EAT expansion in obesity and CAD exerts detrimental effects via 3 overarching mechanisms: direct paracrine/vasocrine diffusion of harmful mediators into the myocardium and coronaries, local and systemic inflammatory crosstalk, and mechanical burden on the heart. Human histological and imaging studies have shown that EAT expands and becomes inflamed in obesity and CAD [
124]. Its volume increases and it becomes infiltrated by proinflammatory immune cells, especially M1 macrophages. Harmful mediators including excess FFAs and ROS diffuse directly into the adjacent myocardium and coronary arteries due to the absence of a fascial barrier, promoting endothelial dysfunction, oxidative stress, and atherosclerotic plaque instability [
125]. Excessive FFAs from EAT also contribute to myocardial lipotoxicity, insulin resistance, and fibrotic remodeling [
126]. Moreover, increased EAT imposes a mechanical burden on the heart, exacerbating ventricular hypertrophy and diastolic impairment [
127]. The inflammatory crosstalk between EAT and the adjacent myocardium plays a vital role in the development and progression of heart failure (HF), occurring through multiple pathways that create a vicious cycle of myocardial dysfunction and metabolic derangement, thereby exacerbating HF progression. Dysfunctional EAT secretes a plethora of proinflammatory adipokines and cytokines that directly infiltrate the cardiac muscle through paracrine and vasocrine pathways. In patients with HF with preserved ejection fraction, EAT exhibits markedly elevated expression levels of proinflammatory cytokines, including IL-1β, IL-6, and TNF-α, demonstrating a strong correlation with echocardiographic indices of diastolic dysfunction [
128]. In response to this inflammatory milieu, mouse myocardial tissue up-regulates chemokines such as MCP-1, which facilitates the recruitment of macrophages into EAT, thereby establishing a self-perpetuating inflammatory feedback loop that exacerbates myocardial pathology [
129]. In cardiomyocytes, TNF-α impairs calcium handling and reduces contractility via activation of the NF-κB pathway [
130], while IL-1β facilitates cardiomyocyte hypertrophy and apoptosis via activation of the p38 mitogen-activated protein kinase pathway, concurrently contributing to endothelial dysfunction within the coronary microvasculature [
131]. Notably, EAT from patients with HF exhibits dramatic up-regulation of inflammasome components, particularly NLRP3, which enhances the processing and release of IL-1β [
132]. This localized inflammatory environment is further intensified by a decrease in the secretion of protective adipokines such as adiponectin, which typically exert anti-inflammatory and cardioprotective effects [
133]. The inflammatory interplay extends beyond cytokines to encompass extracellular vesicles. Exosomes derived from EAT in HF patients are enriched with specific microRNAs (such as miR-27a, miR-130a, and miR-200c) that facilitate myocardial fibrosis by activating TGF-β signaling pathways in cardiac fibroblasts [
134]. These exosomes also carry dysfunctional mitochondrial DNA that activates Toll-like receptor 9 (TLR9)-mediated inflammatory responses in mouse cardiomyocytes [
135]. In coronary atherosclerosis, EAT-derived exosomal miRNAs mediate intercellular communication with coronary vasculature to regulate plaque formation [
136]. For example, EAT-derived miR-92a-3p improves the myocardial redox state by modulating Wnt5a signaling and is related to improved clinical outcomes [
137]. Clinically, a study on CAD patients identified 385 differentially expressed proteins in EAT compared to non-CAD controls, with enrichment in pathways related to lipid metabolism, inflammation, and oxidative stress, providing a human proteomic landscape of EAT dysfunction [
138]. These changes contribute to myocardial inflammation, fibrosis, and ischemia, linking EAT dysfunction to adverse cardiac outcomes [
139]. In summary, converging evidence from human studies and animal models positions dysfunctional EAT as a central endocrine and inflammatory organ that exacerbates cardiac pathology through multifaceted crosstalk, making it a compelling target for cardiometabolic intervention.