Frequency of anti-heparin-PF4 complex antibodies (HIT antibodies) in uremic patients on chronic intermittent hemodialysis

The aim of this study was to determine the frequency of heparin/platelet factor (PF) 4 complex antibodies in 305 uremic patients treated with chronic intermittent hemodialysis using unfractionated heparin or low-molecular-weight heparin for 3 months. Heparin-induced thrombocytopenia (HIT) antibodies were detected by ELISA in 7 patients (2.3%) who had no history of HIT. Two patients abruptly developed HIT associated with the formation of clots in the extracorporeal circuit after they were found to be carrying HIT antibodies. These patients were suspected to have a similar trigger: an increased dose of recombinant human erythropoietin (rHuEPO). The drug might induce parallel changes in hematocrit (Ht) levels and platelet counts until the onset of HIT. After the onset of HIT, a parallel phenomenon between Ht and platelet counts was not found because of the thrombocytopenia due to HIT. Although HIT onset has been reported during the initial phase of dialysis sessions, there have been few reports on the onset of HIT in uremic patients on dialysis with long-term heparin anticoagulation. In this study, HIT was observed in 2 uremic patients on chronic dialysis with intermittent use of heparin. In some patients on chronic intermittent dialysis carrying HIT antibodies, HIT may occur following rHuEPO treatment. The presence of HIT should be borne in mind in chronic dialysis patients carrying HIT antibodies for 3 months or more.     

Multivessel coronary thrombosis resulting from heparin induced thrombocytopenia

Thrombosis associated with a drop in the platelet count may occur in 33-50% of the patients who develop heparin-induced thrombocytopenia (HIT) during treatment with unfractionated heparin. We report the case of a 63-year-old man who was treated with unfractionated heparin following a non-ST segment elevation myocardial infarction (NSTEMI). He developed an acute ST segment elevation infarction (STEMI) on day 3 with an associated severe thrombocytopenia. He was successfully treated with percutaneous intervention and aspiration of coronary thrombus from the right coronary artery and the left circulflex artery, followed by an infusion a direct thrombin inhibitor lepirudin/bivalirudin. He made an excellent recovery.     

Improved laboratory confirmation of heparin-induced thrombocytopenia type II. Time course of antibodies and combination of antigen and biologic assays

We studied whether laboratory confirmation of heparin-induced thrombocytopenia (HIT) can be improved after antigen clearance by determining free antibody and combining the results of an antigenic and a biologic assay. Blood samples taken over 40 days in 14 patients with HIT with thromboembolism underwent fluorescence-linked immunofiltration and the carbon 14-serotonin release assays. Of the 14 patients, 11 showed positive results in both assays at day 1 after stopping heparin. The 3 patients with negative results seroconverted in one or both assays during the subsequent 7 days. Combining the positive results of the assays increased the sensitivity from 85% at day 1 to 100% at day 7. Assay results became negative in all patients within 40 days. The platelet count normalized between days 2 and 9 after withdrawal of heparin. It is assumed that the free antibody can be detected after withdrawal of heparin and after clearance of the platelet factor 4-heparin complex in patients with HIT.     

Pituitary Metastasis Presenting as Ischemic Pituitary Apoplexy Following Heparin-induced Thrombocytopenia

Pituitary apoplexy (PA) typically results from infarction or hemorrhage in a pituitary adenoma, while PA in nonadenomatous pituitary gland is uncommon. Prothrombotic states have never been recognized as precipitating factors for PA. The authors report a case of an elderly female who received prophylactic fractionated heparin therapy due to sepsis, consequent rhabdomyolysis, and overt disseminated intravascular coagulation. On the seventh day of heparin therapy, she reported sudden vision loss, ptosis, diplopia, and severe headache. Severe thrombocytopenia and positive antibodies to the complex of platelet factor 4 and heparin confirmed heparin-induced thrombocytopenia type 2 (HIT). Magnetic resonance imaging disclosed a homogenous pituitary tumor mass with pronounced sphenoid sinus mucosa thickening and two hypointense zones within the tumor mass on contrast-enhanced images consistent with focal ischemic necrosis. The tumor was confirmed to be squamous cell carcinoma with no signs of necrosis. Ischemic necrosis was found within marginal pituitary tissue. This is the first reported case of ischemic PA associated with pituitary metastasis and the first case in which HIT triggered PA. Our case demonstrates that prothrombotic states such as HIT can precipitate ischemic PA. Pituitary metastasis can present with ischemic PA, but radiological features differ from those described in pituitary adenomas. Segregated low-signal intensity zones within the tumor mass on postcontrast images indicate partial infarction of the tumor, which could be a special feature of ischemic PA in pituitary metastasis and has never been described in pituitary adenomas. These are all novel findings and might enlighten the pathogenesis of PA.     

