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Zapping Kidney Nerves Lowers Stubborn High Blood Pressure

An experimental device that destroys nerves near the kidneys helped to lower blood pressure in people whose hypertension remained out of control despite treatment with an average of five drugs, Australian researchers report.

Nov. 17, 2010 (Chicago) -- An experimental device that destroys nerves near the kidney helped to lower blood pressure in people whose hypertension remained out of control despite treatment with an average of five drugs, Australian researchers report.

In a six-month study of about 100 people, systolic blood pressure (the top number) dropped an average of 32 points in people treated with the device on top of the best available medication. Diastolic blood pressure (the bottom number) fell 12 points.

In contrast, blood pressure readings remained at the same stubbornly high levels among people on medication alone, says Murray Esler, MD, of Baker IDI Heart and Diabetes Institute in Melbourne.

The findings were presented here at the American Heart Association’s Scientific Sessions 2010 and simultaneously published online in the Lancet.

Radio Waves Silence Kidney Nerves

The device uses radio waves to silence nerves leading into and out of the kidney. These so-called sympathetic nerves contribute to the development and perpetuation of high blood pressure, Esler says.

"This could revolutionize the way we treat medication-resistant hypertension," says Suzanne Oparil, MD, of the University of Alabama at Birmingham.

Drug-resistant hypertension -- blood pressure that remains above goal in spite of concurrent use of three or more drugs of different classes -- is on the rise, now affecting about 15% of Americans, Oparil tells WebMD. She was not involved with the study.

"Many patients are uncontrolled on four or five drugs and have truly refractory hypertension," she says. "If it cannot be controlled medically, it carries a high cardiovascular risk."

High blood pressure is the No. 1 risk factor for premature death worldwide. In the United States, about 75 million Americans have hypertension and only about two-thirds are treated.

How It Works

The new procedure involves inserting a catheter-based probe through a puncture in the groin and maneuvering it through blood vessels until it reaches the arteries near the kidney.

Once there, the device emits short bursts of low-power radiofrequency energy to deactivate nerves lining the artery. Each person gets four to six two-minute treatments.

A total of 49 people treated with the device plus medication and 51 treated with medication alone completed the new study.

At the start of the study, the two groups had nearly identical average blood pressures: about 178/98. Participants' average age was 58, and nearly all were white.

After six months:

  • 84% of patients treated with the device had at least a 10 point drop in systolic blood pressure vs. 35% of patients on medication alone.
  • Systolic blood pressure dropped to less than 140 in 39% of patients whose kidneys were zapped with radio waves, compared with 6% of patients on drugs alone. Systolic pressures below 140 are a goal when someone is on treatment except in patients who have diabetes or chronic kidney disease, where the systolic goal is below 130. A systolic blood pressure of 120 or below is the ideal goal for adults.
  • Twenty percent of patients treated with the device needed less medication by the end of the study vs. 8% of patients on medication alone. Eight percent and 10% of patients in the device and drug groups, respectively, needed an increase in medication.

 

Unanswered Questions

"These are much bigger effects than you would anticipate if a new drug was being tested, particularly in people who are resistant to drugs anyway," Esler tells WebMD.

There were no serious complications during the six months of the study.

Oparil says "while exciting," the study leaves many unanswered questions. Among them: how long the procedure keeps blood pressure in check, whether it will work in people who aren't white and in people with diabetes or lower blood pressures, and whether it is cost-effective, she says.

The device is already available in Europe, where it costs about $12,000 to $13,000, Esler says. A U.S. study is scheduled to start next year.

Asked if we can cure hypertension, he says, "That's a big task [and] probably still a dream. But at least we have a device moving in that direction."

Ardian Inc., which makes the device, funded the study.

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