A minimally invasive surgical procedure that targets nerves leading to the kidneys could one day offer a safe way for some people to reduce their blood pressure medications.
Investigators have announced the 6-month results of an international clinical trial on the safety and effectiveness of renal denervation by ultrasound as a treatment for mild to moderate high blood pressure.
The findings featured recently at the American College of Cardiology Conference in New Orleans and in a study paper in the journal Circulation.
Surgeons carry out the procedure, which takes about 1 hour, under local anesthetic. It decreases activity in nerves that link the brain to the kidneys and carry signals that regulate blood pressure.
The 2-month results from the randomized, controlled trial had already shown that the procedure resulted in a more significant reduction in blood pressure, compared with a "sham operation."
None of the people in the trial took their blood pressure drugs during the first 2 months. They then resumed blood pressure medication in a managed way, as necessary.
Now, the more recent results reveal that the participants who underwent the ultrasound surgery maintained their reduced blood pressure for 6 months.
Compared with those who had the sham operation, fewer participants who had the surgery needed to resume blood pressure medication, and those who did required fewer drugs at lower doses.
"These results," says lead trial investigator in the United Kingdom Melvin D. Lobo, a professor at Queen Mary University in London and also of Barts Health NHS Trust, both in the U.K., "point towards an exciting future for this new technology."
Hypertension and kidney nerves
High blood pressure, or hypertension, is a growing global health issue. According to a report in The Lancet, between 1975 and 2015, the number of adults living with high blood pressure rose from 594 million to 1.13 billion.
Some people can keep their blood pressure under control by watching their weight, doing plenty of exercise, and maintaining a healthful diet. Others may need to supplement these measures with medication.
However, some people struggle to control high blood pressure even with lifestyle changes and medication.
The kidneys have a rich system of nerves for sending and receiving messages.
Scientists have discovered that overactivity in this system can raise blood pressure through its interaction with the body's sympathetic nervous system.
Renal denervation by ultrasound is a treatment that aims to relieve high blood pressure by disrupting the nerves leading to the kidneys.
The procedure involves inserting a device through a catheter in the groin to reach up into the artery of a kidney. The device emits ultrasound waves that then heat up and damage some of the nerve fibers that surround the artery.
6-month results look promising
The 6-month results report a comparison of the procedure with a sham operation in 140 people at 51 sites in Belgium, France, Germany, the Netherlands, the United Kingdom, and the United States.
After 6 months, 58 percent of those who underwent the procedure had maintained their lower blood pressure compared with 42 percent who had received the sham operation.
Overall, most of the participants needed to resume their medications to maintain blood pressure control. However, 35.8 percent of the renal denervation group were still not taking drugs at the 6-month point compared with only 15.5 percent in the sham operation group.
Those who underwent renal denervation also showed a greater reduction in blood pressure. After 6 months, the average reduction was 18.1 millimeters of mercury (mm Hg) in the treatment group and 15.6 mm Hg in the sham operation group.
There were no safety issues among any of the participants.
It is important to know that the company that manufactures the renal denervation device that the surgeons used in this trial also funded the study.
"If long-term safety and efficacy are proven in larger trials which are currently underway, we hope that renal denervation therapy could soon be offered as an alternative to many lifelong medications for hypertension."
Prof. Melvin D. Lobo