Resistant Hypertension Responds to Renal Denervation
SAN FRANCISCO—Renal denervation may provide safe and sustained reductions in blood pressure and pulse pressure for two years in patients with treatment-resistant hypertension, according to new data presented at the 28th Annual Scientific Meeting of the American Society of Hypertension.
“The use of renal denervation is an extremely promising approach to the treatment of patients with uncontrolled resistant hypertension,” said investigator John Flack, MD, Associate Chairman for Clinical Research at Wayne State University Health Center in Detroit.
Pooled two-year data from the Symplicity HTN-1 and Symplicity HTN-2 trials show impressive reductions in office systolic blood pressure (SBP) with a single renal denervation treatment to both renal arteries using radiofrequency ablation, Dr. Flack said. This intervention was equally effective in patients younger and older than 65 years.
The Symplicity HTN-1 and Symplicity HTN-2 trials involved the use of a percutaneous catheter-based approach to deliver low-power radiofrequency energy to the renal nerves, thus interrupting the renal efferent and afferent sympathetic pathways. In this analysis, 239 patients had treatment-resistant hypertension. At baseline, they had a mean SBP of 160 mm Hg and a mean estimated glomerular filtration rate of 45 mL/min/1.73m2. During the studies, all of the patients remained on their antihypertensive regimen; however, changes in their regimens were allowed as clinically indicated. The mean age of patients who received renal denervation was 57 years and the mean body mass index was 32 kg/m2. For these trials, treatment-resistant hypertension was defined as uncontrolled BP despite use of 3 or more antihypertensive medications including a diuretic.
At one month after renal denervation, BP had decreased by a mean 19/8 mm Hg. In 149 patients followed out to two years, BP had decreased by a mean of 29/13 mm Hg. In addition, 38.9% of 12 patients who had an SBP of 140-159 mm Hg at baseline had an SBP below 140 mm Hg at two years after treatment.
“Research into renal denervation is very important and timely,” Dr. Flack told Renal & Urology News. “First, this approach allows for very impressive reductions in both systolic and diastolic BP in patients who manifest persistently high blood pressures despite intensive antihypertensive drug therapy. The reductions in blood pressure do not appear to be dependent on the type of antihypertensive drug therapy prescribed. Second, the blood-pressure lowering effect is durable out to beyond two years with a single treatment. Third, there are other clinically relevant benefits of renal denervation other than simply BP lowering.”
Small studies have shown that sleep apnea and glycemic control is improved in patients who have undergone this procedure, he noted.
The adverse events observed in the two trials were similar to those commonly observed with percutaneous access and catheter manipulation within the arteries. “There was no change in kidney function as determined by estimated glomerular filtration rate,” Dr. Flack said. “Adverse events related to the procedure have been very modest and mostly related to post-procedure hypotension.”
Patients older than 65 tended to have a lower baseline diastolic blood pressure (DBP) and higher baseline pulse pressure than younger patients. Both groups, however, had similar significant drops in pulse pressure at 24 months: (-16.4 and -15.7 mm Hg for those younger and older than 65, respectively.
Significant reductions in pulse pressure were driven by reductions in SBP, which lowers myocardial wall stress and subsequent oxygen requirements, Dr. Flack explained. Lowering SBP even when DBP is in the normal range has been shown consistently to reduce cardiovascular risk in older patients with wide pulse pressure hypertension.“Two-year follow-up data, though impressive, is not enough to determine the long-term efficacy and safety of the renal denervation procedure,” Dr. Flack said. “Nevertheless, there is ongoing long-term follow-up of patients beyond two years, and ongoing larger and more tightly controlled trial (Symplicity HTN-3) that will enroll 530 patients with severe uncontrolled resistant hypertension, and planned future studies in less severe hypertension.”