Could a simple surgical procedure -- renal denervation -- help control your blood pressure? Perhaps, say experts, but so far it is typically only for use alongside blood pressure medications.
Renal denervation, or RDN, for high blood pressure has been getting a lot of attention since the FDA approved two devices in late 2023, but not everyone with elevated blood pressure can get it.
The procedure, which involves zapping nerves around the renal artery that feeds blood to the kidneys, appears best suited for those with uncontrolled or resistant hypertension.
Resistant hypertension is when someone either is unable to control their high blood pressure with three medicines, including a diuretic, at maximum tolerated doses, or they’re able to control it with four medications. Along with diuretics, which reduce blood pressure by helping the body eliminate water and sodium, other medications might include a combination of drugs designed to block certain hormones or relax the blood vessels.
It could also be useful for people who can’t tolerate these medications or who struggle sticking to a regimen. There, too, is promising but limited research suggesting it could be helpful for those with refractory hypertension, which is when someone is unable to control their blood pressure with five medications.
Overall, however, about 1 in 3 patients don’t get help from renal denervation, or RDN, according to studies.
“The biggest current downside to RDN is that it does not work in everyone, and we do not have a good way of predicting who will have a significant response,” says Naomi Fisher, MD, associate professor of medicine at Harvard Medical School and an endocrinologist who serves as director of hypertension services at Brigham and Women’s Hospital.
When it works, it’s not expected to replace someone’s medications and lifestyle modifications, but it could allow certain patients to reduce their medications or dosages. That’s important, says Fisher, who was involved in the trials for the two leading RDN technologies, Medtronic’s Symplicity Spyral and ReCor Medical’s Paradise systems.
“RDN is a valuable treatment option for people whose blood pressure remains uncontrolled despite best attempts at lifestyle modification and despite taking multiple antihypertensive medications,” she says.
It may also help patients who don’t want to add more medications to their treatment plan.
“Several studies have taught us that a significant proportion of patients with hypertension would prefer a one-time procedure to lower their blood pressure rather than taking an additional pill,” Fisher explains.
How It Works
The kidneys play a pivotal role in regulating blood pressure. When the kidneys’ sensory nerves – specifically, the renal afferent nerves, which carry information to the central nervous system – become hyperactive, it can lead to water and sodium retention and overproduction of a hormone that exacerbates both. This elevates blood pressure.
RDN addresses the overactivity. Though recently approved for hypertension, the technology is not new. The proof of concept was published in 2009, and it has been used in limited capacities to treat atrial fibrillation, a type of abnormal heartbeat, and pain from autosomal dominant polycystic kidney disease, a genetic disorder.
RDN requires an incision in the groin to reach the femoral artery. A specialist inserts a catheter into the artery, guides it to the renal nerves, applies pulses of energy to destroy the nerve endings (a process called ablation), and then removes the catheter and the energy source. It's typically an outpatient procedure, and patients can go home after a few hours of monitoring.
Destroying certain renal nerve endings can reduce the nerve activity, lowering blood pressure by 8-15 points, some studies show. Follow-ups at various waypoints ranging from six months to 10 years appear to show the procedure is safe and the blood pressure reduction lasts, though the follow-up studies had relatively small samples.
There are two primary ways to deliver the energy: radiofrequency in the Symplicity Spyral system and ultrasound in the Paradise system. Ablative Solutions’ Peregrine System, which uses dehydrated alcohol to destroy the nerves, and SoniVie’s Titus, another ultrasound device, are undergoing trials.
Aside from Paradise and Symplicity Spyral using different energy sources and catheters, “there are more similarities than differences,” says Ajay Kirtane, MD, professor of medicine at the Columbia University Irving Medical Center and director of Columbia’s Interventional Cardiovascular Care program.
They also produce similar outcomes, says Kirtane, who was involved in the Paradise trials. That is why the FDA approved both devices in back-to-back panels 12 days apart, he says. The agency approved them only for use alongside blood pressure medications. The FDA and several studies have called for more long-term data, and Kirtane would like to see more research on cardiac events and strokes, where high blood pressure is a known risk factor. Still, he sees a lot of promise in RDN.
“It’s good to have another tool to be able to treat blood pressure because we know so many patients in the U.S. and world who have elevated (blood pressure) and it’s uncontrolled,” he says.
Skepticism Remains
Fisher and Kirtane concede doubts about the technology persist. RDN is a new treatment for high blood pressure, “and some clinicians are inherently conservative in their approaches to new therapies,” says Fisher.
Many of those doctors recall earlier trials that had well-documented shortcomings in study design, as well as a 2014 trial in which RDN did not perform well and “temporarily fell from grace,” she says. But more recent rigorous, randomized, controlled trials show it to be safe and effective, especially in those with the highest baseline blood pressure.
“In other words, the higher the BP before (the) procedure, the greater the expected fall afterwards,” she says.
Though it’s not surgery, catheterization is still invasive and there are risks, Kirtane says. Those include bleeding, bruising, damaged blood vessels, dislodging and disseminating cholesterol plaque, and complications involving the contrast agent used in the procedure.
It’s also expensive for patients whose insurance won’t cover it. Most plans don’t, though the procedure could become more accessible as the Centers for Medicare & Medicaid Services is analyzing whether it should be covered. It’s expected to decide in July.
Andrew Foy, MD, a cardiologist and associate professor of medicine and public health sciences at Penn State College of Medicine, still has his doubts about the procedure.
“One challenge with the technology is, when it was being developed, the notion was that we would be using it for patients with resistant hypertension,” he says. “It’s arguable how many are resistant.”
False diagnoses may stem from a combination of inaccurate measurements, inadequate medication regimens, a refusal to take meds, or “white coat syndrome,” a fear of doctors that could elevate blood pressure when it’s being measured in the exam room.
Faulty measurements could affect as many as 1 in 3 patients, he wrote in a February article in Trends in Cardiovascular Medicine, and he told WebMD that as many as 50%-75% of patients diagnosed with resistant hypertension might not have actually have it.
Foy also has concerns about the studies. He agrees there were problems with the early studies’ designs, but even the more recent studies have issues, in his opinion. The most rigorous studies to date showed less impressive blood pressure reductions when medications were maintained, he says. He also worries about long-term safety, which is still being studied, as well as general safety if the procedure becomes more commonplace.
Foy has never found a need to recommend RDN to his patients, he says. When his patients are properly diagnosed as resistant and he confirms they’re adhering to appropriate medication regimens and lifestyle modifications, including salt restriction, his next line of therapy is a type of drug called a mineralocorticoid receptor antagonist, or MRA.
MRAs, he wrote in the journal article, “have the highest level of evidence for improving multiple components of BP. The evidence for RDN, on the other hand, remains limited in patients with resistance.”
While he’s heard anecdotes of RDN working better in some people and is open to the prospect that longer-term, better-designed studies with appropriate blinding, randomization, and sham control (in which the procedure is mimicked but not actually performed in a control group) might yield more convincing evidence, the present data doesn’t persuade him, he says.
“Anything in this space that is not maintaining blinding shouts that it should be ignored, frankly,” Foy says. “This was really meant for resistant hypertension or beyond, so the fact it confers an 8- or 10-point reduction in patients with regular old hypertension – I don’t think we think it’s curative. You’re not going to get off meds for life, so it’s sort of like: What’s the point?”
