December 20th, 2012

Is “Zapping the Kidneys” Miraculous?


 Fact or fiction?  According to the latest lay press, renal denervation is “a potential public health miracle,” and “zapping the kidneys with radio waves can safely and dramatically lower blood pressure . . . Reduction in heart attacks and stroke rates of more than 40 per cent is anticipated.”

The facts:  In patients with drug-resistant hypertension (HTN), renal denervation with the use of the Symplicity catheter system (Medtronic Vascular) results in sustained blood pressure reductions. Systolic blood pressure reductions of 25 to 30 mm Hg were durable when follow-up was extended to 2 years in the open label Symplicity HTN-1 study and to 1 year in the randomized Symplicity HTN-2 study.

The future:  In March 2013, a phase 3, multicenter (87 sites), prospective, single-blind, randomized, controlled study (Symplicity HTN-3) of the safety and efficacy of renal denervation in 530 subjects with uncontrolled HTN is expected to be completed. 

In addition, studies of renal denervation (using the Symplicity catheter system) for treatment of the following conditions is underway:

  1. Resistant HTN in India,* Germany, Czech Republic, France, Belgium, Norway
  2. Mild refractory HTN
  3. Resistant HTN in chronic kidney disease (Singapore)
  4. Resistant HTN and sleep apnea (Poland)
  5. Resistant HTN and metabolic syndrome
  6. Chronic heart failure (with* and without renal impairment)
  7. Diabetic nephropathy

* indicates industry sponsored studies.

Your thoughts:

Are you convinced of renal denervation’s safety and efficacy?

Would you refer your patients with resistant HTN for this procedure, or do you need more data?

Do you plan to perform renal denervation?

8 Responses to “Is “Zapping the Kidneys” Miraculous?”

  1. Joel Topf, MD says:

    A one time procedure that can knock 30 points of systolic off patients with resistant hypertension? Sign me up.

  2. Dan Hackam, MD PhD says:

    Avoiding a Western-style diet can be remarkably effective for lowering blood pressure, with reductions of >30 mmHg often achieved in SBP. That is likely because the modern diet in industrialized countries is so toxic and obesogenic, producing metabolic syndrome in 1 in 2 people (according to the latest NHANES data). It would be interesting to pit this approach against the renal denervation procedure – I think I know which one my patients would prefer however.

  3. Donald Hislop, MS MD says:

    50 patients with office SBP > 160 despite despite 3+ anti-hypertensive medications including one diuretic ,eGFR >45 were treated with renal artery sympathetic nerve radio frequency ablation without complications in 96% and showed systolic and diastolic BP getting better after 12 months following the ablation .(

  4. Leon Hyman, Ms M.D. says:

    This seems to be a variation of the sympathectomies done for hypertension in the late 30’s, 40’s and 50’s until chlorthiazide(Diurel) was released in January of 1959. As a student at un.of Michigan , I worked in the hypertension unit in the summer of 58. We had an emergency referral of a 31 year old man with a blood pressure of 320/190. The next day he had a sympathectomy removing approximately 40% of his splancnic nerves(the peet procedure, which worked 40% of the time. The Smithwick procedure removed 60% of the time but had a higher incidence of side effects especially orthostatic hypertension. A month later in the clinic on 0.25 mg of reserpine his BP was 140/90 and all evidence of malignant hypertension was gone.

  5. Dmitri V Vasin, MD says:

    Agree with Dan Hackam.
    Majority of patients and doctors would prefer interventions. Unfortunately so.
    From what we know so far with “zapping” we are only fixing a number. Not that it does not have obvious benefits. Look good in EMR. Looks good to the insurer and for performance bonus. Interventionalist get their schedule full again after (hopefully) slowing with renal and coronary interventions.
    BUT…is it good for the patients? Do they live longer? Does zapping prevent death, CVA, MI, CHF, blindness, dementia, renal failure? Does it do ANYHTHING good (for the patient) except making a number on BP monitor look better?

