28 July 2011

Implant may help resistant hypertension

For people with high blood pressure that medication can't control, a new implantable device shows promise, researchers report.


For people with high blood pressure that medication can't control, a new implantable device shows promise, researchers report.

The device, surgically placed just below the collarbone, sends a four- to six-volt electrical jolt to the carotid arteries. This is said to lower blood pressure through a process known as baroreflex activation therapy.

The device might help tackle a growing problem, said the lead author of the study, which was funded by CVRx Inc., the device's maker.

"We are seeing more patients with resistant hypertension these days," noted Dr John D. Bisognano, who is a consultant for CVRx Inc. and a professor of medicine in the division of cardiology at the University of Rochester. "There are a lot of heavier people. There are a lot of diabetic people. We are also realising that the available drug treatment can't solve the problem for everybody."

As he explained it, the pulses generated by the implant trick the body into thinking that blood pressure has spiked. In response, the body sends out regulators that cause blood pressure to fall.

The results of a new trial were presented at a meeting of the American College of Cardiology in New Orleans and are now being published in the Journal of the American College of Cardiology.

Implant for high blood pressure

The phase three trial included 265 patients whose systolic blood pressure (the top number in a reading) was high - an average of 179 mmHg, according to Bisognano. He said the patients were hypertensive despite taking up to three blood pressure medications.

Blood pressure readings higher than 140/90 mmHg increase the risk of heart and kidney disease, stroke and death, experts note.

In one group of patients the device was activated one month after implantation, while in another group activation of the device was delayed for six months.

The researchers looked at several factors over the course of the study. These included a reduction in systolic blood pressure at six and 12 months, the safety of the operation needed to implant the device, the safety of baroreflex activation therapy and the safety of the device itself.

At monthly visits, if a patient's target was not met, the voltage was upped to further lower blood pressure.

The device did work well in many patients, the researchers reported. During the first six months, 42% of those whose device was turned on got their systolic blood pressure down to 140 mmHg, compared with 24% of those whose device was not yet switched on.

In addition, there was a 40% reduction in the rate of problems caused by high blood pressure in the group whose device was turned on.

Baroreflex activation therapy and hypertension

At one year, with the device now active in both groups, 52% of the patients reached the blood pressure goal of 140 mmHg, Bisognano said. He added that while using the device patients continued to take their blood pressure medications as usual.

However, there was no further reduction in systolic blood pressure among patients who received baroreflex activation therapy for a year, compared with those who received it for six months, Bisognano's group noted.

There were some safety issues as well. Some patients had problems stemming from the placement of the electrodes in the neck, including permanent nerve damage and complications from the surgery itself. And although most patients (74.8 percent) had no problems, that rate was still below the 82% the researchers had been hoping for, Bisognano said.

Approval of the device by the US Food and Drug Administration is still years away, if ever. While a price tag for the device plus implantation is yet uncertain, Bisognano said he believes the treatment will be cost-effective given the cost of taking care of patients who suffer heart attacks or strokes from hypertension. And he noted that the device is currently being redesigned to use smaller implantable leads that should reduce surgical complications.

"This is a very promising device," Bisognano said. "It's something we are likely to see in the future."

Commenting on the study, Dr Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles, said that "of the 72 million adults with hypertension in the United States, between 20 to 30% may have hypertension which is resistant to conventional medical treatment."

Treating resistant hypertension

There have been active investigations of a number of experimental therapies designed to modulate the nervous system to improve blood pressure control for these patients, he said.

"Although this trial demonstrated a sustained lowering of blood pressure and evidence that once the device was implanted therapy appeared reasonably safe, the trial did not demonstrate a significant reduction in early blood pressure control and there were greater than expected complications placing the device (approximately one in four patients experiencing a procedure-related complication)," Fonarow said.

Still, "some patients did experience impressive reductions in blood pressure with the baroreflex activation therapy," he said. "Further prospective studies will be required to evaluate the safety and efficacy of this experimental therapy for resistant hypertension."

More information

For more information on high blood pressure, visit the American Heart Association.

(Copyright © 2010 HealthDay. All rights reserved.)


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Hypertension expert

Dr Jacomien de Villiers qualified as a specialist physician at the University of Pretoria in 1995. She worked at various clinics at the Department of Internal Medicine, Steve Biko Hospital, these include General Internal Medicine, Hypertension, Diabetes and Cardiology. She has run a private practice since 2001, as well as a consultant post at the Endocrine Clinic of Steve Biko Hospital.

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