Thrombosis formation on atherosclerotic lesions and plaque rupture

Atherosclerosis is a silent chronic vascular pathology that is the cause of the majority of cardiovascular ischaemic events. The evolution of vascular disease involves a combination of endothelial dysfunction, extensive lipid deposition in the intima, exacerbated innate and adaptive immune responses, proliferation of vascular smooth muscle cells and remodelling of the extracellular matrix, resulting in the formation of an atherosclerotic plaque. High-risk plaques have a large acellular lipid-rich necrotic core with an overlying thin fibrous cap infiltrated by inflammatory cells and diffuse calcification. The formation of new fragile and leaky vessels that invade the expanding intima contributes to enlarge the necrotic core increasing the vulnerability of the plaque. In addition, biomechanical, haemodynamic and physical factors contribute to plaque destabilization. Upon erosion or rupture, these high-risk lipid-rich vulnerable plaques expose vascular structures or necrotic core components to the circulation, which causes the activation of tissue factor and the subsequent formation of a fibrin monolayer (coagulation cascade) and, concomitantly, the recruitment of circulating platelets and inflammatory cells. The interaction between exposed atherosclerotic plaque components, platelet receptors and coagulation factors eventually leads to platelet activation, aggregation and the subsequent formation of a superimposed thrombus (i.e. atherothrombosis) which may compromise the arterial lumen leading to the presentation of acute ischaemic syndromes. In this review, we will describe the progression of the atherosclerotic lesion along with the main morphological characteristics that predispose to plaque rupture, and discuss the multifaceted mechanisms that drive platelet activation and subsequent thrombus formation. Finally, we will consider the current scientific challenges and future research directions.