Reductions in blood pressure in treatment-resistant hypertensive patients who underwent catheter-based renal denervation persisted three years after the procedure, researchers said Oct. 23 at the Transcatheter Cardiovascular Therapeutics conference in Miami.
Hypertension is a risk factor for cardiovascular disease, and a third of adults in the U.S. are hypertensive, according to the American Heart Association. Approximately 10 to 30 percent of patients diagnosed with high blood pressure may fail to respond to three or more antihypertension drugs, though, said Markus Schlaich, MD, head of the Neurovascular Hypertension & Kidney Disease Laboratory at Baker IDI Heart and Diabetes Institute in Melbourne, Australia.
Renal denervation may offer promise as a treatment for hypertension in patients with persistently high blood pressure who do not respond to medications. In the catheter-based procedure, an interventional cardiologist, an interventional radiologist or an electrophysiologist uses radiofrequency ablation to disrupt nerves within the renal artery wall. The nerves are part of the sympathetic nervous system that affects organs that contribute to blood pressure regulation.
Schlaich presented three-year results of Symplicity HTN-1, which was designed to evaluate the safety and effectiveness of renal denervation. The study enrolled 153 patients with treatment-resistant hypertension with systolic blood pressure of 160 mmHg or higher who were on at least three medications for hypertension, including a diuretic. The trial recruited patients from 19 sites in the U.S., Europe and Australia. Researchers had data on 34 patients at the three-year follow-up.
“We wanted to be conservative,” Schlaich said. “That is why we used as a threshold not 140 mmHg but 160 mmHg systolic.” The lower 140 mmHg is the current systolic blood pressure threshold for hypertension treatment.
Among the 153 procedures, researchers reported no catheter or generator malfunctions and four complications, including one renal artery dissection during the catheter delivery and three access site complications. All were managed with no further complication.
At 18 months they reported progression of one pre-existing stenosis unrelated to the treatment and one new moderate stenosis that was not hemodynamically relevant and needed no treatment. There were no new reports of vascular complications or late adverse events at 36 months.
Schlaich and colleagues found favorable trends over time in the response rates and blood pressure reductions. The rate of patients with a reduction 10 mmHg or more in systolic blood pressure was 69 percent at one month and 94 percent at 36 months. Blood pressure reductions continued over time, from a mean of minus 19 mmHg at one month to a mean of minus 31 mmHg at 36 months.
The three-year data showed that the clinical response was sustained through three years and there was no loss of treatment effect over time.
Schlaich said the researchers believe there is a delayed treatment effect with renal denervation, perhaps related to arterial remodeling and a reduction in organ damage. But as yet there are insufficient data to support that theory.
“The longer we follow these patients over time, we see that the number of responders increases,” he said. “The other thing that supports this notion is that we seem to see gradual reduction in blood pressure. It doesn’t happen one day to the other, but rather at six or nine months.”
Concern that nerves targeted in renal denervation ablation may regrow and adversely affect blood pressure again may be allayed, at least in the three-year window, he said. “Having a sustained blood pressure reduction around 30 mmHg, which doesn’t change between two and three years, seems to indicate that there is long-term benefit of this procedure.”
He added the procedure is recommended only in treatment-resistant hypertensive patients. The Symplicity renal denervation system, which is made by Medtronic and was used in the study, is not approved by the FDA for commercial distribution. The trial was sponsored by Medtronic.