14 - Exploring the Correlation Between Catecholaminergic Activity in the Cervical Vagus Nerve and Signs of Cardiac Remodeling: Implication for Vagus Nerve Stimulation Therapy

Poster Board Number: 14
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Odd poster #s – first hour
Even poster #s – second hour

Co-authors:

Aadhya Subhash - Biology and Environmental Health - Missouri Southern State University; Dhvani Patel - Biology and Environmental Health - Missouri Southern State University; Shelby Kuhnert - Biology and Environmental Health - Missouri Southern State University; Mary Kilmer - Missouri Southern State University; Alla Barry - Biology and Environmental Health - Missouri Southern State University

Abstract Body : INTRODUCTION. The process of cardiac remodeling (CR), triggered by heightened sympathetic outflow, involves changes in heart geometry and accumulation of connective tissue (CT) within the myocardium. These alterations lead to impaired ventricular functions and influence the progression of heart failure. Simultaneously, parasympathetic outflow, conveyed through the cardiac branches of the Vagus Nerve (VN), exerts cardioprotective effects, reducing the risk of CR. Recent studies revealed the presence of catecholaminergic fibers (CF) in the cervical VN. These newly discovered CF, likely postganglionic sympathetic, challenge established understanding of the nerve's composition and function. Their existence raises concerns of impacting the cardioprotective effects attributed to the parasympathetic nervous system. The aim of our study was to explore the correlation between the quantity of CF within the cervical VN and indicators of CR.

METHODS. Cervical VN samples were obtained for histological processing from 10 formalin-preserved adult human cadavers (male n=5, female n=5). All sections were prepared using Luxol fast blue and anti-Tyrosine Hydroxylase (TH) antibody. Superior Cervical Ganglia were examined for TH-reactivity to confirm the quality of TH detection. Heart dimensions and wall thickness were measured before collecting myocardium for histological processing with trichrome to detect the presence of CT. TH+ areas and CT were measured on photographed slides using ImageJ. Data were analyzed using PAST 4.11.

RESULTS. The analysis revealed the presence of TH+ fibers bilaterally or unilaterally in 9 out of 10 examined donors, with varying prevalence ranging from 0% to 15%. Upon conducting linear regression analysis, no statistically significant correlation was observed between the quantity of vagal CF and indicators of CR. However, a trend towards significance emerged in the relationship between the quantity of CF and abnormal thickness observed in the left ventricular wall and interventricular septum (p=0.056).

CONCLUSION. Our study reinforced the understanding of the persistent presence of CF within the cervical VN. The findings indicated a lack of correlation between the quantity of TH+ fibers and extent of CR. However, several trends for statistical significance were detected. Thus, further investigations with an expanded sample size are warranted to enhance the robustness of our conclusions.

SIGNIFICANCE. Vagus Nerve Stimulation (VNS) has shown promise in triggering reverse CR in patients with heart failure. However, nearly 25% of them fail to derive therapeutic benefits or encounter adverse reactions. Vagal CF might disrupt the expected positive and cardioprotective effects of VNS therapy, potentially contributing to adverse responses.