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Cerebrovascular disease and risk of stroke
Submitted by Dr. Yasser
Mokhtar, MD. Dept. of internal medicine. School of
medicine, University of South Dakota.
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Stroke is a loss of cerebral
function with symptoms lasting >24 hrs or death due to vascular
disease |
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8. Oral contraceptive use
Despite many studies, the role of contraceptives in stroke and in particular
thromboembolic still remains controversial (Longstreth and Swanson 1984). Unless
a user of oral contraceptives is also a cigarette smoker and over the age of
thirty years, the absolute risk of a serious vascular event is so low that there
is no great cause for concern (Croft and Hannaford 1989).
9. Transient ischemic attacks
Because TIAs are, in a sense, ischemic strokes that happen to recover within
twenty four hours, it is not surprising that they are a risk for stroke. Having
experienced a TIA, the risk of subsequent infarction is greatest within the
first month. About thirty six per cent of infarctions will occur within the
first month following a TIA and fifty per cent by the end of the first year,
thereafter the risk becomes much less (Toole 1984).
10. Blood viscosity
Blood flow in any given vessel is inversely proportional to the viscosity of
the blood flowing through it, as governed by Poiseuille?s law (Dintenfass et
al., 1985). The whole blood viscosity is largely influenced by hematocrit and
plasma viscosity, which in turn is largely influenced by the presence of
macromolecules such as fibrinogen. Data from the Framingham (Kannel et al.,
1972) and other studies (Wihelmsen 1984 and D?Agostino 1985) have shown both
elevated hematocrits and fibrinogen levels to be related to an increased risk of
stroke. Further studies showed that any effect of increasing hematocrit on risk
of stroke is weak and confounded by cigarette smoking, blood pressure and plasma
fibrinogen (LaRue et al., 1987). There is a strong and consistent relationship
between plasma fibrinogen and stroke. The association is attenuated by cigarette
smoking and other confounding variables (Cook and Ubben 1990, Rosengren et al.,
1990 and Qizilbash et al., 1991).
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