Preexisting antibodies to platelet factor 4-heparin complexes in patients with acute coronary syndrome who have no history of heparin exposure

Preexisting heparin-induced thrombocytopenia (HIT) antibodies are detected in some patients who have not previously been exposed to any kind of heparin. However, the role of preexisting HIT antibodies in acute coronary syndrome (ACS) is still unknown. This study was carried out to clarify the role of preexisting HIT antibodies in patients with ACS. Forty patients with ACS who had not been exposed to any kind of heparin via the venous or subcutaneous route or heparin-coated materials and had undergone percutaneous coronary intervention (PCI) under heparin anticoagulation within 6 h from the onset of ACS were chosen from the medical records in the cardiac emergency department. As a control of the ACS patients, 51 patients with angina pectoris who underwent elective PCI under heparin anticoagulation were chosen in the same manner as the ACS patients. Preexisting HIT antibodies were detected by ELISA in 6 patients. Two of the 6 patients developed HIT and 1 patient experienced thrombosis requiring intracoronary thrombolytic therapy. Thrombotic complications during and immediately after PCI in the very early stage after heparin administration were found in 4 of 6 patients with preexisting HIT antibodies. The frequency of preexisting HIT antibodies in ACS patients was significantly increased in comparison with that in non-ACS patients. The odds ratio of the risk of thrombotic complication between ACS and non-ACS patients was estimated at 8.82 (95% CI: 1.3-63). Also, preexisting HIT antibodies in ACS patients significantly increased the risk of thrombotic complications compared with ACS without preexisting HIT antibodies. In conclusion, ACS patients with positive HIT antibodies have an increased risk of thrombotic complications during PCI performed under anticoagulation with heparin.     

Evolution of superficial vein thrombosis treated with defibrotide: comparison with low dose subcutaneous heparin

Forty patients with superficial vein thrombosis (SVT) or thrombophlebitis were randomly treated either with defibrotide (20) an antithrombotic/profibrinolytic drug or with low-dose subcutaneous heparin [LDSH] (20) for 3 weeks. The efficacy of the two treatments was evaluated by means of computerized thermography monitoring the decrease of the areas at maximum temperature (AMT) and using an analogue scale line to evaluate signs and symptoms. Defibrotide was found to be significantly more effective than LDSH in decreasing both AMT and analogue score after 2 and 3 weeks. By enhancing endogenous fibrinolysis, defibrotide reduced the deposition of fibrin, the ensuing inflammatory response and the production of new thrombi in the affected veins. This was shown by the progressive decrease in the hyperthermic areas. Thanks to its activity defibrotide may be able to promote a faster removal of thrombi and reduce the continuous formation of new thrombi in the inflamed veins.     

Heparin-induced thrombocytopenia: pathophysiology and new treatment options

Heparin induced thrombocytopenia (HIT) is a severe complication of heparin therapy. It is generally accompanied by a paradoxical decrease in platelets leading to activation of platelets and of the coagulation system. HIT type I is a mild, transient, non-immune disorder. HIT type II is an immune-mediated reaction towards neo-antigen on PF4, which is platelet factor 4 (PF4) that is exposed upon binding to heparins. A low sulfated octasaccharide is required for binding to PF4. The generated immunoglobulines bridge platelets by binding to the FcgRIIa-receptor. In patients with HIT type II heparin/LMW-heparin has to be discontinued immediately upon clinical suspicion. Diagnosis can be confirmed by laboratory tests. As patients are at high risk for or because they have developed thromboembolism, anticoagulation is mandatory, despite thrombocytopenia. Treatment options are danaparoid, r-hirudin, bivalirudin, argatroban, dextransulfate, and dermatansulfate. In future, fondaparinux and ximelagatran may be considered for treatment.     

Lack of plasminogen activator inhibitor-1 enhances the preventive effect of DX-9065a, a selective factor Xa inhibitor, on venous thrombus and acute pulmonary embolism in mice

We have studied the physiological effects of DX-9065a, a selective factor Xa (FXa) inhibitor, and heparin in experimental venous thrombus and acute pulmonary embolism. Moreover, the effects of these compounds were also evaluated under the condition of plasminogen activator inhibitor-1 (PAI-1) deficiency. A thrombus was induced in the murine femoral vein. The compounds prolonged the time to occlusion in a dose-dependent manner. Pulmonary embolism was induced by continuous induction of venous thrombi in the left jugular vein. The mortality of mice increased time-dependently. Histological evidence of thromboembolism in the lung was obtained in all mice. Treatment with DX-9065a, but not heparin, reduced the mortality at 6 h after initiation of venous thrombi. In separate experiments, pulmonary thromboembolism was induced in PAI-1 knockout mice. The mortality in PAI-1 knockout mice was reduced compared with that of wild-type mice. Moreover, when DX- 9065a was administered to PAI-1 knockout mice with pulmonary thromboembolism, mice survived well without marked bleeding. These findings indicate that the dual inhibition of coagulation FXa and PAI-1 could be beneficial in the treatment of acute pulmonary embolism.     

