‘Denerving’ new treatment for uncontrolled hypertension

The practice of Medicine can indeed be very humbling. Being an inexact science with no clear road signs of where to go, it can throw medical scientists into a maze in which they can’t find the way out.

Any new drug, procedure or intervention can go in any of the three directions—with life-changing beneficial effect, or no significant beneficial effect but no serious side effects also, or more harmful than beneficial effects. Just when scientists and researchers thought they have a breakthrough in their hands, another research could practically nullify all the positive results earlier researches have shown.

Such may be the case of denervation therapy of the kidneys for patients with resistant or difficult-to-control high blood pressure (BP).

High BP not controlled

Resistant hypertension is defined as high BP that is not adequately controlled to acceptable levels of less than 140/90 mm Hg, with three antihypertensive drugs given at optimal dosages. Ideally, a diuretic, which gets rid of the excess salt one takes in, should be included in the patient’s drug regimen.

Kidney or renal nerve denervation (RND) is a procedure that is being done in several centers abroad to treat patients with resistant hypertension. In this procedure, the nerves which supply the kidneys are sort of deactivated by a catheter inserted either from the groin or the wrist to the kidney arteries. The nerves in the arterial wall are “denerved” or killed using ultrasound or radiofrequency energy delivered through the catheter.

Next best thing

Just a few months ago, I was invited to be part of a conference faculty which discussed the promising results of kidney denervation therapy in Australia, United States, Europe and even in some medical centers in Asia including the Philippines. At that time there were already two cases done here at St. Luke’s Medical Center. The results in the two cases were reported to be effective in controlling the patient’s hypertension.

All the international experts in attendance virtually agreed that RND is the next best thing that happened in the treatment of hypertension. The procedure is not really complicated and offers a big opportunity to treat many resistant hypertensive cases and save patients from the life-threatening complications of uncontrolled hypertension. I figured, though, that the cost can be a major constraint for this procedure, but it shouldn’t cost more than the stents that some patients get when their arteries are clogged. And I’m sure all specialists will agree that severely elevated, uncontrollable hypertension could kill patients instantly just as clogged arteries would.

During the conference, I made an innocent comment during the panel discussion that the procedure does not appear to be ready yet for prime time. One misgiving I had with it—aside from the cost—was that there was no clear way of finding out if a successful denervation of the renal nerve had been achieved. It’s not like in stenting clogged heart arteries wherein one can immediately see the remarkable improvement in blood flow through the fixed arteries after deployment of the stent.

A ‘leap of faith’

In RND, it’s more a presumption, a “leap of faith” as I recall describing it during the conference. The drop of the BP could just be a “placebo effect.” Of course, all the other members of the panel disagreed.

After that conference in Singapore, the results of a very stringent study on renal nerve denervation came out. Called the SYMPLICITY HTN-3 trial, it enrolled 535 patients with uncontrolled systolic BPs more than 160 mm Hg despite treatment with three BP drugs at maximally tolerated doses. The 535 patients were subjected to renal nerve denervation or to a sham procedure  in a randomized fashion to rule out any placebo or purely psychological effect.

The results of the trial came as a disappointment, a sharp contrast to what practically everyone expected. After six months, the mean office systolic BP decreased by 14 mm Hg in the denervation group and 12 mm Hg in the sham group, a non-significant difference. There were also no significant differences in the diastolic BPs.

So for now, the tally sheet for renal nerve denervation in the treatment of hypertension has been changed. It’s not something we can confidently recommend to patients with resistant hypertension. We should go back to the drawing board and retry the basics in controlling the patient’s BP.

With all the potent and effective antihypertensive medicines we now have, we should be able to optimally control nine out of 10 hypertensive cases. In the remaining 10 percent, we should rule out secondary causes of hypertension, meaning that there’s something else causing the hypertension which if treated, could also control the BP. This may be a tumor in the adrenal glands, constriction of kidney arteries or some other hormonal issues.

Obstructive sleep apnea

Lately, we find quite a number of cases of obstructive sleep apnea—a problem usually in overweight and obese individuals characterized by heavy snoring and temporary but frequent cessation of breathing while asleep. This is a fairly common but undetected secondary cause of hypertension, and if it is properly treated with available devices used when the patient sleeps, the resistant hypertension is controlled dramatically.

Aggravating factors like a high salt diet; or intake of contraceptives or anti-arthritis drugs, or some weight-reducing agents including herbals containing mahuang or ephedra could be the culprit for the uncontrolled hypertension. In many instances, too, the patient is simply non-adherent or noncompliant with the treatment he or she was prescribed. Effective medicines are ineffective if they’re not religiously taken. The attending physician should look into these factors for poor control of the BP.

Sometimes, going back to basics makes more sense than thinking of something radical or aggressive in treating our patients.