Welcome to Dr. Warrick's podcast channel. Warrick is a practicing cardiologist and author with a passion for improving care by helping patients understand their heart health through education. Warrick believes educated patients get the best health care. Discover and understand the latest approaches and technology in heart care and how this might apply to you or someone you love. What I'd really like to talk about is renal denervation. Now, what does that mean? Well, what I'd like you to imagine is the aorta, which is the main blood vessel in the body coming out of the heart and coming out and then bending down and going down towards the legs, a bit like the handle, a bit like an umbrella actually, the handle coming up, curtain down and then going down. to the point of the umbrella pointing towards the legs. So the aorta is that big blood vessel. Running along the aorta are fantastic networks of nerves. We call these the sympathetic nervous system. And those nerves can help regulate blood pressure and drive some of the mechanisms that alter blood pressure, increase heart rate, increase blood pressure, because our sympathetic nervous system is the one that we use for fight or flight. Now imagine as our umbrella is coming down, it's giving off branches. Just below the diaphragm, it gives off two branches, one to each side, and that's to the kidneys. Now the nerve supply, the sympathetic nerve supply to the kidney is very, very rich because the kidney is really important in regulating blood pressure. because the blood pressure is the filtration pressure for the kidney. So it needs to maintain filtration to make sure it gets rid of the bits and pieces from the circulation that are waste products. So very closely tied. Anyway, turn of this millennia and before a group in Melbourne led by a professor Murray Esler speculated that the sympathetic nerves running along the renal arteries to the kidneys could be potentially contributing to elevated blood pressure. Interesting thought. Well, they started to do around, I think, the 1990s research on animal models about this and started to get some sense that that was the case. And lo and behold, in about 2007, They did their first renal artery denervation, which meant that they undertook a procedure which literally burnt or removed the nerves, the sympathetic nervous system, plexus, the network of nerves going out to the kidneys. And they did that in Victoria, in Australia, around about 2007. And it turned out, in fact, to be on... someone's grandmother so it was a lady with elevated blood pressure who they did that on and believe it or not this seemed to show some promise well the significance of that is that with that promise a number of trials were generated and they also developed catheters or little tubes if you like wires that get passed up from the leg up into the renal arteries on both sides and from the inside of the artery were able to derange or eradicate or destroy, if you like, the sympathetic nerves travelling along the renal arteries. Well, there were multiple trials, relatively small over a number of years, which started to point towards this intervention being really quite a cool thing. to do but it wasn't until a number of years ago where someone said we really need to show that this trial works compared to no treatment and because the trial has quite a lot of if you like placebo effect that could be attached to going through the procedure they actually set up a sham procedure as their control arm in the study and that study was done a number of years ago. It was called the Simplicity 3 trial, and it was absolutely instrumental in the progress of this renal artery denovation concept for treating high blood pressure to lower root. They randomized somewhere around 500-odd patients, and what they found was that... there was very little significant difference in the reduction of blood pressure seen in the active group where they literally burnt and destroyed the renal nerves versus the sham group where they just stuck in a tube and pretended to burn the nerves. Very disappointing for that area of research. Absolutely sat everyone back down on their seat, scratching their heads. and put the mockers on this technology for, well, basically until now. And so a number of years later, another trial has been done. And this time it's been done because the last trial, which was the sham procedure, which looked like this intervention wasn't helpful, had a number of problems with it. One of the problems was that they... catheters that they were using were not particularly standardized and not the easiest to use, and the operators who were using them didn't necessarily have a lot of experience. So it turned out that some of the people in this multicenter trial with 30, 40, 50 countries around the world who'd all contributed to this trial or study, some of the operators had maybe only done one two or three cases so didn't really have experience in delivering the um the technique to actually ablate the arteries properly so there was a lot of discussion saying well you know the the catheters are not easy to use the operators didn't know what they were doing obviously you're asking you're comparing poor technique to nothing and so anyway They've done another trial, and this trial is called the Spiral HTN trial, Spiral Hypertension Trial, sponsored by the manufacturer of someone who's got a device that literally sits in the renal artery. It's got a nice, like a pigtail curl on it, if you like, or a corkscrew curl. And that corkscrew curl means that the catheter is applied to the artery, the inside of the artery, and it... is able to effectively, simply, and without a great requirement for technique, deliver the impulses required to derange or damage the renal artery nerves, the sympathetic nerves running out to the kidneys along that artery. Well, that trial was released two days ago. They had taken 331 patients. They'd randomized 166. to a sham procedure and 165 to the active procedure. Well, they took people whose blood pressure was as high as 150, right up to 180. So these are people with real blood pressure. They looked at office blood pressures and they looked at 24 hour blood pressure monitor pressures as well. Well, it turned out. that after three months evaluating these people after their intervention, and I'll have to read some of this just to keep up with it all, the 24-hour blood pressure group showed an overall four millimeter of mercury systolic reduction. The office blood pressure group showed a 6.5 millimeter reduction in systolic hypertension. These results statistically confirmed that this particular intervention clearly works compared to no therapy in a sham controlled trial. So this is very positive data to support the use of this therapy into the future. We just have to watch and see where this space works very nicely. The study reported it was incredibly safe. There were no procedural complications. Importantly, that sort of blood pressure lowering, by the way, offers a 20% relative risk reduction of cardiovascular event for those individuals receiving that blood pressure lowering, which is pretty fantastic when you think about it. One of the things that I bang on about all the time is blood pressure. So this is a way that we can potentially... lower tablet burden, which could be good. So for recalcitrant people on lots of tablets, we may be able to add this in and just help with a bit more control. Interestingly, the study seemed to show that the diurnal variation, the day-night variation seemed to be enhanced and improved on the use of this particular technology. So there will be development in this space. is something that does lower blood pressure that's not a medication, which is pretty exciting for many people because we know lots of people hate taking tablets. I'm not sure it's going to be for everyone. I think it'll end up being for the tricky or the awkward or difficult patients to help us bring that blood pressure down. It's going to be interesting to see what the cost is. Hard to know if it'll be rebated by Medicare or not in the longer term. We just have to wait and see. It's possible though, because blood pressure is such an important deal in our community. And it's so common. Blood pressure is affecting about 25% of our population. So it's a really, really big deal. So an interesting space where we can look at renal artery denervation, the sympathetic nervous system, the fight and flight nerves running out to the kidneys that can have an impact. on keeping blood pressure up, we can literally eradicate or disrupt them and lower blood pressure. So a really interesting space. Look, as always, if you have any queries or questions, please let us know. Leave a note below and we can get back to you if you've got any ideas for any other presentations, please let me know. You have been listening to another podcast from Dr. Warrick. Visit his website at drWarrickbishop.com for the latest news on heart disease. If you love this podcast, feel free to leave us a review.