New developments in diagnosis and treatment of heparin-induced thrombocytopenia

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.     

articles

Thromboembolic events are serious but rare complications followingovarian stimulation for in-vitro fertilization (IVF). We reporta case of severe ovarian hyperstimulation syndrome (OHSS), presentingin a second IVF cycle with a late complication of right internaljugular vein thrombosis despite mini-dose heparin prophylaxis.Thrombosis and thromboembolism as late complications of OHSShave been reported by others but not after prophylactic heparinization.The patient was successfully treated with heparin and the twinpregnancy is ongoing. In pregnant patients with severe OHSSconsideration should be given to treatment with low dose heparinthroughout the first trimester to prevent the serious complicationsof thrombosis and thromboembolism.     

Anti-platelet factor 4/heparin antibodies from patients with heparin-induced thrombocytopenia provoke direct activation of microvascular endothelial cells.

Heparin-induced thrombocytopenia (HIT) is a serious complication that occurs in approximately 1-5% of patients treated with heparin and may be associated with severe thrombotic events. HIT is mediated by antibodies directed mostly to epitope(s) formed by complexes between heparin or other anionic mucopolysaccharides and platelet factor 4 (PF4). Anti-PF4/heparin IgG antibodies from six patients with HIT were affinity purified and assessed for interaction with human microvascular and macrovascular endothelial cells (EC). The antibodies directly activated primary cultures of human bone marrow microvascular EC (HBMEC) and SV40 immortalized HBMEC (TrHBMEC) only in the presence of PF4, but did not activate macrovascular human umbilical vein EC (HUVEC) under the same conditions. These antibodies were found to bind to TrHBMEC through the F(ab)(2) portion of the anti-PF4/heparin IgG. TrHBMEC activation was characterized by an augmented release of IL-6, von Willebrand factor, soluble thrombomodulin, and by an elevated expression of the adhesion molecules P-selectin, E-selectin and vascular cellular endothelial molecule-I to different degrees. Enhanced monocyte adhesion to PF4/heparin antibody-treated TrHBMEC (33-72% adhesion) was also observed. None of these effects occurred with unstimulated HUVEC. However, pre-treatment of HUVEC with tumor necrosis factor-alpha resulted in the same changes observed with microvascular EC exposed to the HIT antibodies. Our findings indicate that anti-PF4/heparin antibodies directly activate microvascular EC while interaction with macrovascular EC requires pre-activation. These results may explain some of the specific clinical manifestations in HIT.     

High-Dose Intravenous γ-Globulins for Heparin-Induced Thrombocytopenia: A Prompt Response

Heparin-induced thrombocytopenia (HIT) is a common drug induced autoimmune condition. The thrombocytopenia is caused in most cases by an antibody directed against the complex PF4/heparin. Recently, we have induced an experimental model of HIT by idiotypic manipulation. To confirm further the idiotypic involvement of HIT, we have treated successfully three patients with HIT with high-dose intravenous -globulin (IVIG). Our three patients join other two cases previously reported who were treated with IVIG and point to the efficacy of this type of therapy with minimal side effects. IVIG suppression of the anti-PF4/heparin autoantibody may support the idiotypic etiology of HIT.     

Intracranial venous thrombosis in relation to pregnancy and delivery

160 women who had died during pregnancy or after delivery were studied. Intracranial venous thrombosis (ICVT) was found in 10 (6.25%) cases. Most often extensive dural sinus phlebothrombosis and rarely isolated meningeal or cerebral phlebothrombosis were observed. Multiple thrombi in cerebral microcirculation presented the most characteristic morphological feature in all cases. Disseminated intravascular coagulation (DIC) with microthrombi in two or more parenchymal organs was found in 8 cases. Delayed clinical onset and prolonged progressive course was most frequently observed. Persistent headache, haemiparesis or haemiplegia, convulsions, epileptic seizures, disturbances in consciousness and coma occurred most often. These clinical manifestations were due to multiple haemorrhagic or ischaemic cerebral infarctions and in a single case to haemorrhage. The discussion was centered on the assumption that ICVT in pregnant and parturient women might be a distinct clinicoanatomical form of DIC.     

