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2134 Part XII Hemostasis and Thrombosis

Fig. 145.2 COMPUTED TOMOGRAPHY OF BRAIN WITH LEFT
HEMISPHERIC ISCHEMIC STROKE.

Fig. 145.1 COMPUTED TOMOGRAPHY OF BRAIN WITH RIGHT
INTRACEREBRAL HEMORRHAGE. Cardioembolism
Approximately 14%–30% of all ischemic strokes are caused by car-
dioembolism, with marked regional variation. A number of condi-
TABLE Traditional Risk Factors for Ischemic Stroke tions predispose to cardioembolism, originating from the venous
145.1 system (paradoxical embolism), intracardiac (e.g., atrial fibrillation),
Risk Factor PAR (99% CI) or postcardiac (aortic arch disease).
Hypertension (self-reported history or blood 47.9% (45.1–50.6) Precardiac
pressure ≥140/90 mmHg) Paradoxical emboli occur when emboli that arise in the venous circula-
Current smoking a 12.4% (10.2–14.9) tion (e.g., from deep vein thrombosis) cross into the arterial circulation
Diabetes mellitus 3.9% (1.9–7.6%) through a patent foramen ovale (PFO), atrial septal defect (ASD), or
a pulmonary arteriovenous malformation (AVM). PFO is found in up
Ratio of apoB to apoA1 26.8% (22.2–31.9) to 20% of the general population. A number of observational studies
Obesity (waist to hip ratio) 18.6% (13.3–25.3) have reported an association between first ischemic stroke and PFO,
Physical inactivity 35.8% (27.7–44.7) particularly in younger patients, but PFO has not been shown to be a
risk factor for recurrent ischemic stroke. Atrial septal aneurysm, a
Diet risk score 23.2% (18.2–28.9) protrusion of part of the atrial septum through the fossa ovalis into the
Alcohol consumption (current) 5.8% (3.4–9.7) right or left atrium, is associated with an increased risk of ischemic
Psychosocial factors 17.4% (13.1–22.6) stroke, particularly when it occurs in conjunction with a PFO.
Cardiac etiologies 9.1% (8.0–10.2) Intracardiac
a Comparator for current smoker and alcohol intake is never or former. Left-sided cardiac sources of emboli include left atrial thrombus
Apo, Apolipoprotein; CI, confidence interval; PAR, population-attributable risk. secondary to atrial fibrillation or flutter, left ventricle thrombus
From O’Donnell MJ, Chin SL, Rangarajan S, et al: Global and regional effects of
potentially modifiable risk factors associated with acute stroke in 32 countries subsequent to a transmural myocardial infarction, akinetic segments
(INTERSTROKE): a case-control study. Lancet 388:761, 2016. of myocardium with a low ejection fraction in the setting of an old
myocardial infarction, cardiac tumors such as left atrial myxoma, and
abnormalities of the mitral valve (both native and artificial). Atrial
fibrillation or flutter is a significant risk factor for stroke, associated
occlusion with resultant hypoperfusion (e.g., watershed infarction). with a fivefold increase in risk. In North America and Europe, about
Large-vessel atherosclerosis accounts for about 20% of all ischemic 25% of all ischemic strokes are attributed to atrial fibrillation, a
strokes in high-income countries, and is predominantly extracranial proportion that increases with older age. After acute myocardial
in origin. Intracranial atherosclerosis has been reported to account infarction, mural thrombi can arise in the presence of left ventricular
for up to 33%–50% of ischemic strokes in parts of Asia (e.g., China aneurysms, akinetic segments of left ventricular myocardium, or
and Thailand), but it is a much less common cause of acute stroke new-onset atrial fibrillation or flutter. Congestive heart failure is also
in North America and Europe. Arterial dissection, the third leading an independent risk factor for stroke and is associated with a two- to
cause of ischemic stroke in young people, can lead to ischemic stroke threefold increased relative risk of ischemic stroke. Valvular heart
either by local occlusion or distal thromboembolism. Predisposing disease can involve both native (e.g., rheumatic heart disease) and
factors for dissection include trauma and underlying arteriopathies, prosthetic heart valves. Of native valvular disease, mitral stenosis has
such as fibromuscular dysplasia. Less common large-vessel mecha- the strongest association with ischemic stroke; mitral annular calcifi-
nisms of ischemic stroke include moyamoya disease, Fabry disease, cation and mitral valve prolapse have weaker associations. Mitral
and large-vessel arteritis (e.g., Takayasu arteritis and giant-cell stenosis is also commonly associated with atrial fibrillation, further
arteritis). increasing the risk of ischemic stroke. Emboli can also arise from