Quantitative immunohistochemical evaluation of the efficacy of radiofrequency pulmonary artery denervation

Objective. To perform a morphological evaluation of the efficacy of radiofrequency pulmonary artery denervation using immunohistochemical staining of ganglionic nerve plexuses and autonomic nerve fibers with antibodies against S-100 protein. Materials and Methods. Thirty pulmonary trunks from individuals who died of extracardiac pathology, aged 31 to 65 years (autopsy material), were studied. Five pulmonary trunks served as controls, while 25 were treated with radiofrequency pulmonary artery denervation (RFA-PA) using an experimental generator (440 kHz, power 10 W). Paraffin sections of 4 μm thickness were stained on a Leica Bond MAX immunostainer with polyclonal antibodies against S-100 protein. The relative area of nerve fibers (Srel.) was used as the statistical parameter. Results. In control specimens, pulmonary nerve fibers after S-100 protein staining were predominantly detected along the left lateral edge of the pulmonary trunk: median Srel.=5.72% (95% CI 4.27–8.95). A small number of fine nerve fibers were found in the anterior and posterior walls of the pulmonary trunk: Srel.=0.99% (95% CI 0.48–0.93), p<0.0001. In sections of pulmonary trunks subjected to RFA-PA, nerve fibers did not stain for S-100 protein, indicating thermal coagulation of proteins with loss of specific three-dimensional structure and antigenic properties. Conclusion. Quantitative immunohistochemical evaluation using antibodies against S-100 protein is an objective method for verifying irreversible thermal damage to autonomic nerve fibers of the pulmonary artery and allows assessment of radiofrequency denervation efficacy. This method can be used in clinical and experimental work to evaluate ablation efficacy in both autopsy and biopsy material.