Page 378 - Essential Haematology

364 / Chapter 27 Thrombosis and antithrombotic therapy

struction of coronary artery thrombosis risk profi les
Table 27.2 Hereditary and acquired risk

based on sex, age, elevated blood pressure, high
factors for venous thrombosis.
levels of serum cholesterol, glucose intolerance,
cigarette smoking and electrocardiogram abnor- Hereditary haemostatic disorders
malities. Th ese profiles have allowed pre - Factor V Leiden

symptomatic assessment of young and apparently Prothrombin G20210A variant
fit subjects and are valuable in counselling a change Protein C defi ciency

in lifestyle or for recommending medical therapy Antithrombin defi ciency
in individuals at risk. Epidemiological evidence Protein S defi ciency
implicates four inflammatory markers, fi brinogen, Dysfi brinogenaemia

C - reactive protein, lipoprotein - associated phos- ABO blood group
pholipase A 2 and interleukin - 6 as predictive for
Hereditary or acquired haemostatic disorders
coronary heart disease. Raised plasma levels of factor VIII
Raised plasma levels of fi brinogen
Raised plasma levels of homocysteine
Venous t hrombosis
Acquired disorders
Lupus anticoagulant
Pathogenesis and r isk f actors
Oestrogen therapy (oral contraceptive and HRT)
’
Virchow s triad suggests that there are three compo- Heparin - induced thrombocytopenia
nents that are important in thrombus formation: Pregnancy and puerperium
Surgery, especially abdominal, hip and knee
1 Slowing down of blood fl ow; surgery
2 Hypercoagulability of the blood; and Major trauma
3 Vessel wall damage. Malignancy
Acutely ill hospitalized medical patients
For venous thrombosis, increased systemic
including cardiac or respiratory failure,
coagulability and stasis are most important, vessel
infection, infl ammatory bowel disorders
wall damage being less important than in arterial
Myeloproliferative disease
thrombosis, although it may be important in
Hyperviscosity, polycythaemia
patients with sepsis and indwelling catheters. Stasis
Stroke
allows the completion of blood coagulation at
Pelvic obstruction
the site of initiation of the thrombus (e.g. behind Nephrotic syndrome
the valve pockets of the leg veins in immobile Dehydration
patients). Varicose veins
Table 27.2 lists a number of recognized risk Age
factors. Obesity
Paroxysmal nocturnal haemoglobinuria
Beh ç et ’ s disease
Hereditary d isorders of h aemostasis
HRT, hormone replacement therapy.

The prevalence of inherited disorders associated
with increased risk of thrombosis is higher than that
of hereditary bleeding disorders. A hereditary
‘ thrombophilia ’ should be particularly suspected in Factor V L eiden g ene m utation ( a ctivated
young patients who develop spontaneous thrombo- p rotein C r esistance)
sis, recurrent DVTs (Fig. 27.2 ) or an unusual site

of thrombosis (e.g. axillary, splanchnic veins, sagit- This is the most common inherited cause of an
tal sinus). Several abnormalities are now well char- increased risk of venous thrombosis. It occurs in
acterized (Table 27.2 ). approximately 3 – 7% of Caucasian factor V alleles.