Zapping nerves helps control high blood pressure
Published Wednesday, November 17, 2010 1:06PM EST
For people who can't seem to get their blood pressure under control despite daily medication, an experimental new treatment may offer a new hope.
The treatment targets the nerves near the kidneys that help to fuel high blood pressure. "Zapping" these nerves with radio waves appears to help lower that high blood pressure.
In a new study, the procedure helped lower the systolic blood pressure -- the top number of the blood-pressure reading -- by an average of 33 points. That's a significant drop and a lot better than the 10-point drop offered by the most effective medications.
The treatment works because it "silences" nerves leading into and out of the kidney. Those nerves regulate the "sympathetic nervous system" -- the body's "fight or flight" hormonal response that causes blood vessels to constrict, and increases heart rate and blood pressure.
Procedures to disrupt these nerves had been shown in the past to lower high blood pressure, but those procedures were done with full surgery on the kidney. The research was abandoned with the advent of now commonly used beta blockers, diuretics and other blood pressure medications.
Yet not every patient can take the drugs and their effectiveness is limited.
This new procedure is done using a catheter pushed into a blood vessel in the groin, much like the angioplasty procedures for opening clogged heart arteries.
The catheter is fed through the blood vessels into the artery leading to the kidney. Once in place, doctors use the device to deliver short bursts of low-power radiofrequency energy to destroy nerves lining the vessel.
The denervation device is made by a company called Ardian Inc., which sponsored the study published this week in The Lancet.
The study looked about at 106 patients who had a systolic blood pressure of 160 mm Hg or more. (Healthy blood pressure is anything below 140 over 90.)
Half the patients were randomly picked to have the procedure in addition to their drugs. The other half took only medication.
After six months, blood pressure among those who got the treatment fell by 32 points on the top reading and 11 points on the bottom reading, pushing some into the near-normal range.
There was no change in the control group.
The researchers were pleased to report there were no side effects from the treatment.
But they note that it is not a cure, since even the treated patients still need to take at least some of their medications.
Dr. Peter Liu, a cardiologist at the Peter Munk Cardiac Centre in Toronto, says he's impressed and excited by the study findings. He notes that there are many Canadian patients who are resistant to blood pressure medications who could benefit from the procedure.
But he also notes there are still questions.
"This study demonstrates this simple procedure had an effect and was lasting for six months. The question is do these nerves grow back, or does the high blood pressure come back so that the patient will end needing more medications down the road?" Liu told CTV News.
"These will be important questions that need follow up. Can we improve the procedure and make sure it is long lasting?