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Device shows promise for drug-resistant hypertension

Using electrical pulses, it tricks the brain into thinking blood pressure is even higher, causing the body to take action.

March 26, 2007|Thomas H. Maugh II | Times Staff Writer

An implanted electronic device similar to a pacemaker can lower blood pressure by at least 20 points in patients with drug-resistant hypertension, researchers reported Sunday at the American College of Cardiology meeting in New Orleans.

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

A 20-point reduction in blood pressure is typically associated with half the risk of heart attack and stroke.

With millions of Americans unable to bring their blood pressure under control, the device could find wide use if its efficacy is confirmed in larger trials now underway.

"These are patients we deal with all the time," said Dr. William Knopf 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 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 main components: a matchbox-size pulse generator implanted under the collarbone; two lead wires that conduct energy from the pulse generator to each carotid artery; and an external controller used by doctors to activate and adjust the device.

Implantation takes about three hours. The patient is lightly anesthetized so the surgeon can check response to device placement at various sites along the arteries.

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

Dr. Peter de Leeuw of Maastricht University in the Netherlands reported on U.S. and European studies involving 26 people, with an average age of 52, who received the device. Each patient had a systolic blood pressure of at least 160 millimeters of mercury (mmHg) despite taking at least three hypertension drugs including a diuretic.

The systolic pressure is the upper number in a blood pressure reading; diastolic is the lower. A reading of less than 120/80 mmHg is considered normal.

Six months after the implantation, the systolic blood pressure was reduced by an average of 21 mmHg, and the diastolic was reduced by an average of 16 mmHg, De Leeuw said.

The researchers observed no significant side effects, he added.

No one is sure why the receptors don't already order 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 with the device, "we are tricking the brain into thinking the blood pressure is even higher," and the brain responds, he said.

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

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