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Other risk factors for DVT: I already mentioned
cancer, but one can have a recent trauma that
injures the vein and, therefore, satisfies
Virchow's number-one requirement for DVT,
which is injury to the endothelium. Recent
surgery, the same. Immobility results in stasis.
Cancer: marked hypercoagulability. Estrogen
either in pregnancy or birth control pills
increases coagulability. And of course, as
we've already mentioned, prior DVT or pulmonary
embolism increases the risk for having it
occur again.
Again, just to reiterate: Here are some of
the inherited hypercoagulable states:
• Protein C or protein S deficiency
• Factor V Leiden or antithrombin III deficiency
• There can be—particularly in patients
with systemic lupus erythematosus—a clotting
antibody that increases the risk for blood
clots forming.
• Some patients are born with a very high
level of an amino acid, homocysteine. That
increases the tendency for clotting.
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• And again, some patients with lupus will
actually have a protein that activates the
clotting system, different from the antiphospholipid
antibody. (Some patients will have elevated
antiphospholipid antibodies without having
lupus.)
Hormonal therapy: It's important to stress
this. Hormonal therapy, either pregnant…
given as contraceptive pills or pregnancy,
where there's high levels of female hormones,
increase the coagulability of the blood and,
therefore, increase the risk for DVT and pulmonary
embolism. So pregnancy or pseudopregnancy
(which is induced by the oral contraceptive
pills) or postmenopausal hormone replacement
all increase production of clotting factors
in the liver. This leads to a hypercoagulable
state—in other words, an increased propensity
of the blood to clot. The increased risk for
intravascular disease events—myocardial
infarction, stroke, DVT / pulmonary embolism—all
occur with these products and with these states,
because the blood is at a higher likelihood
of clotting. And by the way, if you add cigarette
smoking on top of one of these things—for
example, birth control pills—you markedly
further increase the risk for developing DVT
and PE, which is one of the reasons we strongly
recommend that women who are taking birth
control pills not smoke.