How a minimally invasive procedure is transforming hypertension treatment [PODCAST]

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Join us as we discuss the global epidemic of hypertension with cardiologist Jeremy Bock. With over a third of the adult population affected and traditional treatments missing the mark for millions, Jeremy dives into the challenges of controlling high blood pressure and explores innovative solutions. Learn about the renal denervation (RDN) system—a new, minimally invasive procedure that offers hope for patients who struggle with conventional methods.

Jeremy Bock is a cardiologist.

He discusses the KevinMD article, “Renal denervation: a solution for hypertension patients worldwide.”

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Transcript

Kevin Pho: Hi, and welcome to the show. Subscribe at KevinMD.com/podcast. Today we welcome Jeremy Bock. He’s an interventional cardiologist. Today’s KevinMD article is “Renal denervation: a solution for hypertension patients worldwide.” Jeremy, welcome to the show.

Jeremy Bock: Thanks for having me. I really appreciate the invitation.

Kevin Pho: So let’s start by briefly sharing your story and journey.

Jeremy Bock: So, yeah, I’m an interventional cardiologist. I practice outside Washington, D.C., and have been in practice for about eleven to twelve years. Back even when I was a trainee, I was really interested in the interactions between cardiac and renal physiology, and renal denervation, which was first developed about fifteen to twenty years ago, really married those two interests. I worked on the initial versions of the renal denervation catheter as a cardiology, interventional cardiology fellow, and have followed the story for many years. I was excited about being an early adopter and incorporating it into my practice now that it’s ready for prime time.

Kevin Pho: All right, so let’s talk more about that. You wrote that, of course, in your KevinMD article, “Renal denervation: a solution for hypertension patients worldwide.” So tell us about that article. Tell us about the procedure for those who didn’t get a chance to read your article.

Jeremy Bock: Yeah, so just for background, in the United States alone, they estimate about 48 percent of the adult population has high blood pressure, which is about 120 million people. We also know that blood pressure is the most common contributor to heart attack, stroke, and cardiac death. Clearly, better control needs to be a priority, because of those 120 million people with high blood pressure, we estimate that less than 25 percent are controlled according to our current practice guidelines.

And so clearly we need a new way of approaching this, because many patients who aren’t controlled, it’s because either the medications are not effective or they’re not taking them. There are adherence issues, and we know that in general, the more antihypertensive medications that are prescribed, the less adherent patients are. And so we need a new way of approaching this. From a public health standpoint, this has the potential to impact a ton of patients.

Kevin Pho: Perfect. So take me through some of the physiology. It’s been a while since I’ve studied this. Just for those who, it’s been a while, or just not remembering it, tell me a little bit about the physiology behind the procedure.

Jeremy Bock: Sure. So what you should know is that the renal sympathetic nerves that touch down on the renal artery and course as a web along the renal artery really lie at the crossroads to the major blood pressure control centers in the body. And so these renal sympathetic nerves serve as the main communicator between the brain and the kidneys. As we know, those sympathetic nerves, when they activate the kidney, there is, you know, blood pressure is regulated through a combination of salt and water handling and hormone output. Interrupting that crossroads was hypothesized to limit the body’s ability to launch a hypertensive response, and that turns out to be true.

With catheter-based renal artery denervation, we are aiming to selectively disable those nerves, and it’s irreversible damage because those nerves are unmyelinated, and so you do not see axonal regeneration. So when you impair those nerves, we think that it’s a permanent impairment. We are greatly interrupting the body’s control systems for launching a hypertensive response.

There are numerous potential ways of damaging those kidneys. I’ve been working with a technology that uses radio frequency ablation. The radio frequency energy generates heat, which selectively destroys the renal arteries without damaging surrounding structures. But there are also ultrasound-based platforms, which can damage the renal nerves, as well as alcohol ablation, which is in development. But really, our aim is to selectively and permanently disable those renal sympathetic nerves, which will interrupt the body’s way of causing high blood pressure.

Kevin Pho: And what kind of outcomes can one expect after undergoing this procedure?

Jeremy Bock: The pivotal trial that led to FDA approval showed a statistically significant blood pressure drop at six months. Not only was that blood pressure drop sustained, but it continued to grow out to three years, based on registry data that we have. And so based on the studies, anywhere between 15 to 25 millimeters of mercury drop in systolic blood pressure was the expectation.

Now, I have found in clinical practice, based on the non-research commercial patients that I’ve done, that that early blood pressure response is a lot more robust. Based on my single-center experience, if you take all the patients that we’ve treated here, we’re averaging about a 26 millimeter of mercury reduction just at six months. If you consider the fact that just lowering somebody’s blood pressure by 10 millimeters of mercury confers a 20 percent reduction in major all-cause cardiovascular events, a 26-millimeter drop is really pretty profound as far as risk to populations. Because we know that that response is sustained and continues out to at least three years, you know, it’s my expectation that the best is yet to come as far as treating these individuals.

