Majority of patients with Hypertension and no identifiable secondary causes have demonstrated activated sympathetic nervous system and increased sympathetic outflow.1 Because of lack of therapeutic options sympathectomy for the treatment of malignant hypertension (terminology then abandoned) appears to have taken place for the first time in Germany as early as 1923(9). During late 1930’s first report of non-selective thoracolumbar splanchnincectomy (from the 8th to the 12th dorsal root ganglion) from the United Stated was published to treat hypertension. Clinical trial data demonstrated 5-year mortality rates of those treated surgically, n=1266, of 19%.1 In comparison patients that did not undergo the surgery, n=467, the 5-year mortality rate was 54%. Some successfully operated patients had lower BP that extended up to 10 years. By 1960s there were multiple reports proving the effectiveness of sympathectomy in treatment of malignant HTN. At the same time every report suggested that the operating technique required prolonged hospitalization and long recovery period. The procedure had very serious procedural risks and some adverse events included orthostatic hypotension, orthostatic tachycardia, palpitations, breathlessness, anhidrosis, cold hands, intestinal disturbances, loss of ejaculation, sexual dysfunction, thoracic duct injuries, and atelectasis.1 Multiple reports in 1950s evaluated effect of ganglion-blocking agent in the treatment of malignant hypertension. Harrington et al. reported improved life expectancy with the treatment of ganglion blocking treatment.2
Renal Denervation Today
Among the different approaches the one that has shown exciting clinical trial results is catheter-based renal denervation targeting only the renal nerves in the adventitia of the arterial wall, thereby reducing the brain-kidney crosstalk and systolic blood pressure.4 SymplicityTM pioneered the radiofrequency based renal denervation system which demonstrated outstanding results in reducing systolic blood pressure in patients with resistant hypertension. There have been several key players that are emerging with both ultrasound and radiofrequency based electrodes for RDN, for which some analysts predict that the market value will hit $2 billion worldwide.
Ablating renal sympathetic nerves to treat resistant hypertention
Three forms of energy are being studied for trans-catheter based renal denervation:
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Recently a systemic review/meta-analysis study evaluating the safety and efficacy of RDN for resistant HTN was published.4 A review of 2 randomized control trial, one case control study and 9 observation studies showed mean reductions of SBP and DBP of 28.9 mm Hg and –11.0 mm Hg, respectively,compared with medically treated patients (for both P < 0.0001). Five different catheters were reviewed and showed no difference in the effect of RDN. Reported procedural complications included 1 renal artery dissection and 4 femoral pseudoaneurysms.4 While trans-arterial renal denervation has been the major focus of study, trans-ureteral renal denervation, non-invasive renal denervation, gamma knife and nanotechnology are some of the other ideas in the pipeline focusing on the same target.
Renal Denervation Devices in the Marketplace
- Doumas M, MDA C, Faelis C, et al. Renal Sympathetic Denervation and Systemic Hypertension. Am J Cardiol. 2010;105:570–576.
- Harington M, Kincaid-Smith P, McMichael J. Results of treatment in malignant hypertension: a seven-year experience in 94 cases. British Medical Journal. 1959;2(5158):969–980.
- Bunte, M; Oliveira E; Shishehbor, M. Endovascular Treatment of Resistant and Uncontrolled Hypertension. J Am Coll Cardiol Intv. 2012;():. doi:10.1016/j.jcin.2012.09.005
- Davis MI, Filion KB, Zhang D, et al. Effectiveness of Renal Denervation Therapy for Resistant Hypertension: a systematic review and meta-analysis. J Am Coll Cardiol. 2013;62(3):231-241.