Renal denervation: the anti-hypertension operation?

Cardiovascular disease is a global burden, with a high number of deaths and disabilities. Hypertension is one of the main risk factors. It is even the #1 risk factor for stroke and heart failure. It is therefore in the patient's best interest, as well as in terms of public health, to manage it properly, with controlled figures (blood pressure < 140/90 mm Hg in consultation and < 135/85 mm Hg on self-measurement) to significantly limit the number of complications.
Recently, the specialized press and then the general public have been talking about a technique known as renal denervation, which could significantly improve the situation, or even treat hypertension definitively, by neutralizing the sympathetic nerves located in the arteries of the kidneys. Some messages even go so far as to suggest that hypertension could be cured: "one operation and no more drugs".
It's all very seductive: but what's the reality?

The sympathetic nervous system
The essential role of the sympathetic nervous system in the regulation of blood pressure has long been known, and as early as the 1920s, surgical treatments were proposed to cut the sympathetic nerves in patients with severe hypertension, a technique also sometimes performed for severe damage to the arteries of the lower limbs and now fallen into disuse.
The sympathetic system is a component of the nervous system that accelerates the heart and causes the arteries to contract. Neutralizing it at kidney level enables the arteries to regain their normal diameter, and also plays a role in salt elimination.

Modern renal denervation.
Some fifteen years ago, a new technique appeared: renal denervation performed endovascularly, i.e. by intervening not surgically but by passing inside the arteries to "destroy" these sympathetic fibers.
After some encouraging results, scientists realized that the technique was unsatisfactory, and it was virtually abandoned.

Then came new materials with different techniques (radiofrequency, ultrasound or even alcohol), and new conclusive studies provided concordant proof of the efficacy and safety of renal denervation.

On the basis of these results, the US Food and Drugs Administration and France's Haute Autorité de Santé have approved the use of renal denervation by radiofrequency and ultrasound in 2023 and 2024 as an additional therapy in the management of uncontrolled severe arterial hypertension.

Renal denervation by endovascular catheter is therefore a non-medicinal treatment designed to bring down blood pressure sustainably (for several years). This procedure, currently recognized by the French National Authority for Health and the Sociétés Savantes, is recommended as an additional treatment for people with inadequately controlled hypertension despite several medications.
It is not an additional medication, but an interventional procedure that involves interrupting the electrical activity of nerves destined for the kidneys.
It is proposed as a complementary treatment to medication for uncontrolled hypertension.

In practice, how is renal denervation performed?
Renal denervation is performed under a short general anaesthetic, as the procedure is painful.
Special probes are inserted through the femoral artery in the groin into the renal arteries. These probes deliver a low-intensity electric current or ultrasound, which interrupts the nerve fibers without damaging the structure of the artery.

The procedure lasts about an hour, and all the equipment is removed with a dressing that compresses the point where the femoral artery has been punctured. The patient is monitored in hospital until the next morning, and can be discharged home after 48 hours in hospital.
A small dose of aspirin (75 to 100 mg) may be given for one month after the procedure.
Antihypertensive medication is maintained, including on the day of the procedure, unless contraindicated by the anesthetic, and is continued on discharge and adjusted during follow-up by the physician. Tolerance and safety are very good.

Is renal denervation effective in lowering blood pressure?
According to studies, renal denervation lowers systolic blood pressure by around 8 mm Hg, with better results in subjects under 60, whose arteries are more flexible.
The technique can therefore reduce blood pressure by around 10 mm Hg, i.e. "from 160 to 150 mm Hg". This is equivalent to the effect of just ONE drug, which can be eliminated by reducing it from 4 to ... 3, but the figures will be controlled.
The announced cure therefore seems illusory. One of the explanations for this is probably that we are arriving a little late, after years of progression of hypertensive disease, with repercussions that are all the more noticeable when hypertension is severe and poorly controlled. The impact on the arteries, among other things, by causing them to lose their suppleness, means that the disease is fixed and normal figures can no longer be achieved without treatment.
In September 2024, a group of experts from the Société Française d'Hypertension Artérielle (French Hypertension Society) published a new consensus on the appropriate use of renal denervation in the management of hypertension in adults.

For which hypertensives?
Patients must have:
- Treatment-resistant hypertension, resistance confirmed by 24-hour ambulatory measurement despite treatment with at least four antihypertensive agents (3 for European recommendations) with appropriate drugs, including a thiazide or related diuretic, administered at the maximum dose.
- Anatomy of the renal arteries enabling the procedure to be performed, and absence of significant calcifications of the abdominal aorta and renal arteries.
- Kidney function still "correct".
- No secondary arterial hypertension, i.e. with a cause demonstrated by an appropriate work-up (such as excess secretion of a hormone: aldosterone).
- The patient must have been informed of the benefit/risk ratio, and his or her preferences must have been taken into account.
- After discussion in a center specializing in the management of hypertension: European Center of Excellence (there are around ten in France).
In Europe, there are two special cases (which may be open to discussion):
Uncontrolled hypertension with severe "non-adherence" to antihypertensive treatment. Around half of apparently resistant patients do not take at least one of the antihypertensives prescribed.
Intolerance to antihypertensive treatment, leading to impaired quality of life

In France, the Haute Autorité de Santé has just issued an opinion on this procedure, indicating the framework for its reimbursement [2] :
The indication is:
"Ultrasound renal denervation, by transcutaneous vascular route: uncontrolled hypertensive patients despite a well-conducted treatment including at least one antihypertensive quadritherapy according to current recommendations and in the absence of identified secondary arterial hypertension.
The indication must be validated by Centers of Excellence in Arterial Hypertension throughout France, which have gone through the validation process of the European Society of Hypertension (ESH)".
Only under these conditions will the procedure be reimbursed by the French Assurance Maladie.

In conclusion:
At present, the regulatory framework reserves intervention globally for the most serious cases for which maximum drug treatment proves insufficient.
This is the case in many pathologies where treatment is the "last resort", the aim clearly being to limit its use.
And if we were to look at the problem from another angle, exactly the opposite: young or relatively young subjects whose hypertension has just taken hold with low figures are largely accessible to lifestyle modifications: reduced salt and alcohol consumption, weight loss, and regular physical activity. In these young patients, hypertension has not yet caused any damage, the arteries are perfectly supple, with no cholesterol plaque, and they are going to be "bothered" by taking a treatment. If an intervention, which has a very good chance of succeeding, were to spare them treatment, this would be "cured" hypertension, with a strong benefit for the patient (but who will continue to be monitored) and for medical costs. Perhaps this is something to think about...


References:
[1] Pathak A. et al. Renal denervation by catheter in the treatment of arterial hypertension: expert consensus on behalf of the French Hypertension Society. Arch Cardiovasc Dis. 2024 Sep 12:S1875-2136.
[2] Haute Autorité de Santé : Avis n° 2024.0011/AC/SED of January 18, 2024.