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Heating nerves with ultrasound reduces high blood pressure

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New research shows that a technique called renal denervation may help relieve drug-resistant hypertension. Thomas Barwick/Getty Images
  • Drugs for treating high blood pressure (hypertension) do not work in around a third of patients who receive a prescription for them.
  • The kidneys help to regulate blood pressure by adjusting how much water they extract from the bloodstream.
  • A relatively new technique called renal denervation applies ultrasound to heat overactive nerves that transmit signals to the kidneys.
  • A new study suggests that the technique can lower blood pressure in patients with drug-resistant hypertension.

Hypertension is known as the silent killer because while the condition has few if any symptoms, it increases a person’s risk of potentially fatal heart disease and stroke.

The Centers for Disease Control and Prevention (CDC) report that although nearly half of all adults in the United States have hypertension, only about 1 in 4 of these adults have the condition under control.

In around a third of patients who take antihypertensives, the drugs either do not work, or patients fail to take them as directed.

In people with hypertension, the ability of the kidneys to regulate blood pressure by adjusting how much water they extract from the bloodstream may become compromised.

In 2019, Medical News Today reported a successful clinical trial of an alternative to drug treatment called renal denervation for people with mild to moderate hypertension.

Renal denervation reduces overactivity in nerves that carry signals from the central nervous system to the kidneys, which lowers blood pressure.

The technique involves inserting a flexible catheter through a small incision in the groin, then threading it into the artery that supplies blood to each kidney.

For several seconds, a device at the tip of the catheter sends controlled bursts of ultrasound (high-frequency sound waves) into the tissue surrounding the artery.

The pulses of ultrasound heat up and damage some nerve fibers close to the kidney, reducing their activity.

A clinical trial by the same team of researchers now suggests that renal denervation can reduce blood pressure in patients with moderate to severe hypertension who do not respond to drug treatment.

“There are a variety of effective medications for lowering blood pressure, but many people need to take several drugs to control their hypertension, which can have side effects. In addition, many people simply don’t want to take additional medications and are poorly adherent to them,” says co-principal investigator Ajay Kirtane, M.D., professor of medicine at Columbia University Vagelos College of Physicians and Surgeons in New York, NY.

“It’s clear that we need additional therapeutic approaches to help patients get their blood pressure under control,” adds Prof. Kirtane, who is also a cardiologist at NewYork-Presbyterian/Columbia University Irving Medical Center.

The research, led by scientists in France and the United States, appears in The Lancet.

The authors also presented the results of their trial, called RADIANCE-HTN TRIO, to a virtual conference of the American College of Cardiology on May 16, 2021.

The researchers recruited 989 patients in the U.S. and Europe with blood pressure readings of at least 140/90 systolic/diastolic pressure in millimeters of mercury (mmHg) despite taking three or more drugs for controlling hypertension.

They switched all the patients to a single pill containing a combination of three antihypertensive drugs.

After 4 weeks, the researchers randomly assigned 69 patients whose blood pressure remained at least 135/85 mmHg to receive ultrasound renal denervation and 67 to a “sham procedure” that did not involve ultrasound.

After 2 months, the blood pressure of the patients who had the real procedure was significantly lower on several measures than that of patients who received the sham treatment.

For example, “ambulatory” systolic blood pressure (measured by a wearable monitor at regular intervals throughout the day) had a median decrease of 8 mmHg on average in patients who had renal denervation and by 3 mmHg in patients who had the sham procedure.

Nighttime systolic blood pressure had a median decrease of 8.3 mmHg in the treatment group compared with 1.8 mmHg in the control group.

There were no differences in adverse effects between the two groups, which suggests the ultrasound treatment is safe.

“For patients with drug-resistant hypertension, a drop in blood pressure of 8 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.”

– Prof. Ajay Kirtane, M.D.

“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,” he adds.

To assess the longer-term safety and efficacy of the procedure, the researchers will follow up with patients for 3 years.

Previous research suggests that repeat procedures will be unnecessary to maintain the effect on renal nerves.

“Renal nerve regrowth has been shown experimentally after [renal denervation], but their functionality remains very uncertain,” co-principal investigator Professor Michel Azizi from the AP-HP Hôpital Européen Georges-Pompidou in Paris, France, told MNT in an email.

The researchers are confident that patients’ bodies retain their ability to regulate blood pressure safely following the procedure, which doctors have now performed on thousands of patients worldwide.

“[T]here are multiple redundant biological systems which act in concert to regulate our [blood pressure], and the perfusion of our major organs, especially when our body is put at risk,” said Prof. Azizi.

The paper concludes that while adverse events were infrequent, “longer follow-up of this trial and more treated patients will be necessary to provide additional safety data.”

ReCor Medical, which makes the renal denervation device, sponsored the trial.

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