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Atherosclerosis and Thrombus Formation
Potential Outcomes of Plaque Fissuring
 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,
as sudden death) may be precipitated by thrombosis on atherosclerotic
plaques. In these episodes, the size of the thrombus
in 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.
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Stroke Education
