Definition
nDeep
vein thrombosis is the formation of a blood clot in one of the deep veins
of the body, usually in the leg
ETIOLOGY
nDVT
ususally originates in the lower extremity venous level ,starting at the
calf vein level and progressing proximally to involve popliteal ,femoral
,or iliac system. .80 -90 % pulmonary emboli originates here .
Virchow tried
nMore
than 100 years ago, Virchow described a triad of factors of
nvenous
stasis,
nendothelial
damage, and
n
hypercoagulable state
Venous stasis
nprolonged
bed rest (4 days or more)
nA
cast on the leg
nLimb
paralysis from stroke or spinal cord injury
nextended
travel in a vehicle
Hypercoagulability
nSurgery
and trauma responsible
for up to 40% of all thromboembolic disease
nMalignancy
nIncreased
estrogen (due to a fall in protein ‘S) Increased estrogen occurs during
nall
stages of pregnancy—
nthe
first three months postpartum,
nafter
elective abortion, and
n
during treatment with oral contraceptive pills
Inherited disorders of coagulation
Ø
deficiencies of protein ‘S,
Ø’
protein ‘C,’ and
Ø
antithrombin III.
Acquired disorders of coagulation
nnephrotic
syndrome results in urinary loss of antithrombin III, this diagnosis
should be considered in children presenting with thromboembolic disease
nAntiphospholipid
antibodies accelerate coagulation and include the lupus anticoagulant and
anticardiolipin antibodies.
Inflammatory processes, such as
•
systemic lupus erythematosus (SLE),
•
sickle cell disease, and
•inflammatory
bowel disease (IBD),
also predispose to thrombosis, presumably due to
hypercoagulability
Endothelial Injury
nTrauma,
n
surgery, and
n
invasive procedure may disrupt venous integrity
nIatrogenic
causes of venous thrombosis are increasing due to the widespread use of
central venous catheters, particularly subclavian and internal jugular
lines. These lines are an important cause of upper extremity DVT,
particularly in children.
Clinical
Pathophysiology
|