Although congestion is the primary cause of heart failure (HF) symptoms, its mechanism is poorly understood. The authors’ pathway and differential expression investigations aim to discover biological processes and biomarkers linked with congestion in HF. In the BIOSTAT-CHF study, 1,245 patients with newly diagnosed or worsening HF were given a congestion score, which included their jugular venous pressure, orthopnea, and the amount of peripheral edema they had. Patients who scored in the lowest (n=408) or highest (n=142) congestion categories were classified as not congested and highly congested, respectively. In this study, researchers evaluated the plasma concentrations of 363 distinct proteins between non-congested and severely congested individuals using the Olink Proteomics Multiplex CVD-II, CVD-III, Immune Response, and Oncology II panels. Independent validation in a population of 1,342 patients with HF confirmed the results (436 non-congested and 232 severely congested). Comparing individuals with congestion to those without, they found that 107 of 363 proteins were up-regulated and 6 were down-regulated. The proteins most significantly up-regulated were FGF-23, FGF-21, CA-125, soluble ST2, GDF-15, FABP4, IL-6, and BNP (fold change [FC] >1.30, false discovery rate [FDR], P<0.05). The proteins with the largest fold changes away from their averages were KITLG, EGF, and PON3 (FC<-1.30, FDR P<0.05). Inflammation, endothelial activation, and mechanical stimulation response were 3 of the most important pathways involved in congestion. Similar results were obtained from the validation cohort. It has been found that inflammation, endothelial activation, and mechanical stress are the primary causes of severe congestion in HF. The significance of these pathways in the development and worsening of congestion has yet to be determined. As these markers are further studied, they may one day aid with congestion diagnosis and tracking.