Assessment of morphological criteria for the efficiency of radiofrequency circumferential denervation of the pulmonary artery in the experiment (animals, pigs)

Abstract

The aim of the study. To assess the influence of radiofrequency circumferential exposure modes on the morphological parameters of the pulmonary artery tissues in animal experiment (pigs).Material and methods. In the experiments, we used outbred pigs divided into 3 groups (4 animals in each). The first experimental group included 188 histological samples of the pulmonary arteries (PA) after radiofrequency circumferential exposure on the PA using an ablator clamp. Two lines of exposure on the PA and two lines of exposure on each PA mouth were performed. Ablation was performed until the target level of tissue impedance between the ablator branches corresponding to the values at transmural damage was reached. The second experimental group included 162 histological samples of the PA after circumferential denervation of pulmonary trunk and both PA mouths. Ablation was completed upon reaching 50 % impedance level relative to the impedance values at transmural damage. The third group (control) included 55 histological samples of PA without radiofrequency exposure. The material obtained was studied using light microscopy, hematoxylin and eosin and van Gieson’s staining, and also by impregnation with silver salts according to S. Ramón y Cajal.Conclusions. Morphological criteria for irreversible destruction of nerve fibers and ganglia of the pulmonary trunk adventitial layer and for PA bifurcation were obtained when using two studied ablation modes. Circumferential PA denervation using subthreshold power of radiofrequency exposure made it possible to avoid irreversible damage to the nerve endings and ganglia of the PA intimal layer and thus to preserve physiological neuroreflectory regulation of the PA and the entire pulmonary circulation. Turning off the cascade of pathological reflexes eliminates the factor of the progression of pulmonary hypertension associated with an increase in peripheral resistance of the pulmonary arterioles precapillary link.

Technical Features of the Experimental Target Device for Denervation of the Pulmonary Arteries

“…The clamping structure of the device, as well as its close analogue, is designed for stable fixation of the position and uniform compression of the vessel tissues until the walls of the PA are in full contact with each other. At the same time, the following zones of the PA vascular wall located between the branches of the ablator clamp can be clearly distinguished: the anterior and posterior walls of the PA, as well as the places of folds, which we designated as the "marginal zones" of the wall of the occluded vessel (Figure 2) [9].…”