This site is meant for educational purposes only no medical advice is given or implied. Renal denervation is still an experimental treatment in many parts of the world, including the United States.

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Renal denervation (RDN) is a minimally invasive catheter based endovascular procedure to ablate the renal nerves and disrupt the crosstalk (sympathetic signals) between kidneys and the brain. RDN is being studied around the world in different clinical conditions associated with an overactive sympathetic nervous system: hypertension, diabetes, obesity, apnea, and heart failure. Currently different RDN technologies have been approved in Europe and for phase III clinical trials in the USA . The FDA has approved clinical trials in the USA for both Symplicity TM and EnligHTN .
RDN is currently only approved for patients with resistant hypertension in Europe and Australia. In the USA, FDA has approved RDN only for investigational clinical trials in the treatment of resistant hypertension.

Uncontrolled High Blood Pressure

The Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC 7) guidelines for blood pressure goal is < 140/90 mm Hg in the general population and <130/80 mm Hg for patients with diabetes and chronic kidney disease. Failure to achieve this goal is defined as uncontrolled hypertension.

What is the Global Burden of Hypertension:

  • In 2000, 972 million (26%) adults had hypertension (high blood pressure) worldwide
  • In 2025 about 1.5 billion people (29%) are projected to have hypertension, with a significant increase in India and China 1
  • 1 in 3 adults in the US has hypertension and less than half have it controlled
  • In the USA alone, hypertension costs $131 billion annually in healthcare expenditures
  • Global Prevalence of Uncontrolled Hypertension:

    • Uncontrolled hypertension is associated with increased mortality
    • Treatment and control reduces heart attacks and strokes, heart failure, and chronic kidney disease, and can save lives
    • NHANES 2003–2010(USA):2
      • Prevalence of adult HTN: 30.4% (66.9 million)
      • Uncontrolled HTN: 53.5% of HTN patients (35.8 million)
      • 14.1 million unaware of HTN, 5.7 million aware but not on treatment, and 16.0 million aware and treated but remain uncontrolled
      • 85.2% of uncontrolled HTN patients had health insurance
    • Worldwide burden of Hypertension: 3,4
      • 7.6 million premature deaths each year attributed to high blood pressure
      • About 54% of stroke and 47% of ischemic heart disease attributable to high blood pressure
      • 80% of the attributable burden occurred in low-income and middle-income economies, and over half in population ages 45–69
      • England (1998): Aware 45%, Treated 32%, Controlled 9%
      • Germany (1995): Aware 60%, Treated 35%, Controlled 12%
      • Canada (1992): Aware 58%, Treated 39%, Controlled 16%
      • Spain (1990): Aware 45%, Treated 32%, Controlled 5%
      • China (2001): Aware 45%, Treated 28%, Controlled 8%
  • Resistant Hypertension

    The American Heart Association defines resistant hypertension as blood pressure that remains above goal (>140/90 for all patients, >130/80 for diabetes and chronic renal insufficiency patients) despite the use of maximum tolerated doses of 3 antihypertensive drugs (from different classes, one of which should be a diuretic) and compliance to lifestyle measures.1 High blood pressure that is under control but requires more than 4 antihypertensive drugs is also considered resistant hypertension. It is thought that 30% of the population with high blood pressure have uncontrolled blood pressure (per JNC 7 Guidelines). The National Health and Nutrition Examination Survey (NHANES) estimated a prevalence of resistant hypertension in 8.9% of all adults with hypertension and 12.8% of all drug-treated hypertensive adults in the US.5

    Race (non-hispanic black), obesity and old age were the risk factors for resistant hypertension.5 Patients with resistant HTN are more likely to have albuminuria, reduced renal function, and self-reported medical histories of coronary heart disease, heart failure, stroke, and diabetes mellitus (P<0.001).5

  • Prognosis of Resistant Hypertension

    So far there is no data that actually addresses the prognosis of resistant HTN; however there is a direct relationship with the level of BP and cardiovascular mortality. Furthermore, the risks of myocardial infarction, stroke, heart failure, and renal failure directly relate to the intensity of blood pressure.3

    Every 20/10 mm Hg increase in blood pressure is associated with more than a twofold increase in stroke and cardiovascular mortality. For example, a middle aged patient (between age 40 and 69) with a blood pressure reading of 175/105 mm Hg is 8 times (an absolute risk increase of 800%) more likely to die of cardiovascular mortality in the next 10 years in comparison to a patient of the same age/ethnicity/sex with a blood pressure reading of 115/75 mm Hg.6

    On the other hand even small reductions in BP translate into cardiovascular mortality benefit. A meta-analysis of 61 prospective, observational studies evaluating data of 1 million adults between ages 40-89 from multiple different countries and ethnicities showed that just by reducing the mean systolic blood pressure by 2 mm Hg translated into a 7% relative risk reduction of cardiovascular mortality and a 10% relative risk reduction of stroke mortality.6

  • Diagnosing Resistant Hypertension

    A patient may not have true resistant hypertension but continuously lacks adequate blood pressure control. This situation is also referred as “pseudo-resistance”. The following factors should be considered in diagnosing resistant HTN and prior to considering the RDN treatment:

    I – Physician Inertia and Medications:

    Definintion: The conscious decision by a clinician to not adequately treat a condition despite knowing that it is present: A phenomenon seen in American medicine that can be due to a lack of training and experience with antihypertensive agents.

