Heparin-induced Thrombocytopenia, a Prothrombotic Disease

Profiling Heparin-Induced Thrombocytopenia (HIT) Antibodies in Hospitalized Patients With and Without Diabetes

Heparin (H) anticoagulation in populations characterized by elevated platelet factor 4 (PF4) frequently elicits PF4/H antibodies, presenting a risk of heparin-induced thrombocytopenia. Recent studies have shown that anti-PF4/H enzyme-linked immunosorbent assays (ELISAs) detect antibodies in individuals never exposed to heparin. Platelet factor 4/H cross-reactive antibodies may result from PF4-mediated defense responses to injury or infection. This study questioned whether patients with diabetes are more likely to develop the endogenous cross-reactive antibodies. A comparison of healthy volunteers versus hospitalized patients with or without diabetes showed no significant differences in the prevalence of PF4/H ELISA-positive results. However, the group of patients who had both diabetes and an infectious condition had higher median antibody titer compared to other patients with or without diabetes regardless of reason for hospitalization. Higher PF4/H titers were also associated with patients with diabetes who were not on any medical therapy. In the future, determining whether PF4/H cross-reactive antibodies sensitize patients to respond adversely to heparin anticoagulation or predispose patients to other complications may be relevant to diabetes care.

Heparin-Induced Thrombocytopenia and Thrombosis: Preventing your Thrombolysis Practice from Taking a HITT

Heparin-induced thrombocytopenia and thrombosis (HITT) is an under-recognized cause of deep venous thrombosis treatment failure and of complications during catheter-directed thrombolysis. After a review of HITT pathophysiology, diagnosis, and management, three different cases are presented in this article. Each case highlights subtleties and challenges of HITT diagnosis and management. An example of a practical approach to the diagnosis of HITT is presented.

[Heparin-induced thrombocytopenia type II (HIT II) : A medical-economic view]

BACKGROUND

In the context of inpatient and increasingly ambulatory thrombosis prophylaxis, heparins have been recognised as standard therapy for decades. In addition to the therapeutic benefit, therapy with heparins also entails the risk of undesirable side effects, such as bleeding and thrombocytopenia. Heparin-induced thrombocytopenia (HIT II) is deemed a serious side effect.

AIM

In the following work, HIT II is subjected to a medico-economic consideration (treatment, pharmaceuticals, subsequent costs due to possible complications) and, with regard to a possible HIT II prophylaxis, aspects of increasingly respected patient safety are also considered.

METHODS

In the context of a literature search the active ingredients argatroban and danaparoid, which are approved for HIT II treatment, were evaluated.

RESULTS

HIT II - especially in combination with thromboembolic complications - represents a medical-economic burden for the hospital. Although this is only an orientation guide, it shows that HIT II syndrome is not adequately cost-covered by the G‑DRG system. An early thrombosis prophylaxis with argatroban/danaparoid for HIT II risk patients should therefore be taken into account for medical-related as well as patient safety-relevant aspects. According to experience, the pharmaceutical supply for these medically needed products (anticoagulants) should be ensured for reasons of patient safety.

CONCLUSION

The risk of an immunological response to heparin therapy is known. Within the context of increased patient safety, thrombosis prophylaxis should be issued with a risk-adjusted prophylaxis.

Incidence of heparin-induced thrombocytopenia type II and postoperative recovery of platelet count in liver graft recipients: a retrospective cohort analysis

BACKGROUND

Thrombocytopenia in patients with end-stage liver disease is a common disorder caused mainly by portal hypertension, low levels of thrombopoetin, and endotoxemia. The impact of immune-mediated heparin-induced thrombocytopenia type II (HIT type II) as a cause of thrombocytopenia after liver transplantation is not yet understood, with few literature citations reporting contradictory results. The aim of our study was to demonstrate the perioperative course of thrombocytopenia after liver transplantation and determine the occurrence of clinical HIT type II.

METHOD

We retrospectively evaluated the medical records of 205 consecutive adult patients who underwent full-size liver transplantation between January 2006 and December 2010 due to end-stage or malignant liver disease. Preoperative platelet count, postoperative course of platelets, and clinical signs of HIT type II were analyzed.

RESULTS

A total of 155 (75.6%) of 205 patients had thrombocytopenia before transplantation, significantly influenced by Model of End-Stage Liver Disease score and liver cirrhosis. The platelet count exceeded 100,000/μL in most of the patients (n = 193) at a medium of 7 d. Regarding HIT II, there were four (1.95%) patients with a background of HIT type II.

CONCLUSIONS

The incidence of HIT in patients with end-stage hepatic failure is, with about 1.95%, rare. For further reduction of HIT type II, the use of intravenous heparin should be avoided and the prophylactic anticoagulation should be performed with low-molecular-weight heparin after normalization of platelet count.

