Denervation of the renal sympathetic nerve may become an important new tool in the fight against resistant hypertension. Previously, the main results of the Symplicity HTN-2 trial demonstrated that in selected patients renal denervation resulted in a large and highly significant reduction in systolic blood pressure (BP) at six months. Now, longer followup from the trial, published in Circulation, demonstrates that the benefits at 6 months extend to one year, and that control patients who crossed over to renal denervation also experienced large reductions in BP.
For 47 patients with resistant hypertension, the reduction in systolic BP at one year (−28.1 mm Hg) was similar to the reduction at 6 months (31.7 mm Hg). For 35 control patients who crossed over to renal denervation after six months, mean systolic BP dropped from 190.0±19.6 before the procedure to 166.3±24.7 mm Hg. The authors reported one case of renal artery dissection in the crossover group, which was fixed with renal artery stenting, and one episode of hypotension, which was fixed with a medication adjustment.
The results, according to a clinical perspective accompanying the article, suggest that “radiofrequency ablation of renal nerves can significantly lower blood pressure in patients with systolic blood pressures >160 mm Hg with no loss of treatment effect through 1 year and thus may provide a safe and effective adjunctive therapy for treatment-resistant hypertensive patients.”
Comment: Excitement about renal denervation has been growing in recent years. At least some of the optimism may well be warranted. But, for now, the greatest danger is hype. Here’s the #4 item on the AHA’s list, released just this week, of the top advances of 2012:
“Disconnecting” the kidneys might be the key to treating high blood pressure
What does that mean, “the key to treating high blood pressure?” As an invasive procedure, renal denervation will never be more than a important therapeutic option after lifestyle and polypharmacy have failed. I applaud the AHA for highlighting this important new technology, but I think it should have used more cautious wording.
Get ready for much worse. Gullible or naive reporters and editors have already fallen into the trap. Here’s the headline and opening sentences of a story that appeared earlier today in TheStar.com:
Zapping kidneys with radio waves could cure high blood pressure, study finds
In what’s being described as a potential public health miracle, a new study shows that zapping the kidneys with radio waves can safely and dramatically lower blood pressure.
“It makes one dizzy to think about the next set of benefits that follow,” said Dr. Clyde Yancy, head of cardiology at Chicago’s Northwestern University.
This is almost a textbook example of how science and medicine stories should not be reported. It’s important to activate your BS detector whenever you see words like “cure” and “miracle” in a health story. Renal denervation is not a cure and it’s not a miracle. If things work out, it may represent a welcome and significant advance for some patients with resistant hypertension.
To be fair, the rest of the story contains some great quotes and perspective from Clyde Yancy. But by then the damage has been done. It’s impossible to be rational in the presence of cures and miracles. Of course, any reporter can slip at some point and buy into the hype. We’re not perfect. But it helps if the reporter has some prior knowledge and experience in the field. I’m assuming this reporter had little background in this field, since no experienced health reporter would describe renal denervation as “bathing the kidneys in radio waves.” It’s hard enough for physicians and grizzled journalists to figure this kind of stuff out. This is no spot for learning on the job.
But let’s not blame the reporter. He was probably just doing his job as best he could, on a deadline and with few resources. He should be congratulated for getting a good interview with Clyde Yancy. The larger problem here is the way most media treat health, medicine and science stories. Breakthroughs and cures aren’t everyday events, except in the filler pages of tabloids, and on news broadcasts and websites, where scientific inflation is an everyday occurrence. In this context, scientific reporting becomes, essentially, worthless. If everything is a breakthrough then nothing is a breakthrough.
Here is the press release from Medtronic:
One-Year Results from the Symplicity HTN-2 Randomized Controlled Trial Published in Circulation
Published data demonstrate the Symplicity™ renal denervation system provides blood pressure reduction in patients with treatment-resistant hypertension sustained to 12 months
MINNEAPOLIS – December 17, 2012 – Medtronic, Inc. (NYSE: MDT) today announced that one-year results from Symplicity HTN-2, the first randomized clinical trial investigating renal denervation, were published online before print in Circulation, the Journal of the American Heart Association. These data showed patients who initially received treatment with the Symplicity™ renal denervation system (n=47) sustained a significant drop in blood pressure (-28/-10 mm Hg [p<0.001]) compared to baseline at 12 months; these 12 month results demonstrate preservation of the benefit at six month follow-up (-32/-12 mm Hg). No device-related serious adverse events, no late vascular complications, and no significant decline in kidney function were reported at 12 months. The Symplicity renal denervation system is not approved by the U.S. Food and Drug Administration (FDA) for commercial distribution in the United States.
