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Blood pressure (BP) reductions achieved with renal denervation remained clinically meaningful in people not taking BP-lowering medications, researchers found.

Hypertensive patients had more favorable changes in BP from baseline to 3 months if they had been randomized to renal denervation instead of a sham procedure in SPYRAL HTN-OFF MED:

• 24-hour systolic BP: -4.7 vs -0.6 mm Hg (P<0.001)
• 24-hour diastolic BP: -3.7 vs -0.8 mm Hg (P<0.001)
• Office systolic BP: -9.2 vs -2.5 mm Hg (P<0.001)
• Office diastolic BP: -5.1 vs -1.0 mm Hg (P<0.001)

These are "clinical meaningful BP reductions" in a trial powered to show that renal denervation lowers BP, according to a by Michael Böhm, MD, of the University of the Saarland in Homburg/Saar, Germany, at the virtual American College of Cardiology meeting for this year. The findings were simultaneously published online in the.

"In epidemiological studies, even a 2 mm Hg decrease in systolic BP is associated with a 10% reduction in stroke mortality and a 7% reduction in mortality from coronary or other vascular disease; therefore, the observed BP reductions in SPYRAL HTN OFF-MED are therefore quite relevant from a public health perspective," agreed Herbert Aronow, MD, MPH, of Alpert Medical School of Brown University in Providence, Rhode Island.

"The reductions in 24-hour ambulatory and office BPs were similar to those afforded by many commonly used antihypertensive agents, but unlike oral medications, renal denervation is 'always on' and not influenced by adherence, intolerance, or peak and trough levels," Aronow told MedPage Today. He was a site investigator for the trial but not involved in the analysis of the results.

SPYRAL HTN-OFF MED tested renal denervation using the multi-electrode Symplicity Spyral catheter to deliver radiofrequency-based ablations. The current analysis added the pilot and pivotal trial cohorts together for a total of 331 randomized participants.

"Because the Pivotal trial was much larger than the Pilot trial, it affords one the opportunity to evaluate treatment efficacy in multiple subgroups," Aronow said. "It is reassuring that the observed reductions in BP were consistent across all examined subgroups, including age, gender, and ethnicity."

On Bayesian analysis, renal denervation achieved >99.9% probability of superiority in 24-hour and office systolic BP, Böhm reported.

Additionally, consistent BP reductions were observed at night, when cardiovascular risk is highest, he said.

By 1 month, no patient experienced any major adverse events (all-cause mortality, end-stage renal disease, significant embolic events resulting in end-organ damage, renal artery perforation or dissection requiring intervention, vascular complications, or hospitalization for hypertensive crisis).

One hospitalization for hypertensive crisis occurred within 3 months after renal denervation, however.

To be eligible for the study, patients had to meet BP requirements through a robust screening process (office systolic BP 150-180 mm Hg and diastolic BP 90 mm Hg or above; and systolic BP 140-170 mm Hg on 24-hour ambulatory BP monitoring) and undergo drug testing to confirm that they were either drug-naive or had discontinued antihypertensive medications.

Investigators excluded people with unfavorable renal artery anatomy, low estimated glomerular filtration rate, diabetes (type 1 or type 2 with HbA1c >8.0%), and secondary causes of hypertension.

The final cohort had a mean age just over 52. About two-thirds were men, and one in five were African American. Baseline office BP was an average 162.7/101.2 mm Hg; 24-hour measurements were around 151.4/98.0 mm Hg.

SPYRAL HTN-ON MED participants were allowed to start BP drugs if office systolic BP was 140 mm Hg or higher at the 3-month mark. Furthermore, a safety escape was in place allowing patients to start BP drugs if office systolic BP exceeded 180 mm Hg at any time.

This safety escape occurred in 9.6% in the renal denervation group and 17.0% in the sham group within 3 months (P=0.049) -- potentially putting a dent in the observed treatment effect of denervation, Böhm suggested.

He noted that despite the off-medication protocol of this trial, antihypertensive drug use was detected in 36 patients. However, results were consistent between intention-to-treat and per-protocol analyses.

"Overall, a well done trial with impressive results ... The findings are convincing,"commented John Hirshfeld Jr., MD, of the Hospital of the University of Pennsylvania in Philadelphia.

Hirshfeld noted the "false starts" in early studies of renal denervation for hypertension. These studies, he said, had been limited by inadequate controls and lack of stability of blood pressure observations, as well as potential inadequate denervation from the earlier catheter designs.

"The investigators have learned from past experience and designed the SPYRAL HTN-OFF MED trial to satisfactorily control all the past sources of error. In addition, the SPYRAL ablation catheter is a different design developed specifically to address shortcomings of previously used ablation catheters," according to him.

A major unknown regarding renal denervation is the durability of its results beyond 3 months.

Thus, it is to be determined is whether the degree of BP reduction achieved in SPYRAL HTN-OFF MED will lead to long-term reductions in morbidity and mortality, Hirshfeld cautioned.

"It should also be noted that BP was not normalized. Thus renal denervation has the potential to be a partial palliation but not a cure," he added.

Since 2017, U.S. guidelines have called for a 130/80 mm Hg BP target for the general population.

Enrollment is ongoing for the pivotal cohort of SPYRAL HTN-ON MED, a complementary trial testing renal denervation in people staying on antihypertensive medications.

Ultrasound ablation is another technology being explored for renal denervation.

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