A Rare Case of Acute Myocardial Infarction due to Coronary Artery Dissection and Heparin-Induced Thrombocytopenia

Although both coronary artery dissection and heparin-induced thrombocytopenia may provoke myocardial infarction, it is extremely rare for both conditions to develop simultaneously in a single patient. We report a case of a 69-year-old woman who sustained a head-on motor vehicle accident with associated chest trauma. During a subsequent hospitalization, she was exposed to subcutaneous heparin and developed significant thrombocytopenia. Shortly thereafter, she re-presented with an acute myocardial infarction. Coronary angiography revealed a spiral dissection with superimposed thrombosis within the right coronary artery, while laboratory testing confirmed the diagnosis of heparin induced thrombocytopenia. She was treated with catheter-based thrombectomy and adjunctive direct thrombin inhibitor therapy, followed by three months of systemic anticoagulation with warfarin. To our knowledge, this represents the first published case of a native vessel myocardial infarction due to the combination of coronary artery dissection and heparin-induced thrombocytopenia.

Donor heparinization is not a contraindication to liver transplantation even in recipients with acute heparin-induced thrombocytopenia type II: a case report and review of the literature

Heparin-induced thrombocytopenia (HIT) type II is caused by an immune-mediated side effect of heparin anticoagulation resulting in a clotting disorder. In the setting of urgent liver transplantation, the question arises whether a graft from a heparinized donor can be safely transplantated in a recipient with even acute heparin-induced thrombocytopenia type II. We report on a patient with end-stage liver disease and acute HIT II waiting for liver transplantation. Despite the risk of life-threatening complications, an organ procured from a heparinized donor was accepted. Assuming heparin residuals within the graft, the donor organ was flushed backtable with increased amounts of Wisconsin solution. The subsequent transplantation and the postoperative course were uneventful; neither thromboses nor graft dysfunction occurred. Even in acute episode of HIT II with circulating antibodies, a patient may receive an organ from a heparin-treated donor, if adequate precautions during organ preparation are observed.

Heparin-induced thrombocytopenia

In the last 7 decades heparin has remained the most commonly used anticoagulant. Its use is increasing, mainly due to the increase in the number of vascular interventions and aging population. The most feared complication of heparin use is heparin-induced thrombocytopenia (HIT). HIT is a clinicopathologic hypercoagulable, procoagulant prothrombotic condition in patients on heparin therapy, and decrease in platelet count by 50% or to less than 100,000, from 5 to 14 days of therapy. This prothrombotic hypercoagulable state in HIT patient is due to the combined effect of various factors, such as platelet activation, mainly the formation of PF4/heparin/IgG complex, stimulation of the intrinsic factor, and loss of anticoagulant effect of heparin. Diagnosis of HIT is done by clinical condition, heparin use, and timing of thrombocytopenia, and it is confirmed by either serotonin release assay or ELISA assay. Complications of HIT are venous/arterial thrombosis, skin gangrene, and acute platelet activation syndrome. Stopping heparin is the basic initial treatment, and Direct Thrombin Inhibitors (DTI) are medication of choice in these patients. A few routine but essential procedures performed by using heparin are hemodialysis, Percutaneous Coronary Intervention, and Cardiopulmonary Bypass; but it cannot be used if a patient develops HIT. HIT patients with unstable angina, thromboembolism, or indwelling devices, such as valve replacement or intraaortic balloon pump, will require alternative anticoagulation therapy. HIT can be prevented significantly by keeping heparin therapy shorter, avoiding bovine heparin, using low-molecular weight heparin, and stopping heparin use for flush and heparin lock.

Physiological changes in membrane-expressed platelet factor 4: implications in heparin-induced thrombocytopenia

BACKGROUND

Many heparin-induced thrombocytopenia (HIT) antibodies cause platelet activation in the serotonin release assay (SRA) in the absence of heparin. This in vitro observation may help unravel the mechanism of delayed-onset HIT, where seropositive patients develop thrombocytopenia and associated thrombosis after cessation of heparin.

OBJECTIVE

Studies were conducted to examine the relationship between platelet environment, surface PF4 expression, and the extent of heparin-independent platelet activation in the SRA.

METHODS

Ex vivo platelets were washed and labeled for SRA, then used either before or after 45 minutes of recovery at 37 degrees C. HIT antibody-mediated serotonin release in the absence of heparin was compared to the extent of surface staining of the platelets with fluorescent anti-human PF4 antibodies.

RESULTS

Handling of platelets for in vitro studies resulted in transient expression of surface PF4, and it was during this interval that platelets were most sensitive to activation by HIT antibodies in the absence of heparin. Heparin-independent platelet activation was attenuated when SRA-positive specimens were retested after platelets were incubated 45 minutes at 37 degrees C. Surface PF4 expression was diminished on the rested platelets, compared to the same platelets labeled immediately after handling. Thus compared to rested platelets, mildly activated platelets had elevated surface PF4 expression and a higher level of HIT antibody-mediated, heparin-independent platelet activation.

CONCLUSION

Surface expression of PF4 reflects HIT antigen presentation, and varies with the physiological state of platelets. Thus there can be differences in HIT antibody target availability among patients which may explain the variability in consequences of HIT antibody seropositivity.