    Our understanding of pathophysiology of HTN, and its treatment is rudimentary at best. We got entire RAS system wrong (just look at outcome trials of ARBs, ARB/ACEI combos and Aliskiren, or ACCORD trial). I would hold the anticpatory excitement about the outcomes of the “zapping” trial. Apparently we were not very good in predicting the outcomes of interventions in the field of HTN lately.

    If anyone were looking for a quick, effective and cheap way to lower SBP by 30 points – I would recommend time-honored practice of bloodletting. Any barber can do it for a nominal fee. For those who desire longer term and more systemic effect I would recommend the other old docs favorites: emetics and purgatives. With regular use they not only decrease BP, but also make patients lose weight and improve all other components of metabolic syndrome. Outcomes of these interventions have as much data support as “zapping” currently. I am sure 200 years from now “zapping” would be looked as barbaric as bloodletting or tonsillar irradiation for children with sore throat…

    We – doctors are all direct beneficiaries of obesity epidemics. It fills our office schedules with patients, it fuels growth in our stock portfolios investments in food and sugary drinks companies, pharma, devices, hospital systems, nursing homes, dialysis, etc, etc. Is it making us “subconsciously” hypocritical in advising patient to take a pill or go and “zap” something – rather than put more effort into LSM? Is it why we are so ineffective with our “LSM counseling”? Should we disclose to our patents that our professional and personal financial success depends on them, as a group, continuing to be obese?

    “Eating less is bad for business”…Indeed.

  6. Dan Hackam, MD PhD says:

    Dr Vasin raises many interesting points. First, without long-term endpoint data, it is impossible to know whether renal denervation does anything more than, say, old-fashioned bloodletting (which has been relegated to use in only hemochromatosis and secondary iron overload conditions). So we should temper our enthusiasm and demand that the technology not be approved until those trials are completed. Second, it is far easier to schedule a patient for a ‘zap’ than to make sustained efforts at lifestyle modification, which can have equally dramatic effects on not just blood pressure but many other markers of metabolic syndrome, inflammation, microalbuminuria and visceral adiposity – as well as, judging from the STARS and LHS trials, hard events as well. Third, we don’t know whether renal denervation therapy is actually durable.

    I agree with the point that in 200 years, doctors may look back on this practice as barbaric overkill. Note that we no longer remove the kidneys in cases of malignant hypertension. But at that one time, that was a standard operating procedure for many cases of malignant hypertension due to renal artery stenosis.

    In the meantime, until history judges my approach as incorrect, I will continue to focus my efforts on lifestyle modification and judicious antihypertensive use.

  7. Vasilios Papademetriou, MD says:

    Definetely the procedure is promissing. Results so far indicate that it is safe, but more randomized , well controll data is needed!

  8. Vasilios Papademetriou, MD says:

    I think you both got it wrong. Nobody argues against judicious use of medication/diet and exercise, but renal denervation at least as of now is been advocated and tested for patients with “reststant Hypertension”. These patiwnts by definition ( strictly speaking ) do not respond to pharmacologic therapy-most of the patients in clinical trials take 4-7 antihypertensive meds and still are not controlled. The early data are very encouraging, 30-32 mmHg reduction in systolic BP is impressive and the safety of the procedure seems pretty good. The two feared complications -renal artery stenosis and worsenning of renal function have not materialized -so far. Caution however in interpreting the results is warranted. Just remember that only one controlled trial has been published-Simplicity II and even this was not blinded and thus open to bias. Go back and check on the Lancet article. Note that there is NO PLACEO effect. In my 3o years of clinical research in hypertension I have not seen one clinical studythat has NO placebo effect.Then – big discepancy between office BP and ABPM, makes the data soft (????) although published in Lancet. The bottom line is that yes the procedure is exiting and very promissing, but we need more , well controlled, sham design study results.