Abstract P203: Insights To Lesion Formation For Percutaneous Renal Denervation: Human And Porcine Histological Analyses

Abstract

Background: The safety and efficacy of radiofrequency (RF) renal denervation (RDN) have been demonstrated in multiple randomized trials. We performed histological analyses in a swine model and human cadavers to investigate RF lesion geometry, morphology and location in the context of local anatomic structures and describe their impact on procedural outcomes. Methods: The Symplicity Spyral catheter was used to perform RDN in 164 renal arteries from healthy swine terminated at 7 days post-treatment. Lesion characteristics were determined by semi-quantitative histology. Renal nerve functionality was measured by quantitative immunohistochemistry and correlated to renal norepinephrine. In addition, we investigated the retroperitoneal space in 10 human cadavers to determine the relative location of extravascular tissues. Results: In the swine model, RF lesions developed exclusively in the perivascular adipose tissue which contains the renal nerves. Lesions were irregularly shaped due to inherent sparing of surrounding perfused structures, such as veins and lymph nodes. Maximum depth of the irregularly shaped RF lesions was 6.8±2.5 mm, and mean depth was 3.9±2.4 mm. Renal norepinephrine levels were lowest when >80% of renal nerves were ablated ( Figure ). Reendothelialization of the lesion area was >99% within 7 days. In humans, only 0.3% of renal nerves were localized on the opposite side of the renal veins. Conclusion: Patterns of RF RDN are uniquely influenced by electrical and thermal conduction properties of tissues surrounding the renal arteries. Maximal reduction of renal norepinephrine content requires ablation of at least 80% of the renal nerves.