An Overview of Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse drug reaction to heparin products leading to a prothrombotic state. Devastating clinical sequelae may result, including venous or arterial thromboembolism, limb amputation, and death. Heparin cessation alone is insufficient to manage HIT. Pharmacotherapy with argatroban or lepirudin is essential. This article reviews the pathogenesis, diagnosis, and pharmacotherapy of HIT.

A fatal case of heparin-induced thrombocytopenia and thrombosis

Heparin induced thrombocytopenia (HIT) is a significant, potentially life-threatening immune-mediated adverse event that occurs several days after commencement of therapy with unfractionated or low-molecular weight heparin. We present a 51-year-old female treated with unfractionated heparin for acute deep venous thrombosis (DVT) and pulmonary embolism (PE). She developed extension of her thrombosis and was promptly diagnosed with heparin-induced thrombocytopenia and thrombosis (HITT). She did not, however, develop thrombocytopenia until 5 days after the extension of her thrombosis. The possible diagnosis of HITT is important for clinicians to keep in mind for all patients that are receiving any form of heparin, not only those patients who present with thrombocytopenia but also those with otherwise unexplainable thrombosis regardless of the platelet count.

Thrombocytopenia and other hot topics

A frequent issue in the management of cancer patients with thrombosis is thrombocytopenia, whether related to chemotherapy, heparin, or other drugs. The oncologist will have multiple new anticoagulants to choose from in the future, but for now, the effect of these experimental agents on cancer thrombosis is unknown. Despite the effectiveness of anticoagulation in cancer patients, survival benefit remains controversial. Given the ongoing clinical questions and new drugs, anticoagulant therapy in patients with cancer promises to have an exciting future.

Heparin-induced Thrombocytopenia: Pathophysiology, Diagnosis, and Review of Pharmacotherapy

Heparin-induced thrombocytopenia is an adverse drug reaction to heparin therapy leading to devastating clinical outcomes including venous thromboembolism, myocardial infarction, stroke, and limb amputation. Heparin cessation alone is not sufficient for the management of heparin-induced thrombocytopenia. Direct thrombin inhibitors, such as argatroban and lepirudin, are considered the mainstay for the management of heparin-induced thrombocytopenia. Case reports support the use of fondaparinux in the management of heparin-induced thrombocytopenia; however, randomized trials are still lacking. This article will review the pathophysiology, clinical presentation, complications, diagnosis, and pharmacotherapy management of heparin-induced thrombocytopenia.

Thrombocytopenia after total knee arthroplasty

Heparin-induced thrombocytopenia is a serious complication during antithromboembolic prophylaxis caused by anti-heparin/platelet factor 4 (PF4) complex antibodies. It typically arises 3 to 15 days after the beginning of therapy and may result in an increased risk of arterial and venous thromboembolism. This article presents a case of thrombocytopenia associated with vein thrombosis in a man who underwent a total knee arthroplasty (TKA).

Heparin-Induced Thrombocytopenia With Thrombosis After Endovascular Aneurysm Repair

Heparin-induced thrombocytopenia is an immune-mediated syndrome that results from unfractionated heparin or low molecular weight heparin exposure. It often remains unrecognized and undertreated and can cause limb and/or life-threatening thrombosis. The authors present 2 cases of thrombosis: one arterial and the other venous that occurred following endovascular abdominal aortic aneurysm repair. To the authors' knowledge, this is only the second report of arterial thrombosis and the first of deep vein thrombosis as a result of heparin-induced thrombocytopenia developing following endovascular abdominal aortic aneurysm repair. This underscores the importance of considering heparin-induced thrombocytopenia as a potential cause for postendovascular thrombotic complications in the patient who develops thrombocytopenia following this procedure.

Platelet factor 4/heparin antibody (IgG/M/A) in healthy subjects: a literature analysis of commercial immunoassay results

PURPOSE

We determined the seroprevalence of platelet factor 4 (PF4)/heparin antibodies in healthy subjects.

METHODS

A literature search identified studies in which healthy subjects were evaluated using commercial immunoassays for PF4/heparin antibody (IgG/M/A). Proportions of test-positive subjects were calculated, by assay.

RESULTS

Across 11 eligible studies, 860 healthy subjects were tested using the Stago enzyme-linked immunosorbent assay (ELISA) (nine studies), GTI ELISA (three studies), and/or DiaMed particle gel immunoassay (PGIA) (three studies). Seropositivity occurred in 17 of 790 (2.2%, 95% CI, 1.1-3.2%) subjects by Stago ELISA, one of 100 (1.0%, 95% CI, 0-3.0%) subjects by GTI ELISA, and three of 70 (4.3%, 95% CI, 0-9.0%) subjects by PGIA (P > 0.20). Of seven seropositive subjects tested further, none had platelet-activating antibodies.

CONCLUSION

Commercial immunoassays detect PF4/heparin antibody in 1.0-4.3% of healthy subjects. Because this "background" prevalence overlaps seropositivity rates in heparin-treated patients in various clinical settings, normality cut-offs may require refinement.