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A novel, catheter-based technique is looking promising for the treatment of refractory hypertension. The autonomic nervous system is known to supply sympathetic nerve fibres to the kidneys. Hyperactivity of these renal sympathetic nerves is associated with the development of hypertension and its progression, as well as chronic kidney disease (CKD) and heart failure. While surgical procedures to eliminate the sympathetic nerves have been considered over the past 50 or more years, the procedure is very invasive and no longer routinely performed.
"Keyhole" renal sympathectomy is now possible, using a steerable femoral 6F catheter with an RF energy electrode tip, by delivering a series of 2 minute ablations to the renal artery, causing renal denervation (RDN) and blood pressure reduction.
An initial proof of principle study was reported in The Lancet (Krum H et al. Lancet 2009;373:1275–81) by Dr Henry Krum (Monash University, Melbourne, Australia) and co-investigators who, using the newly developed Symplicity® catheter system, performed RDN in 45 patients with resistant hypertension (systolic blood pressure [SBP] ≥160 mmHg on three antihypertensive agents); the procedure lasting a median of 38 minutes. The primary end points were office blood pressure (BP) and safety data at one, three, six, nine and 12 months, and patient's renal angiography and magnetic resonance angiography during follow-up.
BP was significantly reduced by, -14/-10, -21/-10, -22/-11, -24/-11 and -27/-17 mmHg at these pre-specified time points compared with five non-treated patients who had elevations in BP. Renal function (estimated glomerular filtration rate [GFR] and creatinine) was sustained and there were no renovascular complications. One intraprocedural renal artery dissection occurred before the ablation without sequelae.
The same team reported the two-year 'durability' of BP reduction among the cohort after RDN, during the European Society of Hypertension Congress. In all, 117 patients were treated at 17 centres. BPs were reduced by -20/-11, -24/-10, -24/-12, -25/-12, -29/-17 and -33/-14 mmHg at, one, three, six, 12, 18 and 24 months respectively. One patient required renal artery stenting for a lesion present at baseline, otherwise there were no adverse late events.
Catheter-based RDN therefore appears to produce substantial reduction in BP sustained to at least two years and changes in eGFR "are better than the natural history reported in similar patients" say the authors. UK workers, are involved in further assessment of RDN as a treatment for resistant hypertension.
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