    II –Physicians Tend to Undertreat Hypertension:

    Concern about side effects
    • Suboptimal dosing of antihypertensive agents or inappropriate combinations of agents is one of the major causes of inadequate BP control
    • Data from a hypertension specialty clinic showed that either by increasing the dose or initiating or switching to the proper
      diuretic was the most common change that achieved BP goal among patients referred for resistant hypertension7

    II – Compliance and Drug Interaction:

    Poor compliance to an effective antihypertensive regimen or life style measures is a major cause of apparent resistant hypertension

    • Discontinuation rate of antihypertensive drug is about 50% within 1 year
    • Once daily dosing can lead to more likelihood of compliance
    • Agents with low side effect profiles and improved communications with patients, cost of the medication and education of importance of achieving BP control help compliance
    • Large amounts of alcohol intake (3 or more drinks/day) have a dose-related effect on BP and patients should be limited to no more than 1 oz of ETOH (2 drink)/day for men and 0.5 oz of ETOH (1 drink)/day women.
    • Excess dietary salt is the most important culprit particularly from processed foods. Average sodium intake of resistant HTN patients exceeds 10 g/day
    • Dietary sodium for a hypertensive person should be < 100 mMol/day (2.4 g sodium or 6 g sodium chloride)

    III – Proper BP Measuring Technique:

    • Allow the patient to sit quietly for adequate time prior to measuring BP
    • Take mean reading of triple BP measurements
    • Use appropriate cuff size
    • No smoking at least 3 hours prior to BP reading
    • Arm at heart level

    IV – White-Coat Effect:

    • Higher office readings than at home or ambulatory BP
    • 25% of patients referred for resistant hypertension achieve goal BP under treatment when ambulatory measurements are performed
    • Patients with white-coat effect have less target organ damage compared with true resistant hypertension patients
    • Patients with “white-coat” HTN have significantly higher systemic muscle sympathetic nerve activity

    V – Secondary Cause of HTN:

    • Most common obscured causes of secondary HTN should be excluded prior to diagnosing resistant HTN. They are:
      1. Renal Parenchymal Disease
      2. Obstructive Sleep Apnea
      3. Primary Aldosteronism
      4. Renal Artery Stenosis
      5. Pheochromocytoma
      6. Cushing’s Syndrome
      7. Hyperthyroidism
      8. Coarctation of AO
  • Patient Selection Resistant Hypertension

    Diagnosing resistant hypertension can be difficult as physicians need to ensure that the sustained increase in blood pressure is not caused by inadequate adherence to medication, poor blood pressure measurement technique, “white-coat” hypertension, or a nonactive/ noncompliant lifestyle. The chart below will help you diagnose your patients for resistant hypertension and guide you if the patient is a candidate for renal denervation.

    renal denervation resistant-hypertension

  • Initiating Treatment for Hypertension

    renal denervation-treatment-hypertension

    Adapted from: J AM Coll Cardio. 2008; 52(22): 1749-157

  • References

    1. Calhoun DA, et al. Resistant hypertension: diagnosis, evaluation, and treatment: a scientific statement from the American Heart Association Professional Education Committee of the Council for High Blood Pressure Research. Circulation. 2008;117:e510-e526
    2. CDC. September 7, 2012: 61(35);703-706.
    3. Kearney PM, Whelton M, Reynolds K, et al. J Hypertens. 2004;22:11-19.
    4. Lawes CM, Vander Hoorn S, Rodgers A; for the International Society of Hypertension. Global burden of blood-pressure-related disease, 2001 Lancet 2008; 371: 1513–18
    5. Persell SD. Prevalence of resistant hypertension in United States, 2003-2008. Hypertension. 2011;57:1076-1080.
    6. Lewington S, Clarke R, Qizilbash N, Peto R, Collins R. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet. 2002;360:1903-1913.
    7. Singer G.M., Izhar M., Black H.R.; Goal-oriented hypertension management: translating clinical trials to practice. Hypertension. 40 2002:40:464-469.
    8. Sarafidis, P., Bakris, G. George. Resistant Hypertension: An Overview of Evaluation and Treatment. JACC. 2008;52(22): 1749–57
  • Disclaimer: This site is meant for educational purposes only, no medical advice is given or implied. Renal denervation is still an experimental treatment in many parts of the world, including the United States.