Investigations of Laser-Assisted Renal Denervation for Treatment of Resistant Hypertension

Background and ObjectivesRenal denervation (RDN) is an emerging surgical treatment for resistant hypertension. However, the current RDN using radiofrequency can cause undesirable thermal damage to the medial and luminal layers due to direct contact between the arterial lumen and energy source. The aim of this study is to evaluate the feasibility of the new laser-assisted RDN by exploring the potential treatment conditions.MethodsFor ex vivo testing, six different treatment conditions (10 and 20 W applied for delivery of 300, 450, and 600 J) were tested on the porcine liver and renal artery (RA) by using a continuous wave 1064 nm laser wavelength. The ablated area in the liver tissue was measured to estimate the extent of the coagulated area. Histological evaluation was performed on the treated RA tissues to confirm the extent of thermal nerve damage.ResultsThe ablated depth, length, and area in the liver tissue increased with laser power and total energy. According to the histological results, 20 W groups yielded more significant damage to the RA nerves than 10 W groups at the total energy of 300 J (0.0 +/- 0.0 mm for 10 W vs. 2.9 +/- 1.0 mm for 20 W), 450 J (1.9 +/- 0.6 mm for 10 W vs. 6.8 +/- 1.5 mm for 20 W), and 600 J (2.9 +/- 0.4 mm for 10 W vs. 7.3 +/- 0.8 mm for 20 W). The treated RA exhibited insignificant medial injury in depth (medial thinning <= 25%), and no difference in the medial thinning was found among the six groups (p = 0.4).ConclusionThe current study demonstrated that the 1064 nm laser at 20 W with delivery of 450 J could effectively damage the RA nerves with no or minimal injury to the surrounding tissue. The proposed laser-assisted RDN may enhance physiological effects with insignificant complications in in vivo situations. Further in vivo studies will be conducted to validate the current findings by evaluating the extent of blood pressure reduction and norepinephrine changes after the laser-assisted RDN on a large animal model.