ROCHESTER, N.Y. (AP) – A 36-year-old woman with severe hypertension has been fitted with a pacemaker-like implant that, in limited trials in Europe, has shown promise in controlling wayward blood pressure through electronic stimulation of neck-artery nerves.

Annette Lawrence, a mother of three, has suffered for a decade from a chronic condition that a panoply of drugs and lifestyle changes has failed to alleviate.

But after Thursday’s surgery, the first of its kind in the United States, her elevated blood pressure readings dropped sharply, doctors said.

Surgeons at the University of Rochester Medical Center inserted a battery powered pulse generator under Lawrence’s collarbone along with tiny wires running up each side of her neck that stimulate nerves in the carotid arteries that play a role in regulating blood pressure.

“About halfway up the neck, these arteries have bulbs where there’s a lot of nerves that sense your blood pressure,” said Dr. John Bisognano, the team’s cardiologist. “We think if you stimulate these nerves, even in a normal person, blood pressure and heart rate will go down.”

Some 65 million American adults have high blood pressure, or hypertension, putting them at greater risk of stroke, heart attack, kidney failure and other problems. The risk is increased by old age, excess weight and lack of physical activity, experts say.

Developed by CVRx Inc., a private company in Minnesota, the experimental Rheos System device is designed for patients at grave risk of developing heart and kidney disease because of high blood pressure.

Tested extensively on animals over the last five years, the iPod-sized implant – 4 inches long, 3 inches wide and a half-inch thick – was placed in nine patients in Germany and Switzerland in 2003 and 2004.

All had systolic blood-pressure readings far above the ideal of 120 millimeters, but the implants have brought down those levels by an average of nearly 50 millimeters, said Dr. James Sloand, who performed the surgery on Lawrence.

In recent years, Lawrence developed kidney and other health ailments that forced her to quit her job as a health care technician. After the operation, which lasted a few hours, her systolic blood-pressure reading dropped from about 210 millimeters to about 160, Sloand said.

At least a dozen more volunteers with severe hypertension will have the device implanted at various hospitals around the United States over the next year. If found to be effective, a couple of years of randomized trials involving hundreds of patients would still need to be carried out before federal regulators approved the device, Bisognano said.

“Initially, we want to reserve this for patients who truly have blood pressure that can’t be treated with the available technologies, with drugs,” he said. “For every 20 points you drop your blood pressure, you cut your cardiovascular risk in half.”

Dr. Alan Weder, a professor of cardiovascular medicine at the University of Michigan at Ann Arbor, said the device “provides us with another approach, so I think it’s promising.

“My feeling would be that for the small number of people for whom we don’t have anything else to offer in terms of either lifestyle interventions or drug therapies, this I would say is the approach of last resort,” Weder said.