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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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2. Cardiac diseases
Cardiac diseases have been clearly associated with an increased risk of
ischemic stroke particularly atrial fibrillation, valvular heart disease,
myocardial infarction, coronary artery disease, congestive heart failure,
electrocardiographic evidence of left ventricular hypertrophy and perhaps mitral
valve prolapse.
Atrial fibrillation (AF)
This is the most potential cardiac source of embolism to the brain. AF is
usually non-rheumatic in developed countries. Both non-rheumatic and more so
rheumatic AF have been associated with stroke from postmortem (Hinton et al.,
1977) case control (Kempster et al., 1988) and cohort studies (Flegel et al.,
1987). AF even without valvular heart disease is strongly correlated with
stroke, especially embolic stroke (Wolf et al., 1983). AF prevalence is very
closely related to age so that most strokes caused by AF are in the very
elderly, where the proportion attributed to AF is highest (Wolf et al., 1991).
Some of the association must be coincidental because AF can be caused by
coronary heart disease and hypertensive heart disease both of which may be
associated with stroke by mechanisms other than embolism from the fibrillating
left atrium (Davies et al., 1987). In the Framingham study, AF was a strong
predictor of stroke with nearly a five-fold increased risk of stroke. In those
with coronary heart disease, or cardiac failure, AF doubled the stroke risk in
males and tripled the risk in females. With coexisting valvular disease, AF had
an even greater impact on the relative risk of stroke. Left ventricular
dysfunction and left atrial size determined by echocardiography were also
predictors of increased thromboembolic risk (Wolf et al., 1991).
Coronary artery disease
Independent of age coronary artery disease (myocardial infarction or angina)
is clearly associated with stroke. The evidence comes from postmortem (Stemmerman
et al., 1984), case control (Woo et al., 1991), and cohort studies (Kannel et
al., 1983). Data suggest that most of this association is causal (i.e. embolism
from the left ventricular thrombus complicating myocardial infarction) rather
than due to the coincidence of atheroma in coronary and cerebral circulation in
the same (predisposed) individuals (Dexter et al., 1987).
Cardiac failure is a further risk factor (Kannel et al., 1983).
ECG abnormalities reflecting hypertension or coronary heart disease
are, not surprisingly, risk factors for stroke (Knutsen et al., 1988 and Shaper
et al., 1991).
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