The first goal of our program, of course, is to get blood pressure finally in the normal range. If that happens, we may have the opportunity to start cutting away the numerous blood pressure medicines these patients are on. Some of these patients are on five separate classes of antihypertensives, many of which are, you know, dosed multiple times per day. So it really is a burden. Part of me understands why non-adherence is so rampant: It’s because it’s really difficult to take that many pills on time every day without errors, especially in some folks that may have less health care literacy than others. So I really think that this is promising. It’s very, very exciting for our field.

Kevin Pho: So when you’re talking about an initial 20-plus-point drop in blood pressure, does that affect both systolic and diastolic equally?

Jeremy Bock: I don’t know if it affects it equally. The endpoints in the major trial were ambulatory systolic drops and office-based systolic drops. The diastolic does drop, but most of our data is on systolic blood pressure.

Kevin Pho: Realistically speaking, are you seeing patients come in with, say, four or five blood pressure medications, treatment resistance, and then after they leave the procedure, they can remove most of their blood pressure medications? Is that practically what we’re looking at?

Jeremy Bock: So we’re not seeing that yet. I will say that the early patients I’ve taken for this procedure are the patients that are the most severe examples of uncontrolled high blood pressure. So it’s not uncommon for me to have a patient that’s on five blood pressure medicines that has a systolic in the 170s.

It’s not a precipitous decline in blood pressure, and that’s probably a good thing, because that wouldn’t be safe. It would make it less predictable. We really like the slow and steady decline, so that we have the opportunity to see these patients for follow-up and have enough time to see that blood pressure decline and adjust medications as we need to, rather than that blood pressure just falling off a cliff in the week after the procedure. But we have seen a robust response, as I said, over the first six months, which is, you know, I think a reasonable amount of time, because often I’m seeing patients back in the office multiple times before that occurs. So I’m tracking that.

Kevin Pho: So in the studies looking at this, who were the patients that were being studied? Who were the cohort of patients?

Jeremy Bock: Yeah, great question. So the inclusion criteria were really limited to patients that had resistant hypertension, and that is defined as patients who have uncontrolled blood pressure despite the use of three or more meds, or their blood pressure is controlled, but it takes four, five, six medicines to achieve that control. And so that’s the definition of resistant hypertension.

The studies included patients that were eighteen years of age and older, met criteria for resistant hypertension, and had hypertension that was not attributable to a secondary cause like renal artery stenosis, hyperaldosteronism, pheochromocytoma, or Cushing’s disease. And so that was really the population that was targeted in the major trials, and in clinical practice, that’s the population that I’m targeting as well.

Kevin Pho: So you mentioned that there are FDA-approved devices for this. So where are we currently in terms of the availability of this technology?

Jeremy Bock: Yeah, great question. So the first two platforms for renal artery denervation were approved by the FDA one year ago this month, so November of 2023. There are two platforms that were approved. There’s a Medtronic device called the Symplicity Spyral catheter, which uses radio frequency energy to generate heat to destroy the nerves, and that’s one platform. The other platform is the ReCor Paradise system, which is an ultrasound-based catheter mounted on a balloon that uses ultrasound to selectively damage those renal arteries.

So those two devices have been approved now for a year. As is the case with a lot of new technology, it is not being reimbursed right now. So the people that are doing early commercial programs were doing most of it pro bono. My priority during this first year was not to make money but to start a program, just because of how enthusiastic I’ve been. This was a career goal for me, to be involved in something like this.

But the most recent news is that Medicare recently approved a transitional pass-through payment, so that the hospitals aren’t eating the cost of each of these procedures, and that is certainly a very big first step to being able to offer this therapy to a large group of patients.

Kevin Pho: So tell me about the patient experience. So this is an interventional procedure, obviously. What can the patient expect going through this procedure in terms of potential complications, and what exactly is the patient going to feel when that patient goes through this procedure?

Jeremy Bock: Right. So as an interventional cardiologist, almost all my procedures are minimally invasive. They’re catheter-based, so I’m not making an incision. I’m using a plastic tube called a sheath, and through that sheath, which acts as a port into the arterial system, I pass long plastic hot tubes called catheters and direct them to the area of interest, in this case the renal arteries. The entire procedure is catheter-based. And so when we’re finished, we just usually place a little plug where we went into the artery to seal that up, and the recovery is really minimal, because there’s no incision or blood loss to recover from. All patients that we’ve done here to date have had their procedures as outpatients and gone home the same day, and that’s really been a national trend for other people that have programs.

