Article

Thrombopénie induite à l'héparine et syndrome coronarien aigu

Service de réanimation et maladies infectieuses, centre hospitalier de Belfort-Montbéliard, 14, rue de Mulhouse, 90000 Belfort, France
Réanimation 04/2006; 15(2). DOI: 10.1016/j.reaurg.2005.12.025

ABSTRACT Heparin-induced thrombocytopenia (HIT) is a relatively common immune-mediated disorder due to the development of IgG antibody specific to platelet factor 4. More frequent with the use of unfractionated heparine after the 5th day of treatment, this complication is defined as a decrease in platelet count of up to 40% and/or

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    ABSTRACT: Heparin-induced thrombocytopenia (HIT) is a drug induced immune mediated thrombocytopenia that affects up to 3% of patients treated with unfractionated heparin (UFH). It is less frequent when low molecular weight heparins (LMWH) are used. Fondaparinux does not seem to induce HIT. A functional and an antigen assay should be performed to confirm the clinical diagnosis of HIT. Immediate cessation of heparin and start of compatible anticoagulant is mandatory when HIT is suspected clinically. Danaparoid (a heparinoid)and the direct thrombin inhibitors lepirudin and argatroban are available for this purpose. Short-term reexposure with heparin, for example during cardiopulmonary bypass, is possible in patients with history of HIT, provided HIT antiodies are no longer detectable. In children systematic data on treatment of HIT are lacking.
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    ABSTRACT: Heparin-induced thrombocytopenia (HIT) is a complication of heparin therapy caused by antibodies against a complex of platelet factor 4 and heparin. Fondaparinux (Arixtra) is a new synthetic selective factor Xa inhibitor. We performed a serologic study to determine the cross-reactivity of HIT sera with fondaparinux. Using a prospective, blinded study design, 39 clinically and serologically confirmed sera from patients with HIT and 15 control sera were sent to 3 different laboratories, each of which specialized in a particular HIT assay. These include the serotonin release assay, heparin-induced platelet agglutination assay, and platelet aggregation assay. Two of 82 assays (2.4%) performed in the presence of control sera were positive, both with unfractionated heparin. In the presence of HIT sera, 75 of 94 (79.8%) evaluable assays were positive with unfractionated heparin; fondaparinux was significantly (P < .001) less reactive than unfractionated heparin, only 3 of 91 evaluable assays (3.3%) being positive. Using flow cytometry, unlike unfractionated heparin, fondaparinux did not induce the binding of PAC1 and anti-CD62 monoclonal antibodies or of annexin V to platelets with HIT sera. Together, these results suggest that fondaparinux is nonreactive to HIT sera and raise the possibility that the drug may be used for prophylaxis and treatment of thrombosis in patients with a history of HIT.
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    ABSTRACT: A multicenter prospective study on the rate of seroconversion of antibodies to heparin-PF4 complexes (heparin-induced thrombocytopenia [HIT] antibodies) during and after heparin treatment for 4 weeks was carried out in Japanese patients with acute coronary syndrome (ACS). A total of 254 ACS patients treated with heparin were enrolled consecutively from 12 facilities of cardiology. Two patients with preexisting HIT antibodies were excluded from the analysis. The total seroconversion rate for four weeks during and after heparin treatment was 8.7% (n=22, 95% confidence interval [CI]: 5.9-13.1), including values of 3.2% (n=8) at the end of heparin infusion and 5.5% (n=14) at 4 weeks. Among 22 seroconverted patients, four developed HIT and two of the four had the complication of thrombosis. The incidence of HIT was 1.6% (n=4, 95% CI: 0.04-3.1). The risk for thromboembolic development was higher in the seroconverted patients (odds ratio, 17.4, 95% CI: 5.2-58.4, p<0.0001) than nonconverted patients. An analysis of factors affecting the seroconversion rate was carried out. The seroconversion rate for ACS patients who underwent percutaneous coronary intervention (PCI; n=163) was 12.3%, significantly higher than the 2.3% in patients who did not undergo PCI (n=89), leading to an odds ratio of 6.1 (95% CI: 1.4-26.7, p=0.009). A significant odds ratio was obtained for each factor affecting the seroconversion: 3.5 (95% CI: 1.3-9.9, p=0.014) for more than 5 days of heparin infusion, 3.0 (95% CI: 1.2-7.6, p=0.035) for a thrombotic history and 2.7 (95% CI: 1.1-6.8, p=0.039) for hyperlipidemia. No other factor, including age or diabetes mellitus, contributed to the seroconversion. Therefore, PCI, duration of heparin treatment and thrombotic history facilitated the seroconversion in ACS patients. PCI patients treated for more than 5 days with heparin showed a maximal seroconversion rate of 18.3% (95% CI: 13.8-22.2). This high rate in PCI patients did not interact with age, type of underlying disease of unstable angina or myocardial infarction or thrombotic history. In conclusion, ACS patients demonstrating seroconversion are at risk of thromboembolic development due to the likelihood of immunomediated endothelial dysfunction. The increase in the rate of seroconversion in ACS patients would be affected by factors such as PCI with mechanical stress, longer duration of heparin treatment, thrombotic history and presence of hyperlipidemia. If PCI is undertaken with heparin anticoagulation for more than 5 days, seroconversion would easily occur, and the seroconverted patients could subsequently suffer from HIT.
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