Most advanced plaques appear to progress from the early lesion very rapidly by means of Type II injury with resulting thrombus formation and its incorporation into the plaque [Ip JH, et al, 1994].
Thrombosis and incorporation of the surrounding thrombus into the plaque have been demonstrated in various stages of atherogenesis [Ip JH, et al, 1994]. In autopsy study of coronary arteries in patients with atherosclerotic syndromes, for example, nearly 17% of patients had fissures in atherosclerotic plaques and some cases overlying thrombi [Davies MJ. In: Julian DG, et al (eds). Thrombolysis in Cardiovascular Disease. New York, Marcel Dekker, 1989]. Moreover, studies have suggested that thrombus formation/organization and acute or subacute progression of atherosclerotic plaque is probably part of the same phenomenon [Wilcox JN, et al. J Clin Invest. 1988;82:1134].
Acute episodes of transient ischemia and ischemic stroke (as well as myocardial infarction, unstable angina, and sudden death) may be precipitated by thrombosis on atherosclerotic plaques. In these episodes, the size of the thrombus is an order of magnitude greater than the microscopic thrombi that contribute to plaque growth [Davies MJ. In: Colman RW, et al (eds). Hemostasis and Thrombosis: Basic Principles and Clinical Practice, Third Edition. Philadelphia, J.B. Lipincott Company, 1994:1225].
In this figure, initial plaque fissure may lead to one of two immediate outcomes: (1) The fissure is sealed and the incorporated thrombus undergoes fibrotic organization; or (2) the fissure leads to mural intraintimal and intraluminal thrombosis, resulting in partial or transient reduction in blood flow. Some transient ischemic attacks (TIAs) could be caused by this mechanism, but other factors such as increased viscosity, reduced vessel wall compliance, or other unknown factors also appear to be important.
Following intraintimal and intraluminal thrombosis, (3) the fissure may result in occlusive thrombosis which, if persistent, can lead to ischemic stroke or myocardial infarction, particularly in the absence of collateral flow.
Acute Ischemic Stroke: New Concepts of Care
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