317stimulating nociceptive afferent SNS. There is also a case report describing the
ADPKD patient in whom RDN leads to immediate resolution of 5-year chronic
flank pain.
There are some limitations of the RDN use in CKD patients. In some patients
with advanced CKD, atrophic renal arteries are characterized by too low diameter
to perform RDN. Also the measures to prevent contrast media nephrotoxicity
(mainly proper hydration) should be strictly applied before RDN in this group of
patients. Alternatively carbon dioxide as contrast agent might be used [ 16 ].
Promising results from small clinical studies (presented in Table 19.2) and case
reports may suggest that in CKD patients, RDN demonstrates nephroprotective
effects. However the role of RDN in the long-term treatment of these patients needs
to be confirmed by further clinical studies.
Baroreflex Activation Therapy
Another method of invasive nonpharmacological antihypertensive treatment, based
mainly on SNS activity reduction, is BAT.
Baroreceptors participate in baroreceptor reflex, which is one of the crucial
homeostatic mechanisms of maintenance the adequate blood pressure. Baroreceptors
are mechanoreceptors located in aortic arch, carotid sinuses, and carotid arteries.
Afferent nerves run from carotid sinus within glossopharyngeal nerve, and afferent
nerves from aortic arch run along with the vagus nerve. Both abovementioned
nerves terminate in nucleus of the tractus solitarius localized in the medulla oblon-
gata. Efferent fibers are the part of both sympathetic and parasympathetic nervous
system. Baroreceptors are activated by stretch of the vessel wall. Pressure induces
excitation and generates signals transmitted to the central nervous system. Due to
blood pressure increase, the further distension of the carotid sinuses and aortic arch
is observed. The greater stretch increases baroreceptor signalization. With the baro-
receptor activation, SNS is inhibited, and the parasympathetic nervous system is
activated. Sympathetic restrain is associated with reduction of peripheral vascular
resistance, while parasympathetic activation results in depression of the heart rate
and contractility. Both actions result in blood pressure decrease.
Clinical studies have shown that baroreflex sensitivity is lower in the elderly
subjects and hypertensive patients as well as CKD patients. Impaired baroreflex
control of HR is directly correlated with the severity of CKD and is an independent
risk factor of sudden cardiac death in people with CKD.
The first study concerning the effect of the baroreceptor stimulation on blood
pressure was done in 1965. Bilgutay and Lillehei used implantable device attached
to the carotid sinus in hypertensive dogs. The baroreceptors stimulation resulted in
blood pressure decrease. Subsequently these authors used this technique in two
hypertensive patients. It also resulted with the significant blood pressure reduction.
More recently experimental studies confirmed these early observations. It was
found that bilateral electric activation of carotid baroreflex in dogs lowered mean
19 Devices for Neural Modulation (Renal Denervation, Barostimulation)