Medtronic Ardian Symplicity™ Renal Denervation Devices

Abstract

In April 2007, Dr. Henry Krum and colleagues successfully performed the first percutaneous renal sympathetic denervation (RDN) in a patient with severe treatment resistant hypertension (TRH). Two years later, they published the sentential Symplicity HTN-1 trial results, assessing the safety and blood pressure lowering effects of renal denervation in 53 THR patients through 12-month follow-up. This report simultaneously captured the interest of the nephrology, hypertension and interventional communities and refocused attention on the kidney as a sympathetic nervous system therapeutic target in the treatment of drug resistant severe hypertension. Subsequent to this report, a small-randomized crossover trial, Symplicity HTN-2, has provided additional insights into the effectiveness and safety of the Medtronic Ardian renal denervation devices and fostered its consideration as a viable therapy for TRH. Preliminary preclinical experience suggests that the most reliable morphological parameters reflecting successful renal denervation are the presence of axonal degeneration and the accompanying decline in renal parenchymal norepinephrine content. The technical procedural parameters (i.e., electrode diameter, temperature, impedance, wattage, number of ablation sites per artery and ablation duration) have been adopted from these surrogates defined in preclinical studies of normal swine renal arteries. This chapter will review the underlying biophysics of RF monopolar ablation, the experience with the Medtronic Ardian renal denervation catheter systems (Symplicity Arch™, Flex™ and Spyral™ Catheters (Table 7.1)) and their points of differentiation.