Electrical stimulation–based evaluation for functional modification of renal autonomic nerve activities induced by catheter ablation

Background Catheter ablation of the renal artery can be performed without apparent angiographic stenosis. This suggests that renal nerve function can be attenuated with minor structural damage to the renal artery. Objective To clarify this hypothesis, we examined the relationship between electrical nerve stimulation (ENS)–induced blood pressure (BP) response and severity of histological injury of the renal artery using an acute canine model of renal artery ablation. Methods An irrigation catheter was inserted into the renal arteries of 8 dogs, and radiofrequency current was delivered at 15, 20, or 25 W. ENS was applied to each artery before and after ablation. Results Before ablation, ENS increased the BP and heart rate from 145 ± 15/86 ± 13 to 189 ± 21/111 ± 19 mm Hg and from 116 ± 9 to 130 ± 6 beats/min, respectively. Heart rate variability indices and serum catecholamine levels were elevated concomitantly. After ablation, the ENS-induced increase in BP and heart rate were markedly attenuated after 15 W ablation and those were nearly completely inhibited after 20 or 25 W ablation. An increase in heart rate variability indices and serum catecholamine levels became insignificant regardless of the applied energy. Renal artery angiograms revealed stenotic lesions only after 25 W ablation procedures. Histological studies showed mild to moderate injury of the arterial wall and autonomic nerves caused by 20 and 25 W ablation procedures, whereas only minor changes caused by 15 W ablation. Conclusion Functional renal autonomic nerve ablation is potentially performable with the guidance of ENS.