The endocardium is the innermost layer of the heart wall, consisting of a thin layer of endothelial cells and connective tissue that lines all four heart chambers and covers the heart valves. On echocardiography, the endocardial surface is used as the reference boundary when tracing ventricular volumes and calculating ejection fraction. A clearly defined endocardial border is essential for accurate measurements, and contrast agents can be used to improve endocardial visualization when image quality is suboptimal. Diseases affecting the endocardium include endocarditis, endocardial fibroelastosis in infants, and Loeffler endocarditis, in which the endocardium becomes thickened and stiff.
Sonography Term