Role of newly developed technology in blood coagulation disorders

Clarification of blood coagulation disorders has been made progress based on newly developed technologies. ANTITHROMBIN III: In 1979, studies were carried out on antithrombin III(AT III) as a blood coagulation inhibitor from the first Japanese case of congenital AT III deficiency found in the laboratory sample. An alternative anticoagulant to maintain fluidity in extracorporeal circuit in an AT III deficient patient requiring hemodialysis was needed. In 1989, it was firstly introduced argatroban, a synthetic thrombin inhibitor as an alternative anticoagulant instead of human antithrombin III concentrate plus heparin regimen during hemodialysis. In 1992, success of good delivery in pregnant woman with an AT III deficiency was obtained to maintain normal level of AT III by the concentrates. DYSFIBRINOGENEMIA: Two families of congenital dysfibrinogenemia in clue to abnormally high levels of serum fibrinogen degradation products(FDP) were found. Polymerization detect due to dysfibrinogenemia induced high level of serum FDP and normal level of fibrin d-dimer products. HEPARIN COFACTOR II DEFICIENCY: A patient with congenital heparin cofactor II(HCII) deficiency was found in clue to four episodes of repeated restenosis under heparin-anticoagulated coronary angioplasty. For preventing the restenosis, argatroban as an alternative of heparin was used during coronary angioplasty. No restenosis after the angioplasty was appeared in anticoagulation with argatroban. Genetic analysis of the HCII was described that gene protein is secreted normally, but rapidly degraded in the circulation. FACTOR VII: In Japanese elderly, increase of Factor VII clotting activity was found to relate to high risk of cardiovascular disease. Elevation of activated FVII(FVIIa) as an activation marker of FVII in cardiovascular disease indicates to be an independent risk factor for cardiovascular disease. HEPARIN INDUCED THROMBOCYTOPENIA: HIT: HIT is believed to be less frequent in Japanese because of lack of recognition due to poor understanding of HIT's paradox. A survey in Japanese indicated to be no less frequent compared with that of the West. A causativity for HIT has been identified as antibodies against PF4/heparin complexes. As detection of the antibodies can easily be done by ELISA test, the test is desirable to become popular. Treatment for HIT is recommended to stop heparin and start a thrombin inhibitor. In Japan, argatroban and nafamostat mesilate are selected as an alternative agent for HIT, but both drugs have no approval for Japanese HIT patients.     

Heparin-induced thrombocytopenia (HIT): pathogenesis, laboratory test, and treatment

Heparin-induced thrombocytopenia(HIT) due to immunological mechanisms is known as an important adverse reaction to heparin treatment, and heparin treatment should be applied while keeping in mind the risk of onset of HIT 5-14 days after the initiation of heparin. The presence of HIT had not been fully recognized in clinical practice in Japan despite the management of HIT being well confirmed in Western countries. Recognition of HIT has increased since argatroban, a direct thrombin inhibitor, obtained the approval of the FDA for prevention and treatment of HIT. Although the incidence of HIT in Japan has not yet been clarified, there is some evidence that HIT is encountered in critically ill patients undergoing heparin anticoagulation. Clinical diagnosis of HIT is performed by means of thrombocytopenia of a drop of 50% or 100 x 10(30/microl for 5 -14 days after starting heparin treatment. Confirmatory laboratory tests examine whether the patients have antibodies against heparin/PF4 complexes or not. Two assay tests for detecting heparin/PF4 complex antibodies are available in Japan. As a functional test, the heparin-induced platelet aggregation method is easily performed and the result is obtained in a short time. The result of the test has, however, been misleading due to the selection of donors. Low platelet activity of the donors on the addition of heparin induces a negative response in spite of positive antibodies in the sample. Before testing samples, it is important to check heparin reactivity of the donor's platelets. Enzyme immunoassay detecting the antibodies is available as a commercial kit. Sensitivity obtained by enzyme immunoassay is very high and often introduces false-positives. Careful attention to interpretation of the result is required. Treatment of HIT should be started at the time of recognition of thrombocytopenia while antibody testing for HIT is performed. As an alternative anticoagulant to heparin, argatroban should immediately be applied to avoid complication of thrombosis. Thrombocytopenia and hypercoagulability quickly recover to the preheparin level by the appropriate use of argatroban.     

