Dec. 18, 2012 -- People who can’t get their high blood pressure down with drugs may be helped by a new procedure that deactivates overactive nerves in the kidneys, a small study shows.
The procedure is already available in Europe and other countries. It’s being tested in the U.S.
It’s meant to treat people with a severe type of high blood pressure that’s difficult to control, even with multiple medications. People who develop this condition, which is called resistant hypertension, are at higher than average risks for strokes, heart attacks, kidney disease, and heart failure. Resistant hypertension affects about 1 in 11 people who have high blood pressure.
“We all have these patients. They’re very thin. They exercise. They eat right. They’re on four medications and it’s still very difficult to control their blood pressure,” says Varinder Singh, MD, chairman of cardiology at Lenox Hill Hospital in New York City.
“In those patients, you’re looking for another treatment method,” says Singh, who was not involved in the research. “I look forward to having this.”
The procedure is done under local anesthesia. Doctors make a small incision in an artery near the groin and use it to thread a catheter up to the kidneys. A machine then fires short bursts of radio waves to deaden the sympathetic nerves.
“The sympathetic nerves are the stimulant nerves of the kidneys. They are commonly activated in [high blood pressure],” says researcher Murray Esler, MD, PhD, professor and senior director of the Baker IDI Heart and Diabetes Institute in Melbourne, Australia.
When the nerves are overactive, they cause the body to retain too much sodium. Too much sodium drives up blood pressure, Esler says.
Testing the New Procedure
The new study is a continuation of a trial that assigned 106 patients to receive either the new procedure or usual care.
People were enrolled in the study if they were on at least three medications for high blood pressure and had a baseline systolic blood pressure, the top number, over 160, or over 150 if they had diabetes. Most continued to struggle with high blood pressure, despite taking an average of five different medications.
At the end of six months, people who got the new procedure, which is called renal denervation, saw their blood pressure drop from an average of 178/97 to 143/85, while people who continued getting usual care actually saw their high blood pressure climb slightly.
For the second phase of the study, researchers asked members of the comparison group if they wanted to try the new procedure. Most did.
Their results were similar to those of patients in the first treatment group. The majority of patients saw their blood pressure drop by at least 10 points. Average reductions for the group were even bigger, about 20 to 30 points for systolic blood pressure, the top number. Diastolic blood pressure, the bottom number, was also lowered significantly.
But most people didn’t see their blood pressures return to normal levels. Normal blood pressure is considered to be less than120/80.
Treatment is ‘Not a Cure’
“This is not a cure for hypertension,” Esler says. Most people with resistant hypertension will continue to need some medication, he says.
After the procedure, some people were able to lower the number or dose of the drugs they were taking, though the reductions weren’t significantly different between the treated and comparison patients.
For the most part, the procedure seemed to be safe. Two patients in the study experienced complications. In one case, the catheter went through the wall of the artery in the kidney. Surgeons controlled the bleeding with a stent. In another case, a patient was hospitalized after experiencing an episode of extreme low blood pressure. That patient received IV fluids and had their blood pressure medications adjusted.
Two other patients had episodes of extreme high blood pressure that required hospitalization after their procedures.
“We don’t want to overhype it, because this is a new procedure, but we have not seen anything really [negative] come out of this so far,” Singh says.
One question that hasn’t been answered yet is whether reducing blood pressure this way will lower the risk of health problems caused by high blood pressure, like heart attacks and strokes.
“We think that it will, because medication does that, but it’s just too early to say for sure,” Singh says.
The study is published in the journal Circulation.