Sham-controlled evidence
As previously reported, significant BP reductions at 6 months in SPYRAL HTN-ON provided proof of concept and helped revive enthusiasm for the procedure after failing to meet the primary endpoint in the SYMPLICITY HTN-3 trial. Results from the Global SYMPLICITY Registry have shown benefits out to 3 years, but sham-controlled data have been lacking.
The trial enrolled 80 patients with an office systolic BP of 150-180 mm Hg and diastolic of 90 mm Hg or greater and 24-hour ambulatory systolic BP of 140-170 mm Hg, who were on up to three antihypertensive medications.
Medication changes were allowed beginning at 6 months; patients and physicians were unblinded at 12 months. Between 24 and 36 months, 13 patients assigned to the sham procedure crossed over to denervation treatment. Medication adherence at 3 years was 77% in the denervation group versus 93% in the sham group.
At 3 years, the renal denervation group had significantly greater reductions from baseline in several ambulatory BP measures, compared with the sham group, including: 24-hour systolic (10.0 mm Hg), morning systolic (11.0 mm Hg), daytime systolic (8.9 mm Hg), and night-time systolic (11.8 mm Hg).
Renal denervation led to an 8.2 mm Hg greater fall in office systolic BP, but this failed to reach statistical significance (P = .07).
Almost twice as many patients in the denervation group achieved a 24-hour systolic BP less than 140 mm Hg than in the sham group (83.3%, vs. 43.8%; P = .002), Dr. Mahfoud reported.
“Although renal denervation appears to effectively lower blood pressure, participants in the renal denervation group did not quite reach guideline-recommended blood pressure thresholds,” Harini Sarathy, MD, University of California, San Francisco, and Liann Abu Salman, MD, Perelman School of Medicine, University of Pennsylvania, Philadelphia, point out in an accompanying editorial. “This result could have been due to a degree of physician inertia or differential prescribing of blood pressure medications for the intervention group, compared with the sham control group, wherein physicians might have considered renal denervation to be the fourth antihypertensive medication.”
The editorialists also note that nearly a third of the sham group (13 of 42) underwent renal denervation. “The differentially missing BP readings at 24 months for the sham group are a cause for concern, although the absence of any meaningful differences in results after imputation is somewhat reassuring.”
A 10 mm Hg reduction in BP after 36 months would be expected to translate to a significant reduction in cardiovascular outcomes, they say. The sustained reductions in several systolic readings also speak to the “always-on distinctiveness” that renal denervation proponents claim.
“In the stark absence of novel antihypertensive drug development, renal denervation is seemingly poised to be an effective supplement, if not an alternative, to complex antihypertensive regimens with frequent dosing schedules,” they conclude. “We look forward to results of the Expansion trial in providing more definitive answers regarding whether this translates to meaningful protection from target organ damage.”
Dr. Mahfoud observed that BP control worsened during the COVID-19 pandemic, which may have impacted BP results, but that in-person follow-up visits were still performed. Other limitations are a lack of information on patients’ exercise, diet, and smoking habits and that blood and urine testing assessed medication adherence at discrete time points, but adherence over an extended period of time is uncertain.
Dr. Mahfoud reports research grants from Deutsche Forschungsgemeinschaft and Deutsche Gesellschaft für Kardiologie and scientific support and speaker honoraria from Bayer, Boehringer Ingelheim, Medtronic, Merck, and ReCor Medical. The study was funded by Medtronic. Dr. Sarathy and Dr. Salman report no relevant financial relationships.
A version of this article first appeared on Medscape.com.