Renal Nerve Ablation: “We hope it will soon be included in the list of covered services by health insurance companies“

Patients, who suffer from hypertension despite undergoing drug therapy, according to a study that was conducted with the participation of the Department of Nephrology and the Institute for Radiology at the University Hospital Düsseldorf, Germany, may benefit from renal nerve ablation, a catheter-based denervation of renal nerves. 08/08/2011

Doctor Oliver Vonend; © University
Hospital Düsseldorf

MEDICA.de talked to Doctor Oliver Vonend of the Department of Nephrology at the University Hospital Düsseldorf about the new procedure, patient expectations and his hopes for the future of this procedure.

MEDICA.de: Doctor Vonend, why can hypertension result from kidney disease?

Oliver Vonend: This is due to the fact that the kidneys are a measuring instrument for our blood pressure. If the kidneys detect that the blood pressure is not like it should be, they can adjust it. Especially the renal nerves that stretch from the kidneys into the head are playing an important role in this.

MEDICA.de: Your department has monitored a study that shows: A catheter-based denervation of renal nerves may cause a lowering of blood pressure in patients for whom drug therapy was previously not effective. What mechanism or idea is behind this?

Vonend: The idea is fundamentally based on the knowledge of the sympathetic nervous system. That’s the system that you needed in the old days if a lion approached you for instance. You needed to come to your five senses very quickly. That is to say, blood pressure and pulse had to rise quickly so you were able to dash away from the lion. This is the original function of the sympathetic nervous system so to speak. We still recognize its function today, if for instance you want to turn left or right with your car and only at the last moment notice the bicyclist you almost ran over. That’s a feeling of shock that really shoots through you. But since we rarely need this system today, it can be too much for our body at times. And we are also not able to reduce it in the way people in the old days were able to do – and this can influence blood pressure.

Of course you can try to regulate the sympathetic nervous system with drugs – here you should mention beta blockers for instance, which are prescribed to a relatively large number of people to inhibit the system in its activity. But back to the kidney: Sympathetic nerve fibers also emanate from it, which is what gave way to the idea to surgically cut through them. The first treatment experiments of this kind already occurred several decades ago, which were still performed in open surgery back then. What’s new with our treatment is that we only work with a small catheter to cut through the renal nerves. This can be done without a major incision, so you can say that the technical conditions have changed and that’s why new options were created.

MEDICA.de: How does the surgery take place?

Vonend: This can best be compared to a cardiac catheter examination. For the most part there is one kidney blood vessel for each kidney. It is surrounded by renal nerves that you want to burn off. To get to the appropriate spot, you penetrate the leg artery in the groin and push a small wire up under radioscopy. To get to the kidney, you turn off 90 degrees at navel height into the so-called renal artery. When the wire has been placed, you can push a special catheter via the wire forward to the kidney. At the tip of the catheter is a heating element with which you are able to point by point perform a burn-off of the vascular wall and the renal nerves located inside. Per side you approximately attach four to five times to achieve a transection.

MEDICA.de: So the surgery is always done on both sides at the same time?

Vonend: Generally we always try to burn off both sides. There are rarely any exceptions, such as for instance if you are not able to push the catheter forward to the patient’s kidney due to an anatomical distinction, or if a large amount of calcium plaque constricts access.

MEDICA.de: Are renal nerves after the surgery forever cut off or can they possibly rejuvenate?

Vonend: That is a very good question, because we don’t exactly know. There are nerves that stretch from the spinal cord into the periphery, for example into the arms. If such a nerve is damaged, for instance due to an accident, it could definitely sprout again. For renal nerves that stretch from the kidney towards the head, it is different. Here we are fairly certain that nerves are no longer able to rejuvenate.

 
During the operation the patients
receive analgesics through a drip;
© panthermedia.net/Jeanette
Atherton

MEDICA.de: How do the patients experience the surgery?

Vonend: Without pain killers the surgery would feel sort of like a visit to the dentist – if he drills into your nerve. At the burn-off moment you experience pain. That’s why you get pain relievers during the treatment. But as soon as the surgery is completed, this is no longer needed and you no longer experience any pain.

MEDICA.de: Are there any side effects you need to count on?

Vonend: So far we know of none. There are no long-term experiences available yet. However, we don’t know whether side effects appear after three, four or five years in patients. But we can look back at patients who were treated two years ago – and from them we were not able to discover any side effects. In particular it was being checked whether the blood vessel might have changed in time after the surgery or whether there is a point of constriction in the blood vessel, but we have found nothing and everything was great.

MEDICA.de: Do patients come for regular checkups?

Vonend: Patients come back very regularly: The first time after a month, then after three months, then after six months. In the follow-up examinations we particularly check the blood pressure, but also renal blood flow. This is why it is also important that the surgery and the follow-up care are done in specialized centers to optimally look after patients.

MEDICA.de: Does a patient sometimes need to be retreated?

Vonend: No, thus far this has not happened. Admittedly it can happen at times – my guess is about 20 percent of a total of 45 of our treated patients – that the procedure does not achieve the desired result. Thus far causes for the failure of the therapy in individual patients could not be identified yet. In any case it is important before the surgery to look for treatable causes for high blood pressure such as renal insufficiency, sleep-related respiratory disorders or hormonal causes. If such an underlying disorder exists, it should be systematically treated.

MEDICA.de: If the surgery was a success: Do patients nonetheless still continue to take blood pressure-lowering drugs?

Vonend: This is a very important point and I am glad you mentioned it, since many patients actually think this surgery is an alternative to a treatment with medication. Unfortunately, this is not the case, because the blood pressure of patients is too high despite drugs! That is to say, with this intervention as a start we want to bring them within a corridor where blood pressure with the intake of drugs is somewhat normal and is no longer at an exorbitantly high systolic pressure between 160 to 170 millimeters of mercury. If you were to omit the blood pressure pills, the patients would again be outside of the corridor and would have blood pressure values that are too high.

MEDICA.de: Are there more studies planned for the future?

Vonend: I hope so, because although at the moment we are able to successfully perform the surgery, the compulsory and private health insurance funds don’t pay for it however. That is to say the total costs – just the disposable catheter alone adds up to approximately 4000 Euros – are paid by the hospital or the patient. Within a study, patients would have the benefit of the study sponsor incurring part of the cost. We hope that renal nerve ablation will soon be included in the list of covered services by health insurance companies.

MEDICA.de: Are there criteria for exclusion for certain patients?

Vonend: This can only be based individually on the patient. You can definitely treat a spry 76-year-old if there are no existing concomitant diseases that are too serious. This always assumes that the renal blood vessels are not severely changed. You want to avoid doing more harm than good with the catheter. Other reasons to initially not perform a renal nerve ablation are the already mentioned reasons for suspecting secondary hypertension causes. If there is an adrenal disorder, which leads to increased water and salt absorption, you will develop high blood pressure. Then it would not be recommended to perform a nerve ablation. At first you should strive to eliminate the underlying problem.



The interview was conducted by Simone Ernst and translated by Elena O’Meara.
MEDICA.de