Endocardial Fibroelastosis

Endocardial fibroelastosis (EFE) is diffuse thickening of the ventricular endocardium by layered collagen and elastic fibres. The left ventricle is affected most often. This is not merely a thickened lining: the fibroelastic layer restricts the myocardium beneath it, so the ventricle may both fill poorly during diastole and contract inefficiently during systole. In a fetus or newborn, the same process can impair ventricular growth. A left ventricle exposed to abnormal pressure or flow may become borderline in size, while the accumulating fibroelastic layer further limits its ability to support a two-ventricle circulation. In an older infant or child, the phenotype may look more like dilated cardiomyopathy, restrictive physiology, or a mixture of both. The current pathogenic model is reactive rather than simply idiopathic. Abnormal flow or loading conditions and endocardial ischaemic injury can provoke endothelial-to-mesenchymal transition (EndMT). Endocardial endothelial cells acquire a mesenchymal, matrix-producing behaviour, laying down the collagen and elastic fibres that form EFE. This mechanism explains why EFE commonly accompanies another cardiac problem instead of appearing as an isolated disease. The physiological result is reduced effective cardiac output....