Malignant fibrous histiocytoma of the heart presenting as unilateral pulmonary thromboembolism and infarct

A malignant fibrous histiocytoma of the heart located at the pulmonic valve and thrombotic occlusion of branches of the left pulmonary artery with pulmonary infarct were found at autopsy in a 77-year-old man. The thrombi contained malignant cells. The patient had undergone left upper lobectomy four years earlier for thromboembolism with infarct, and review of the slides from that procedure revealed similar malignant cells within thrombi. This case is remarkable for the slow growth of the neoplasm and the prolonged survival of the patient, without specific therapy.     

Pathogenicity of human anti-platelet factor 4 (PF4)/heparin in vivo: generation of mouse anti-PF4/heparin and induction of thrombocytopenia by heparin

Heparin-induced thrombocytopenia/thrombosis (HIT) is a severe thrombotic disorder that occurs in ≈1% of patients treated with heparin. Affected patients commonly develop antibodies that recognize PF4/heparin complexes that may form on the surface of activated platelets and on the endothelium. However, it has not been established that anti-PF4/heparin antibodies are responsible for the clinical manifestations of HIT. To address this issue, we employed a recently developed model of active immunity to study the effect of IgG anti-PF4/heparin antibody in vivo. In previous studies we have shown that it is possible to induce autoimmune diseases such as systemic lupus erythematosus (SLE), anti-phospholipid syndrome (APS) or vasculitis in naive mice by active immunization with anti-DNA, anti-cardiolipin and anti-neutrophil cytoplasmic antibodies, respectively. Immunized animals develop anti-idiotypic antibodies (Ab₂) and, after 2–4 months, anti-anti-idiotypic antibodies (Ab₃). Ab₃s generated in this manner often simulate the binding activity of Ab₁ and their expression correlates with the development of specific clinical manifestations typical of the respective human disease. Based on this experience, naive BALB/c mice were immunized with IgG anti-PF4/heparin antibodies isolated from two patients with HIT. The actively immunized mice developed mouse anti-PF4/heparin antibody (Ab₃). Administration of unfractionated heparin, but not low molecular weight heparin (LMWH), to the actively immunized animals induced thrombocytopenia by day 4 of drug exposure. There was no evidence of thrombosis. The results of this study support the importance of anti-PF4/heparin antibodies in the pathogenesis of HIT. Further, this model may help to elucidate the factors responsible for thrombosis as well as providing means to assess new treatment options for patients with this disorder.     

Development of a high-pressure liquid chromatography method for diagnosis of heparin-induced thrombocytopenia

Owing to the disadvantage of radioactivity of the carbon 14 serotonin release assay and the time-consuming procedure of the enzyme immunoassay, we developed a high-pressure liquid chromatography (HPLC) method to detect serotonin released from donor platelets in the presence of heparins and serum samples from patients with heparin-induced thrombocytopenia (HIT). Samples were analyzed from 60 healthy control subjects, 19 patients with HIT, and 20 patients without HIT after incubation with heparin, low-molecular-weight heparin (LMWH), and danaparoid. Serotonin release was measured from platelets, 300 x 10(3)/microL, by HPLC. Serotonin eluted as a single peak from the HPLC column. Serum samples from patients with HIT released 5.5 to 352.5 and 6.6 to 1,533.3 ng/mL of serotonin from platelets in the presence of 0.2 IU/mL of heparin and LMWH, respectively. In the presence of 0 IU/mL of heparin, LMWH, danaparoid, and control samples, less than 2.5 ng/mL of serotonin were released. The HPLC method permits a rapid, sensitive, and quantitative determination of serotonin released from donor platelets for laboratory confirmation of HIT.     

The timing of a positive test result for heparin-induced thrombocytopenia relative to the platelet count and anticoagulant therapy in 43 consecutive cases

We studied the timing of a positive heparin-induced thrombocytopenia (HIT) test result relative to changes in platelet count and anticoagulant use. We obtained platelet counts in 100 consecutive HIT+ cases before, during, and after heparin therapy; 43 cases met study criteria and were included in study part 1. In part 2, platelet counts at the time of the HIT test in 2 groups (100 each HIT+ and HIT- cases) were compared. In part 1, cases could be divided into 4 groups based on the diagnosis of HIT relative to platelet counts (1, within 1-2 days of a major drop in platelet count [11.6%]; 2, after > 2 days of a major fall in platelet count [41.9%]; 3, in patients with already low platelet counts [27.9%]; 4, after platelet count was rising [18.6%]). In study part 2, the mean platelet counts for the HIT+ and HIT- groups were almost identical. HIT should be suspected in any thrombotic patient who had a previous decline in platelet count, has a low platelet count, or has a rising platelet count after a previous decline in association with heparin exposure. In study part 2, 1 platelet count value at the time of the HIT test did not provide useful information.