Pathology of stable coronary artery disease
Coronary artery disease remains the major cause of morbidity and mortality on a global scale. Intimal thickening and fatty streaks represent early adaptive vascular changes, which are often regressive. Pathological intimal thickening represents the earliest progressive atherosclerotic lesion characterized by a focal accumulation of smooth muscle cells and acellular areas, often associated with lipid pools. Fibroatheroma is characterized by a necrotic core and can be split into early and late fibroatheroma, where macrophage apoptosis and defective efferocytosis play important roles in lesion progression. Intraplaque hypoxia is believed to result in neovascularization with subsequent intraplaque haemorrhage because of immature and leaky microvessels. Due to excessive cholesterol in remnants of erythrocyte membranes, intraplaque haemorrhage may result in rapid progression of necrotic core and plaque destabilization. Healed plaque rupture has been well delineated as an important mechanism of gradual luminal narrowing, where changes in collagen deposition allow recognition of rupture and healing sites. Calcification results from apoptosis of smooth muscle cells and macrophages or may also be caused by active release of cellular vesicles involved in calcium haemostasis. Extracellular matrix changes are associated with progression of atherosclerosis, while integrin signalling has been recognized as an important outside-in transcellular target of the inflammatory response.