Catheter-based renal denervation in hypertension: heading for new shores
Autonomic imbalance, the loss of equilibrium between the sympathetic and parasympathetic nervous systems, is thought to play an important role in the pathophysiology of hypertension . The activation of renal sympathetic fibers, which reside throughout the kidney and abound in the hypertensive state, leads to an increased and excessive secretion of renin, increased sodium reabsorption in the proximal tubule, and decreased renal perfusion . In the not so distant past, these observations seemed to support and promote the use of surgical sympathectomy in patients with severe hypertension, including individuals with end-organ damage, and indeed was associated with significant reduction in blood pressure (BP) accompanied by reduced mortality . Surgical approaches requiring major operative approach became a method of last resort and then a neglected relic of the past until catheter-based approaches promised minimally invasive targeting of renal nerves. An ablation catheter introduced through the femoral or radial artery can be advanced into the renal arteries under fluoroscopic guidance, in which radiofrequency or ultrasound energy can be deployed to ablate the sympathetic nerves . Alternative approaches use chemical denervation by injection of alcohol or other neurotoxic agents in the adventitia of the renal arteries. Although minimal invasiveness was proved and early data seemed promising, unambiguous BP lowering with noninvasive renal denervation (RDN) remains elusive, especially in light of the well executed trials .