TUESDAY, March 29 (HealthDay News) -- A technique that interrupts nerve signals between the kidneys and brain dropped blood pressure to normal levels in 39 percent of patients with drug-resistant hypertension, according to a small new study led by French researchers.

At 24 international sites, 106 patients with uncontrolled high blood pressure (hypertension) randomly received either oral medication or renal denervation treatment, a procedure that uses a catheter-based probe emitting high-frequency energy near the renal artery to deactivate nearby nerves. It was the first human randomized trial of its type, with U.S. experts hailing the results as exciting and "visionary."

Six months later, the patients who received the nerve block procedure had experienced an average systolic blood pressure drop of 32 mm Hg and a diastolic blood pressure drop of 12 mm Hg, the study authors said.

Half of the nerve block patients showed a measurable benefit, and 39 percent reached recommended blood pressure levels, said study author Dr. Marc Sapoval, professor of clinical radiology and chair of the cardiovascular radiology department at Hopital Europeen Georges-Pompidou in Paris.

The procedure also appeared safe, with a low incidence of local complications, researchers reported.

Prior to the study, all the participants had had resistant essential hypertension, which means that a doctor could not figure out what was causing their high blood pressure (a systolic blood pressure of 160 mm Hg or more, or 150 mm Hg in people with type 2 diabetes) and that three or more drugs had failed to control the condition.

While encouraged by the results, Sapoval noted that the research was funded by manufacturers of the catheters and generators used in the study, and that the study was small, cautioning that more and larger independent trials and patient follow-up should be done. According to background materials accompanying the study, the U.S. Food and Drug Administration is planning a trial of the procedure involving more than 100 U.S.-based interventional radiology teams.

Sapoval also stressed that the research is still experimental and that the procedure should only be done by interventional radiologists on carefully screened patients in controlled research and academic settings.

The research was scheduled to be presented Monday at the Society of Interventional Radiology's 36th annual scientific meeting in Chicago.

"If the results are confirmed, it will be a frequent procedure," Sapoval said. "If further trials show that patients with less severe hypertension can benefit also, the number of patients will be huge."

Why renal denervation works is not entirely clear, Sapoval said, but it appears to dampen overactivity of the sympathetic nervous system, which can trigger high blood pressure.

About 25 percent of American adults have high blood pressure, most of which has no known cause, said Dr. Kirk Garratt, clinical director of interventional cardiovascular research at Lenox Hill Hospital in New York City.

"If this technique works, I believe it will be used first in patients with very, very difficult blood pressure issues," Garratt said. "Blood pressure trouble is extraordinarily common, and the cumulative cost measured by the cost of medications alone is very substantial. But . . . poor control drives up the cost of health care overall."

Described as minimally invasive, renal denervation may be an outpatient procedure if it becomes commonplace, which could happen in several years, Garratt said.

"It's a very novel and advanced technique, but the technical aspect would be familiar and easily adopted," he said.

Dr. Barry Cohen, medical director of the catheter laboratory at Gagnon Cardiovascular Institute at Morristown Memorial Hospital in New Jersey, called the study participants' blood pressure reduction "really unbelievable," and hopes the treatment could decrease the risk of cardiovascular and kidney problems arising from high blood pressure.

When promising research such as this is reported, "we think it's a shoe that's going to fit every foot, but we know we always have to be cautious and there may be some pitfalls. I think this is extremely visionary and . . . groundbreaking," Cohen said.

Because the study is to be presented at a medical meeting, it should be considered preliminary until it is published in a peer-reviewed medical journal.

More information

The U.S. National Heart, Lung and Blood Institute has more information about high blood pressure.