Epikardiale

Epikardiale, or epicardium in English, refers to the outermost layer of the heart. It is the visceral layer of the serous pericardium that directly covers the myocardium and forms part of the pericardial sac. The epicardial surface is a two-layer structure: a thin mesothelial cell layer and a subepicardial connective tissue layer, which often contains adipose tissue, particularly around the coronary grooves.

Anatomy and relationships

The epicardium is continuous with the parietal layer of the serous pericardium at the great vessels and envelops the coronary arteries and veins within the subepicardial fat. In prominent regions, notably along the atrioventricular and interventricular grooves, the epicardial fat can be substantial. Nerve fibers run within the epicardial and subepicardial layers, contributing to cardiac innervation.

Embryology

During heart development, cells from the proepicardium migrate to the heart surface to form the epicardium. Through epithelial-to-mesenchymal transition, epicardial cells contribute to the coronary smooth muscle, fibroblasts, and parts of the extracellular matrix, supporting the formation of the coronary vasculature.

Function and clinical relevance

The epicardium serves as a protective covering and a conduit for coronary vessels and nerves, playing a role in heart development and regeneration. Epicardial adipose tissue is metabolically active and may influence cardiovascular risk through inflammatory mediators. Clinically, the epicardial surface is involved in procedures such as epicardial ablation for certain arrhythmias, which requires careful consideration of nearby coronary arteries and the phrenic nerve. Inflammation of the pericardial layers, including the epicardium, manifests as pericarditis, with associated chest pain and fluid accumulation in the pericardial cavity.

Terminology

Epikardiale is the term in several languages for the epicardium, the visceral layer of the serous pericardium.