's Hospital cardiologist.
That the treatment also improves blood-sugar control makes it especially attractive for diabetics. "This opens up a dramatic new option for them," Antman said.
Researchers have long known the sympathetic nervous system, which plays a role in the body's "flight or fight" 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 antihypertensive drugs became available.
More recently, Ardian, of Mountain View, Calif., developed the system in which a small catheter is threaded through the groin and to the kidney, where radio-frequency energy destroys the correct nerves more precisely.
Dr. Murray 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.
The patients have been followed only for six months. But Esler noted that some in an earlier trial have been followed for as long as 2 1/2 years and their blood pressure have not gone back up.
The team found no acute damage from the surgery and no significant side effects, he said.
The procedure takes 40 to 60 minutes and will most likely cost about $10,000, according to the company. An overnight hospital stay will probably be necessary.
Ardian has been in discussions with the Food and Drug Administration, the company said, and will probably begin a larger trial of the procedure in the U.S. next year.
