Implantable Device May Ease Tough-to-Treat Hypertension
WEDNESDAY July 27, 2011 -- 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 realizing 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 in April at a meeting of the American College of Cardiology in New Orleans and are now being published in the July 27 issue of the Journal of the American College of Cardiology.
The phase 3 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 percent of those whose device was turned on got their systolic blood pressure down to 140 mmHg, compared with 24 percent of those whose device was not yet switched on.
In addition, there was a 40 percent reduction in the rate of problems caused by high blood pressure in the group whose device was turned on.
At one year, with the device now active in both groups, 52 percent 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 percent the researchers had been hoping for, Bisognano said.
Approval of the device by the U.S. 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 percent may have hypertension which is resistant to conventional medical treatment."
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 1 in 4 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."
For more information on high blood pressure, visit the American Heart Association.
Posted: July 2011