Lowering high blood pressure using implanted electronic

An implanted electronic device similar to a heart pacemaker can lower blood pressure by at least 20 points in hypertension patients who have failed treatment with most drugs, researchers reported this week at a New Orleans meeting of the American College of Cardiology.

By applying electrical pulses to the carotid artery in the neck, the device triggers the body’s baroreflex system, which causes the heart to pump slower, arteries to dilate and the kidneys to excrete more fluid.

A 20-point reduction in blood pressure is typically associated with a 50 percent lower risk of heart attack and stroke.

At least 2 million Americans are unable to bring their blood pressure under control, so the device could ultimately find wide use if its efficacy is confirmed in larger trials under way.

”These are patients we deal with all the time,” said Dr. William B. Knopfler of St. Joseph’s Hospital in Atlanta, who was not involved in the study. ”If we can mitigate or eliminate the use of drugs, this could be an important advance in the treatment of hypertension.”

This approach to controlling blood pressure was first tried more than three decades ago, but the equipment available then was too bulky to be practical.

The new device was developed by physiologist Robert Kieval, who founded CVRx Inc. of Minneapolis in 2001 to commercialize it.

The device, called the Rheos Baroreflex Hypertension Therapy System, has three components: two electrodes that attach to each of the carotid arteries in the neck, thin leads that are implanted under the skin to convey signals from the pulse generator, and a matchbox-sized pulse generator that is implanted in the chest under the collarbone.

An external controller is used to activate and adjust the device.

The surgical procedure takes about three hours and is performed under a light anesthetic so the surgeon can check the response of the body to placement at various sites along the artery, finding the one that provides the best response.

The battery currently lasts 18 to 24 months and is not rechargeable.

Dr. Peter de Leeuw of the University of Maastricht in the Netherlands reported on studies in 26 patients in the United States and Europe who received the device. The patients, with an average age of 52, had each failed to control their blood pressure with three different drugs, including a diuretic, and had a systolic blood pressure of at least 160 millimeters of mercury.

The systolic pressure is the upper number in a blood pressure reading. A normal pressure is 120/80 mm/Hg.

Six months after the implantation, the systolic blood pressure was reduced by an average of 21 mm/Hg, while the diastolic pressure — the lower number in a reading — was reduced by an average of 16 mm/Hg, de Leeuw said.

The researchers observed no significant side effects from the procedure, he added.

No one is quite sure why the receptors aren’t already ordering the brain to take action against the hypertension, said Nadim Yared, president and chief executive of CVRx. ”It could be a problem with the receptors, or with the brain receiving a signal.”

But by injecting additional information, ”We are tricking the brain into thinking the blood pressure is even higher,” and the brain responds, he said.

Yared said the company has recently begun a randomized, placebo-controlled trial of the device in 300 patients. The device will be implanted in all the patients but will be turned on initially in only half of them.

Source : www.montereyherald.com