Also reported in the manuscript were 6 month results of 35 patients in the control group who received renal denervation after the primary endpoint was assessed at six months post randomization (referred to as the crossover group). The crossover group also showed a significant drop in blood pressure six months after the renal denervation procedure (-24/-8 mm Hg [p<0.001]). This decrease in blood pressure is similar to the blood pressure reduction in the initial treatment arm at 6 months.
“We continue to see positive results from the Symplicity HTN-2 clinical trial, demonstrating consistent, long-term blood pressure reduction with the Symplicity system in patients with treatment-resistant hypertension, who have a three-fold increase in risk of cardiovascular events,” said Murray Esler, M.B.B.S., Ph.D., principal investigator of the Symplicity HTN-2 trial and Senior Director of the Baker IDI Heart and Diabetes Institute of Melbourne, Australia. “These data further substantiate the clinical benefits of renal denervation with Symplicity over longer periods of time in this difficult-to-treat patient group.”
The Symplicity HTN-2 trial is an international, multi-center, prospective, randomized, controlled study of renal denervation in patients with treatment-resistant hypertension. One hundred and six (106) patients were randomly allocated in a one-to-one ratio to undergo renal denervation with previous anti-hypertensive medication treatment or to maintain previous anti-hypertensive medication treatment alone (control group) at 24 participating centers. Patients in the control arm of the study were offered renal denervation following assessment of the trial’s primary endpoint at six months following randomization.
Renal denervation therapy is a minimally invasive, catheter-based procedure that modulates the output of nerves that lie within the renal artery wall and lead into and out of the kidneys. The nerves passing to the kidneys are part of the sympathetic nervous system, which affects the major organs that are responsible for regulating blood pressure: the brain, the heart, the kidneys and the blood vessels.
ABOUT TREATMENT-RESISTANT HYPERTENSION
Treatment-resistant hypertension, defined as persistently high blood pressure despite three or more anti-hypertensive medications of different types including a diuretic, puts approximately 120 million people worldwide at risk of premature death from kidney disease and cardiovascular events such as stroke, heart attack and heart failure. Research suggests that nearly one third of treated hypertensive individuals are considered resistant to treatment.1
About the Symplicity™ Renal Denervation System
The Symplicity system’s catheter and proprietary generator and algorithms were carefully and specifically developed through years of clinical experience to accomplish the renal denervation procedure. The Symplicity™ renal denervation system was launched commercially in April 2010 and is currently available in parts of Europe, Asia, Africa, Australia and the Americas and has been used to treat thousands of patients with treatment-resistant hypertension worldwide.
The Symplicity renal denervation system consists of a flexible catheter and proprietary generator. In an endovascular procedure, similar to an angioplasty, the physician inserts the small, flexible Symplicity™ catheter into the femoral artery in the upper thigh and threads it into both renal arteries in turn. Once the catheter tip is in place within the renal artery, the Symplicity™ generator is activated to deliver a controlled, low-power radio-frequency (RF) energy routine according to a proprietary algorithm, or pattern, aiming to deactivate the surrounding renal nerves. This, in turn, reduces hyper-activation of the sympathetic nervous system, which is an established contributor to chronic hypertension. The procedure does not involve a permanent implant.
The FDA granted Medtronic approval for the protocol for SYMPLICITY HTN-3, the company’s U.S. clinical trial of the Symplicity renal denervation system for treatment resistant hypertension in August 2011. More information about HTN-3 can be found atwww.symplifybptrial.com.
In collaboration with leading clinicians, researchers and scientists worldwide, Medtronic offers the broadest range of innovative medical technology for the interventional and surgical treatment of cardiovascular disease and cardiac arrhythmias.
Medtronic, Inc. (www.medtronic.com), headquartered in Minneapolis, is the global leader in medical technology – alleviating pain, restoring health and extending life for millions of people around the world.
Any forward-looking statements are subject to risks and uncertainties such as those described in Medtronic’s periodic reports on file with the Securities and Exchange Commission. Actual results may differ materially from anticipated results.
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