Resistant Hypertension in Chronic Kidney Disease

311

with the proximal and middle segments and the mean distance from renal artery
lumen to nerve location is the lowest in the distal segments. Additionally the higher
total number of nerves in ventral region than in dorsal part of renal arteries was
shown. Nevertheless, on average, more than 75% of nerves are placed within a dis-
tance of 4.3 mm from renal artery lumen. This anatomy of renal nerves (i.e., vicinity
to renal arteries lumens) allowed to develop procedures of selective renal SNS
nerve damages by applying different stimuli through devices placed in renal arter-
ies, i.e., RDN.
Unfortunately currently, there are no clinically useful methods to precisely define
the anatomical localization of renal SNS nerves in particular patient. The preferred
segment of renal artery for the effective intervention is also unknown. It is unclear
whether it is better to ablate renal SNS nerves in proximal segment (where bigger
but fewer nerves are localized) or in distal segment (where smaller but more nerves
are present).
Percutaneous, intravascular catheter-based procedures, described below, aimed
to damage selectively renal nerves are still under development and investigations
(Table 19.1). The agents used to damage renal arteries in experimental or clinical
studies are radiofrequency energy (RF), ultrasound energy, and pharmacological
ones (Table 19.1).
RF ablation is so far the most developed method of RDN.  The procedure
using RF generator enables to injury renal sympathetic nerves with controlled heat
(45–70 °C). Systems using single electrode (e.g., Symplicity) need several applica-
tion of energy in every renal artery. Multielectrode systems (like EnligHTN) are
composed of a several-arm tip and deliver energy in a few positions at the same
time. It results in shorter duration of the treatment and reduces the volume of con-
trast medium used in the procedure. The Celsius ThermoCool RFA catheter system
uses a saline- irrigated catheter for RDN. Saline irrigation was used in this catheter

Table 19.1 Methods of endovascular renal nerve ablation

Method of renal

denervation Product name Type of catheter Current experience

Radiofrequency

ablation (RFA)

Symplicity RFA

catheter

Single-electrode RFA

catheter

Randomized clinical

study

EnligHTN RFA

catheter

Multielectrode

catheter

Nonrandomized

clinical study

ThermoCool RFA Irrigated RFA

catheter

Nonrandomized

clinical study

Ultrasonic ablation PARADISE

ultrasonic catheter

Ultrasonic balloon

catheter

Nonrandomized

clinical study

TIVUS ultrasonic

catheter

Ultrasonic

autoregulating

balloon catheter

Proof-of-concept

clinical study

Pharmacological

ablation

Bullfrog

microinfusion

catheter

Microneedle- equipped

balloon catheter

Experimental study

R FA radiofrequency ablation

19 Devices for Neural Modulation (Renal Denervation, Barostimulation)