Heparin-induced thrombocytopenia and thrombosis syndrome (HITTS) is an
immune-mediated response to the administration of heparin that result
s in life-threatening thrombosis. The pathophysiology of HITTS remains
controversial. The onset of clinical symptoms and laboratory changes
is usually delayed 1-2 weeks after exposure to heparin. Thrombosis occ
urs in both the arterial and venous circulation with significant morbi
dity and mortality. Complications include deep venous thrombosis, pulm
onary embolus, stroke, myocardial infarction, chronic venous insuffici
ency, extremity ischemia, gangrene, and death. Diagnostic criteria for
HITTS include thrombocytopenia during heparin exposure, exclusion of
other causes such as sepsis or medications, resolution of thrombocytop
enia after withdrawal of heparin, demonstration of in vitro heparin-de
pendent platelet antibodies, and development of vascular thrombosis. D
espite having several disadvantages, the carbon-14-serotonin release a
ssay is the most sensitive and specific test for HITTS. Angiography as
an adjunct to other imaging modalities can document the presence, loc
ation, and extent of thrombus. Optimal treatment has not yet been defi
ned but should include immediate discontinuation of use of all heparin
products and heparin-coated catheters. In addition, alternate methods
of antithrombotic therapy should be considered. Ln severe cases, thro
mbolysis or thrombectomy may be warranted. Familiarity with the pathop
hysiology, clinical manifestations, complications, diagnostic criteria
, and treatment options associated with HITTS will enable timely recog
nition and facilitate prompt and effective treatment.