Rat study shows that renal denervation helps to bring drug-resistant hypertension under control

February 9, 2016

Up to 10 percent of people with high blood pressure have resistant hypertension—high blood pressure that remains elevated despite treatment with at least three blood pressure medications. Now, researchers report in the American Journal of Physiology—Regulatory, Integrative and Comparative Physiology that renal denervation—a procedure that disrupts the nerves in the kidneys and prevents them from relaying signals—can treat hypertension, including resistant hypertension, when the nerves are completely blocked. This new study, conducted in rats, identified the specific nerves that had to be blocked to achieve the therapy's blood pressure-lowering effects.

Most clinical studies have shown that can lower high in drug-resistant cases, but a number have shown the procedure to be ineffective. Two types of nerves transmit signals between the body and the brain: efferent nerves, which relay signals from the brain to the body, and afferent nerves, which send signals from the body to the brain. Knowing which nerve to block for antihypertensive effects will help optimize the therapy and reduce possible side effects, the study's authors write.

The research team used a technique they developed to block afferent nerves only. They found that disrupting the afferent nerves did not lower in hypertensive rats. However, ablating all the nerves did, leading the researchers to conclude that disrupted efferent nerves caused blood pressure to decrease. The treatment's effect also did not depend on the severity of the blood pressure increase. Renal denervation lowered blood pressure when performed at either the early or late stages of hypertension. This observation is contrary to clinical trials in humans that supported that the effectiveness of renal denervation depended on blood pressure level, says John Osborn of the University of Minnesota and lead investigator of the study.

The key implication of this study is that "renal denervation does lower arterial pressure when the denervation is complete," Osborn says. The researchers were able to confirm that the nerves were completely ablated in this study. However, no measurement method to check for complete denervation in patients exists. According to Osborn, this could explain why a recent large-scale clinical trial, Medtronic's Symplicity HTN-3, failed when the smaller ones before it succeeded. "Although catheter-based renal ablation is now possible, catheter design needs to be improved since present catheters appear only to partially denervate the kidney. Clearly, it is also important to develop a method to assess the completeness of denervation at the time of the procedure."

Interestingly, a previous study by the research group with a different type of hypertensive rat found that that ablating the other nerves, the afferent ones, lowered blood pressure. The opposite findings show how complex hypertension is, Osborne notes.

Explore further: Renal denervation achieves significant and sustained blood pressure reduction

More information: Jason D. Foss et al. Differential role of afferent and efferent renal nerves in the maintenance of early- and late-phase Dahl S hypertension, American Journal of Physiology - Regulatory, Integrative and Comparative Physiology (2016). DOI: 10.1152/ajpregu.00408.2015

Related Stories

Study tests new therapy for treatment-resistant hypertension

June 28, 2012

(Medical Xpress) -- Treatment-resistant hypertension affects nearly 6 million Americans and another 94 million people worldwide and is associated with increased cardiovascular risk, including stroke and heart attack, as well ...

Radio waves to kidneys lower persistent high blood pressure

December 17, 2012

Directing short bursts of radio waves at nerves surrounding the kidneys lowered blood pressure for at least six months and up to one year among patients with hypertension that persists regardless of taking multiple medications ...

Recommended for you

Patching up a broken heart

June 19, 2017

It is almost impossible for an injured heart to fully mend itself. Within minutes of being deprived of oxygen – as happens during a heart attack when arteries to the heart are blocked – the heart's muscle cells start ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.