Renal denervation offers non-drug treatment to lower blood pressure
A sham-controlled trial of catheter-based renal denervation in patients with hypertension significantly reduced ambulatory blood pressure and office blood pressure in the absence of medications.
In the SPYRAL-HTN OFF MED trial, the primary efficacy end point of change in average 24-hour systolic blood pressure (SBP), adjusted for SBP at study entry, was –3.9 mm Hg lower in the arm randomized to renal denervation than in the sham control group. Similarly, the secondary efficacy endpoint of change in average office blood pressure, adjusted for office blood pressure at study entry, was –6.5 mm Hg lower in the treatment arm. Both end points measured the change in blood pressure from baseline to 3 months.
“The blood pressure [reduction] is clinically meaningful after 6 months and it is always ‘on’ and particularly at times of the day when the high blood pressure is most closely associated with cardiovascular complications,” said lead investigator Michael Böhm, MD, from Saarland University Medical Center, Hamburg, Germany.
SPYRAL HTN-OFF MED, an international trial conducted at 44 sites in 9 countries, enrolled 331 patients (80 from a pilot trial) with an office SBP 150 mm Hg or greater and less than 180 mm Hg and a mean 24-hour SBP of 140 mm Hg or greater to less than 170 mm Hg. Before double-blind randomization to the renal denervation or sham control group, patients were required to stop taking all antihypertensive medications for at least 3 weeks.
The mean age of patients was 53; 67% were men, about 20% were black, 16% were current smokers, and approximately 5% had type 2 diabetes. Slightly more than half had a hypertension diagnosis longer than 5 years. Mean body mass index was 31 kg/m1.
Renal denervation was performed using the Symplicity Spyral catheter, which is a multi-electrode catheter with quadratic vessel contact for simultaneous ablation in up to 4four electrodes. In the treatment arm, the mean number of main renal arteries treated per patient was 2.2 and the mean number of branches treated per patient was 5.8. The mean total number of ablations was 46.9 per patient. The procedure was successful in all patients.
There were no deaths, strokes, or changes in renal function in the treatment arm during the 3-month follow-up period, with one hospitalization for hypertensive crisis/emergency. There was one stroke in the sham control arm.
Some 17.0% of patients in the sham arm met the safety escape criteria (office SBP greater than 180 mm Hg or safety reasons), allowing them to be placed back on antihypertensive medication, compared with 9.6% of the treatment arm (P = 0.049). At baseline and 3 months, 85.1% in the treatment arm and 89.7% in the sham control arm had no evidence of antihypertensive medication use by testing of urine and serum.
Bayesian analysis showed a greater than 99.9% probability of superiority in the treatment arm versus the sham control arm on the primary and secondary efficacy end points.
The effect of renal denervation may have been underestimated in this trial, said Dr. Böhm, because previous studies have shown further blood pressure reduction after 3 months. In addition, an excess of patients in the sham arm who met the safety escape criteria may have limited the study’s ability to show the effect of renal denervation in the treatment arm.
Dhanunjaya Lakkireddy, MD, from the Kansas City Heart Rhythm Institute and Research Foundation, Overland Park, Kans., who was not involved in the study, commented that the reductions in blood pressure observed with renal denervation are “reasonably impressive for an antihypertensive study” but “are not enough to make a case for it to be a stand-alone therapy.” The true value of renal denervation, therefore, may lie as an adjunct to antihypertensive drug treatment.
A companion study, the SPYRAL-HTN ON MED trial, is testing the safety and effectiveness of renal denervation in patients taking up to 3 antihypertensive agents. It is expected to conclude in about 18 months.
- The SPYRAL HTN-OFF MED results were published simultaneously in The Lancet. Michael Böhm Disclosures: Consultant Fees/Honoraria: Amgen, Bayer Healthcare Pharmaceuticals, Boehringer Ingelheim Pharmaceuticals, Inc, Bristol-Myers Squibb Company, MEDTRONIC, Vifor; Other: Servier.