Development of Microwave-Based Renal Denervation Catheter for Clinical Application

Renal Denervation (RDN) has been developed as a potential treatment for hypertension that is resistant to traditional antihypertensive medication. This technique involves the ablation of nerve fibers around the renal artery from inside the blood vessel, which is intended to suppress sympathetic nerve activity and result in an antihypertensive effect. Currently, clinical investigation is underway to evaluate the effectiveness of RDN in treating treatment-resistant hypertension. Although radio frequency (RF) ablation catheters are commonly used, their heating capacity is limited. Microwave catheters are being considered as another option for RDN. We aim to solve the technical challenges of applying microwave catheters to RDN. In this paper, we designed a catheter with a helix structure and a microwave (2.45GHz) antenna. The antenna is a coaxial slot antenna, the dimensions of which were determined by optimizing the reflection coefficient through simulation. The measured catheter reflection coefficient is -23.6dB using egg white and -32dB in the renal artery. The prototype catheter was evaluated by in vitro experiments to validate the simulation. The procedure performed successfully with in vivo experiments involving the ablation of porcine renal arteries. The pathological evaluation confirmed that a large area of the perivascular tissue was ablated (>5mm) in a single quadrant without significant damage to the renal artery. Our proposed device allows for control of the ablation position and produces deep nerve ablation without overheating the intima or surrounding blood, suggesting a highly capable new denervation catheter.