Increasing electrical nerve stimulation current from 5 mA to 10 mA after renal artery ablation increased systolic blood pressure augmentation from 1.8% to 6.8% in middle renal artery segments.
Does higher current strength (10 mA vs 5 mA) affect the magnitude of ENS-induced blood pressure augmentation after renal artery radiofrequency ablation in beagles?
Higher current strength during electrical nerve stimulation after renal artery ablation captures deeper unablated nerves, causing blood pressure augmentation and highlighting the need for standardized stimulation protocols to assess ablation endpoints.
Absolute Event Rate: 6.8% vs 1.8%
Abstract Background Electrical nerve stimulation (ENS)-guided renal artery radiofrequency (RF) ablation is a therapeutic option for drug therapy-resistant hypertension but has reported inconsistent outcomes in several studies. Since blood pressure (BP) augmentation by ENS may be different depending on the stimulus strength, ENS may have a limitation in identifying the reasonable endpoints of RF applications, although this technique can be useful to determine the target ablation sites. Purpose Experimental study (approved by our Institutional Review Board) using beagles was performed to clarify how the current strength affects the magnitude of ENS-induced BP augmentation after renal artery RF ablation. Methods Under fluoroscopic guidance, a deflectable decapolar electrode catheter was placed into either side of the renal artery via the left femoral artery. Before RF ablation, ENS (20 Hz frequency, 2-ms width, 60-seconds duration) with 5 mA was applied from the middle and distal segments of the 7 renal arteries (m-RA and d-RA) in the 4 beagles using a decapolar electrode catheter. After RF ablation at m-RA segments using an open irrigation catheter (10-W, 120-seconds), both 5 mA and 10 mA ENS were attempted from m-RA and d-RA segments, and differences in the ENS in the BP augmentation between 5 mA and 10 mA ENS were assessed. Results Before ablation: 5 mA ENS at m-RA and d-RA segments increased the BP, from 144±14/80±13 to 176±19/106±13 mmHg and from 141±16/81±15 to 185±20/116±18 mmHg, respectively. Systolic BP augmentation in d-RA segments was 32±15% and that in m-RA segments was 23±12%. After ablation: Renal artery RF ablation was accomplished without any acute complications. BP augmentation by 5 mA ENS had almost disappeared not only at the ablated m-RA segments but also at the d-RA segments; from 139±13/81±9 to 142±13/82±10 mmHg and from 141±15/81±11 to 145±13/86±8 mmHg, respectively. However, the higher 10 mA ENS increased the BP, from 137±16/78±15 to 146±15/87±13 mmHg in m-RA segments and from 140±8/79±6 to 152±14/92±10 mmHg in d-RA segments, respectively. As the current strength increased (from 5 to 10 mA), ENS-induced systolic BP augmentation increased from 1.8±3.2 to 6.8±7.2% in m-RA segments and from 3.6±6.0 to 8.3±9.1% in d-RA segments after RF ablation. Furthermore, RA segments showing more than 10 mmHg BP augmentation increased from 3/14 to 6/14 segments of either m-RA or d-RA. Discussion: Wide area capture by higher current strength ENS may stimulate those renal autonomic nerves located farther from the inner vascular wall of the renal artery, where effective lesions are unable to be created by RF ablation from inside the renal artery. This may be a reason why varying long-term results are reported in ENS-guided renal artery ablation. Conclusions Identification of appropriate ENS modes would be required to determine the reasonable endpoints of the operation and to predict long-term effects of renal artery ablation.
Chinushi et al. (Sat,) conducted a other in Hypertension (animal model) (n=4). 10 mA electrical nerve stimulation vs. 5 mA electrical nerve stimulation was evaluated on Systolic blood pressure augmentation in middle renal artery segments after RF ablation. Increasing electrical nerve stimulation current from 5 mA to 10 mA after renal artery ablation increased systolic blood pressure augmentation from 1.8% to 6.8% in middle renal artery segments.