The Differences Between Catheter-based And Extravascular RDN
- DeepQure
- 22 hours ago
- 4 min read
Renal denervation (RDN) is the ablation of nerves that run along the renal arteries. The procedure reduces the sympathetic nervous system’s activity to lower a patient’s blood pressure. As an emerging treatment for hypertension, RDN is currently an adjunct for more clinically established options such as antihypertensive drugs. There is, however, potential for it to become the first-line treatment for some patient segments, while still serving as a supplementary therapy for others.
RDN’s massive clinical potential has spurred the development of various approaches to the procedure. Medtronic’s Symplicity Spyral, for instance, uses a catheter that generates and delivers radiofrequency (RF) energy to ablate the renal nerves, while Recor Medical’s Paradise does so with ultrasound. Other devices are currently undergoing development and clinical validation. They range from RF- and ultrasound-based solutions to alternatives such as alcohol-mediated denervation, where dehydrated alcohol functions as the neurolytic agent.
Interestingly, all but one of the RDN technologies that are under development are catheter-based. The sole exception? DeepQure’s HyperQure system, which performs extravascular RDN through a laparoscopic approach. Although catheter-based and extravascular RDN are both minimally invasive procedures, they have fundamental differences that affect their respective efficacies.
Risk of vascular damage
As the renal nerves are located outside the renal arteries, catheter-based RDN solutions must perform ablation through the arterial wall – and risk damaging it. Medical device companies have developed various features to mitigate this. In some RDN systems, distal balloons are inflated with coolant to remove heat from the inner arterial wall as a protective measure. In others, blood flow through the renal artery is carefully maintained to achieve the same cooling effect.
The risk of vascular injuries isn’t binary. Instead, surgeons may need to balance patient safety against RDN efficacy, as more complete denervation will yield a greater reduction in blood pressure, but come with higher risks of artery damage. Such a trade-off may preclude patients with preexisting vascular conditions from undergoing RDN.
DeepQure’s solution is designed to reduce these issues entirely with its extravascular approach. As the HyperQure system reaches and ablates the renal nerves directly from the outside of the renal arteries, it aims to avoid the risk of vascular damage. This is particularly so for the arteries’ fragile endothelium layer, which lines the interior surface of blood vessels.
Completeness of nerve ablation
Vascular damage aside, catheter-based RDN systems also face efficacy limits due to variances in nerve distribution. "A 2014 study had previously revealed that the renal nerves are not evenly distributed at different locations in the human body," shared Dr Chang-Wook Jeong, co-founder and Chief Medical Officer of DeepQure.
“A few years later, I was part of a research project that looked into this more closely,” continued Dr Jeong. “We found that a significant percentage of renal nerve fibers are located further than the lesion depth created by conventional catheter-based RDN systems. The implication here is that such systems will not be able to ablate these nerves.”
The HyperQure system, in contrast, has a segmented electrode tip that wraps around the renal artery for direct, circumferential denervation. This approach is designed to enable complete ablation, regardless of the patient’s renal nerve distribution pattern. Complete ablation across patients isn’t just an improvement in terms of consistency. Rather, it may translates to a better clinical outcome through a greater reduction in blood pressure.
Anatomical suitability
Besides their unique nerve distribution patterns, patients also vary in terms of renal artery layout. The problems here are branched and accessory arteries – the former has the main renal artery branching into narrower ones, while the latter involves smaller “secondary” arteries that run parallel to the main vessel. Although these variations also carry renal nerves, they may be too small for catheters to enter to perform denervation.
Branched and accessory arteries are common: a 2020 study examined 314 patients and found that approximately half of them had multiple small renal arteries for both kidneys to, effectively, preclude catheter-based denervation. “Of course, the actual arterial size limits will differ between different RDN systems,” noted Dr Jeong. “But you can look at a particular system’s exclusion criteria to infer what these limits are.”
Neither branched nor accessory arteries have posed a problem for the HyperQure system though, as its electrode tip comes in three different sizes to target arteries with diameters from 2mm to 11mm. According to Dr Jeong, the system’s lower limit is a notable advantage: accessory arteries usually have diameters smaller than 3 mm, but the HyperQure system is designed to address most of them.
Evolving beyond catheter-based RDN
As clinical evidence for RDN continues to grow, the field will soon enter a pivotal phase of differentiation. Catheter-based systems have laid the foundation for RDN’s viability and safety, despite remaining constrained by anatomical and procedural limitations. On the other hand, an extravascular approach like HyperQure’s represents an evolution of a proven concept – one that seeks to address these constraints through direct, circumferential, and complete denervation.
HyperQure is currently undergoing clinical trials. As these ongoing studies confirm its efficacy and safety profile, the system is on its way to redefining how RDN is performed, as well as the patient segments it is suitable for. In time, it may just be the system that could elevate renal denervation to become a mainstream treatment for hypertension.
