Renal Nerve Ablation for Resistant Hypertension

Abstract

Sympathetic renal denervation, or renal nerve ablation (RNA), has become the new buzz word in hypertension and interventional cardiology. Recent advances in catheter-based approaches have allowed sympathetic fiber interruption through transvascular techniques that are minimally invasive and can be delivered expeditiously and safely. Radiofrequency (RF) energy sources are currently the preferred modalities, but other sources of energy, such as cryoablation, microwave, high-intensity focus ultrasound, and local neurotoxic agent infusion, are under intense investigation. Results thus far have been encouraging and offer promise for the future. The role of the sympathetic nervous system (SNS) in the development of resistant hypertension and cardiovascular disease has long been known, and a great deal of work has been done through the years trying to explore potential interventions to interrupt the sympathetic influence on systemic vasculature and target organs. In this article we attempt an overview of time-dependent interventions on the SNS and examine approaches used in humans and in the many experimental models that offer a better understanding of the role of sympathetic activity in cardiovascular disease. Naturally we focus on methods and techniques addressing sympathetic renal denervation in patients with drug-resistant hypertension, examine the current state of the art, and attempt a look into the future. In 1889, after meticulous experiments on dogs, Bradford1 reported that stimulation of dorsal and splanchnic nerves causes changes in blood pressure (BP) and kidney size measured by plethysmography. Whether BP increased or decreased depended on the anatomic area stimulated, as well as the electric impulse frequency, but outcomes were consistent and reproducible. Neurosurgical treatment of hypertension was independently suggested by researchers in 1923.2 Adson, however, was the first to performed surgical sympathectomy for the treatment of malignant hypertension in 1925.3 During the following years and in the 1930s, Peet in Ann Arbor, Page and …