Epicardio

Epicardio, or epicardium, is the outermost layer of the heart wall. It forms the visceral layer of the serous pericardium, enveloping the myocardium and lining the coronary grooves. In life it slides against the parietal pericardium, and the pericardial fluid between the layers reduces friction during cardiac motion.

Anatomy and tissue composition: The epicardium consists of a thin sheet of mesothelial cells supported by connective tissue. In many individuals, especially adults, it contains a variable amount of adipose tissue, notably along the coronary sulci. The subepicardial space houses the coronary arteries and veins and autonomic nerves that supply and regulate the myocardium. The epicardium also contributes to the production of serous fluid that lubricates the heart within the pericardial cavity and participates in paracrine signaling affecting cardiac tissue.

Development: Embryologically, epicardial cells originate from the proepicardial organ and spread over the developing heart. They invade the myocardium and differentiate to contribute to the coronary vasculature and to components of the heart’s connective tissue. In adulthood, the epicardium remains a source of signaling and repair factors that influence myocardial biology and healing after injury.

Clinical relevance: Isolated epicardial inflammation is uncommon; epicarditis is rare, with pericarditis more frequently diagnosed. Epicardial fat thickness is studied as a marker in obesity and cardiovascular risk. During cardiac surgery, the epicardial surface is often accessed for procedures such as coronary artery bypass grafting, and injury to the epicardium can impact healing and vascular remodeling.