New results from a clinical trial testing a novel ultrasound therapy for hypertension show the experimental treatment can deliver clinically meaningful reductions in blood pressure. The treatment is based on an old hypothesis that disrupting signals from overactive renal nerves can reduce systemic blood pressure.
Called renal denervation, the idea of treating hypertension by inhibiting renal nerve activity goes back more than 50 years, and some currently available medications for hypertension actually work by reducing renal nerve activity. So, many researchers have long worked to find a non-pharmacological way to target this mechanism.
In 2014, the results of a large blinded, sham-controlled trial concluded renal denervation does not reduce blood pressure compared to placebo. The influential trial dampened much enthusiasm for the experimental treatment. However, in the years that followed, improvements to the way the treatment is delivered and changes to the study methodology indicated renal denervation may still be effective.
A 2019 study following over 100 patients for six months after a single renal denervation procedure promisingly pointed to positive results. The simple surgical procedure involves threading a catheter up to the renal arteries via an artery in the leg. Ultrasound energy is then used to, “thermally ablate and disrupt the renal sympathetic nerves while sparing the renal arterial wall.”
This new study reports the results of a clinical trail testing the therapy on severe treatment-resistant hypertensive patients. The trial recruited 136 patients with high blood pressure despite being administered at least three different common antihypertensive medications.
Two months after the treatment, daytime ambulatory systolic blood pressure had dropped an average of eight points in subjects receiving the renal denervation procedure, compared to a drop of just three points in the subjects receiving a sham procedure.
"For patients with drug-resistant hypertension, a drop in blood pressure of eight points – if maintained over longer-term follow-up – is almost certainly going to help reduce the risk of heart attack, stroke, and other adverse cardiac events," explains Ajay Kirtane, co-principal investigator of the trial.
The treatment has not yet been approved for clinical use by the FDA. Further follow-up will monitor current trial participants for five years to investigate its long-term efficacy, and additional studies are still necessary to test the treatment in other patient populations before broader approvals can be granted, but the researchers are hopeful.
"These results suggest that renal denervation has potential to become an important add-on to medication therapy – including for those who have difficulty managing several medications to control their hypertension,” says Kirtane. "Additional studies will be needed to determine if this therapy may be effective for other groups, including older patients with hypertension and those with chronic kidney disease.”
The new study was published in the journal The Lancet.