No implants are left behind. This isn’t like a stent procedure. What we’re doing is we’re using this specialized catheter to transmit radio frequency energy that’s going to turn into heat and damage the renal arteries. Our goal is to treat all renal arterial segments that are between 3 and 8 millimeters wide, just because that’s where the catheter contacts the intimal wall of the artery, but it’s not too small that the artery will spasm during the application of radio frequency energy.

A lot of patients will experience discomfort. They describe it either as a tightening or aching in their flank regions, but that is usually well tolerated using standard moderate conscious sedation. So we’re giving them these sedative medicines and narcotic analgesia titrated to patient comfort. So far, all the patients that I’ve treated have been able to tolerate the procedure to completion and have had an unremarkable recovery.

Now, that is very similar to the national trends. If you look at publications, the rate of adverse events is extremely low. Adverse events include renal artery dissection, renal artery thrombosis, and further impairment of renal function due to contrast administration. We just haven’t really seen that. And so one thing that has been a constant through numerous multicenter, randomized, sham-control trials is that the adverse event rate was exceedingly low.

Kevin Pho: And physiologically speaking, after undergoing this procedure, the effects are permanent. There’s no reason to think that you need to have this again in the future.

Jeremy Bock: So we think it is permanent. I very briefly touched base on this earlier, but the renal sympathetic nerves are unmyelinated, so they don’t have that protective myelin sheath, and that affects their ability to regenerate. And so based on everything that we know, these nerves are not regenerating, and so we don’t expect that patients will need more than one procedure.

Kevin Pho: So as this technology evolves and more insurers reimburse it, I’m an internal medicine primary care physician. Tell me when I should be thinking about this in the back of my mind in the coming years. What kind of patient should I be looking for and think maybe renal denervation may be in their best interest?

Jeremy Bock: I think there are a lot of situations where a patient comes to you, and I mean, that’s why we go into this, right? We want to be helpful to patients. We want to make their life either longer or better, hopefully both. It’s a really lousy feeling as a clinician when a patient comes in with this problem and you’re sort of throwing up your hands, and you’re like, “I really don’t know what to do anymore, right? We’ve tried every single blood pressure medicine. Some of them are having intolerable side effects, some of them just don’t work, and you’re not getting any better. And I’m afraid that between visits, you’re going to have a hypertensive stroke or something like that.” It’s an awful feeling as a clinician to not be able to help a person that’s in front of you.

And so when you’re having an encounter with a patient that has resistant hypertension, based on the definitions we went over before, I think a referral for a procedural intervention is very reasonable at this point. I think that this is not meant to be a standalone procedure. This is an additional tool in our toolbox for treating patients that previously didn’t have a good option. And so our intention is not to get patients off all of their blood pressure medicines. The primary goal of this procedure, or of our program, is to fix blood pressure, whether that’s with medicines, whether it’s with lifestyle, procedures, or usually some combination of all of them. But I would say, if trying to figure out a reason to refer, I think if you’re at the limit of what you can do with a patient medically, then I think the next step is considering a procedural intervention.

In terms of the technique of the intervention itself, this is something that’s readily learned by most interventional cardiologists. So only a minority of interventionalists are doing this procedure right now, because it’s so new, and I think the reimbursement has affected our ability to incorporate this into our practice, right? The people that we work for don’t necessarily like, you know, eating the cost of everything. This gets very expensive, and if you’re in a private practice, this is going to eat into your margins. But I think with time, because hypertension is such a common problem and because there’s such a need for better control, once reimbursement is available, I think you’re going to see a lot more people adopting this into their practice, so they can offer this to a broad group of patients.

Kevin Pho: We’re talking to Jeremy Bock. He’s an interventional cardiologist. Today’s KevinMD article is “Renal denervation: a solution for hypertension patients worldwide.” Jeremy, let’s end with some take-home messages to the KevinMD audience.

Jeremy Bock: I would say high blood pressure really is the silent killer. It affects many, many people, half the U.S. population, over a billion people worldwide. Up until the present, we’ve really done a lousy job of controlling it, not because we don’t care, but because we’ve reached the limit of what medical therapy and lifestyle modifications, you know, have been able to offer some of these patients. I think now we have a brand new tool in our toolbox that can address these problems. This new technology has been shown to be safe across multiple randomized, sham-control, high-quality trials. And I think that in the coming years, you’re going to see more and more people incorporating this procedure into their practice, so that we can offer patients a solution to, you know, a very high-risk problem.

Kevin Pho: Jeremy, thank you so much for sharing your perspective and insight. Thanks again for coming on the show.

Jeremy Bock: Thank you for having me. It’s a pleasure.

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