Clinical features of heparin-induced thrombocytopenia including risk factors for thrombosis A retrospective analysis of 408 patients
Andreas Greinacher1 , Beate Farner1 , Hartmut Kroll2 , Thomas Kohlmann³, Theodore E. Warkentin4 , Petra Eichler1
1 Institut für Immunologie und Transfusionsmedizin, Ernst-Moritz-Arndt-Universität Greifswald, Germany 2 Institut für Klinische Immunologie und Transfusionsmedizin, Justus-Liebig-Universität Giessen, Germany 3 Institut für Community Medicine, Ernst-Mori
Immune mediated heparin induced thrombocytopenia (HIT) is a
prothrombotic adverse effect of heparin. However, only a subgroup
of patients with HIT develops thromboembolic complications.
We aimed to identify risk factors for developing HITassociated
thrombosis.We analyzed a registry of patients with
clinical suspicion of HIT who tested positive using a sensitive
functional assay.Patient information was obtained by a standardized
questionnaire. By multivariate analysis the association of
age, gender, type of patient population, and magnitude of the platelet
count decline with the frequency, type (venous or arterial),
and temporal pattern of thrombotic events was assessed. In 408
HIT patients we observed predominance of venous thrombosis
(2.4:1), with 40% of patients developing a pulmonary embolism.
However, in the subgroup of post-cardiovascular surgery patients
there was predominance of arterial thrombosis (1:8.5).
The type of arterial thrombosis (limb artery thrombosis
> thrombotic stroke > myocardial infarction) was the converse
of that observed with typical atherothrombotic clots in non-HIT
populations. In 59.8% of patients HIT-related thrombosis manifested
either on the same day a platelet count decrease >50%
was documented (26.3%) or before the decrease in platelet
counts (33.5%).The most important risk factors for thrombosis
were orthopedic/trauma surgery and the magnitude of platelet
count decrease. HIT-associated thrombosis occurs in a considerable
proportion of patients before platelet counts decrease
by more than 50%.