Incidence of thrombocytopenia in hospitalized patients with venous thromboembolism

Trends in Initial Anticoagulation Among US Patients Hospitalized With Acute Pulmonary Embolism 2011-2020

STUDY OBJECTIVE

Guidelines recommend low-molecular-weight heparin (LMWH) and direct oral anticoagulants (DOACs) rather than unfractionated heparin (UFH) for treatment of acute pulmonary embolism (PE) given their efficacy and reduced risk of bleeding. Using data from a large consortium of US hospitals, we examined trends in initial anticoagulation among hospitalized patients diagnosed with acute PE.

METHODS

We conducted a retrospective study of inpatient and observation cases between January 1, 2011, and December 31, 2020, among individuals aged more than or equal to 18 years treated at acute care hospitals contributing data to the Premier Healthcare Database. Included cases received a diagnosis of acute PE, underwent imaging for PE, and received anticoagulation at the time of admission. The primary outcome was the initial anticoagulant selected for treatment.

RESULTS

Among 299,016 cases at 1,045 hospitals, similar proportions received initial treatment with UFH (47.4%) and LMWH (47.9%). Between 2011 and 2020, the proportion of patients initially treated with UFH increased from 41.9% to 56.3%. Over this period, use of LMWH as the initial anticoagulant was reduced from 58.1% in 2011 to 37.3% in 2020. The proportion of cases admitted to the ICU, treated with mechanical ventilation or vasopressors, and inpatient mortality were stable. Factors most strongly associated with receipt of UFH were admission to the ICU (odds ratio [OR] 6.90; 95% confidence interval [CI] 6.31 to 7.54) or step-down unit (OR 2.30; 95% CI 2.16 to 2.45), receipt of thrombolysis (OR 4.25; 95% CI 3.09 to 5.84) or vasopressors (OR 1.83; 95% CI 1.32 to 2.54), and chronic renal disease (OR 1.67; 95% CI 1.54 to 1.81).

CONCLUSIONS

Despite recommendations that LMWH and DOACs be considered first-line for most patients with acute PE, use of UFH is common and increasing. Further research is needed to elucidate factors associated with persistent use of UFH and opportunities for deimplementation of low-value care.

Association of medical comorbidities in obese subjects diagnosed with heparin-induced thrombocytopenia

Objectives

Heparin-induced thrombocytopenia can occur in obese subjects. The medical comorbidities associated with obesity may contribute to the pathogenesis of this disease. It is unknown, however, which specific medical comorbidities and if higher odds of thrombosis are present in obese heparin-induced thrombocytopenia patients. We sought to determine whether obese heparin-induced thrombocytopenia subjects had higher odds of both comorbidities and thrombosis, hypothesizing that this patient population would have higher odds of both these conditions.

Methods

This was a multi-center retrospective study utilizing TriNetX©, an electronic health record database, in subjects aged 18-99 years diagnosed with heparin-induced thrombocytopenia. The cohort was divided into two groups (1) non-obese (body mass index < 30 kg/m2) and (2) obese (body mass index ⩾ 30 kg/m2). We evaluated patient characteristics, diagnostic, laboratory, medication, and procedure codes.

Results

A total of 1583 subjects (696 (44.0%) non-obese and 887 (56.0%) obese) were included. Obese subjects had higher odds of diabetes with complications (OR = 1.73, 95% CI = 1.35-2.22, p < 0.001) and without complications (OR = 1.81, 95% CI = 1.47-2.22, p < 0.001). This association was still present after correcting for demographic and clinical factors. There were no increased odds of thrombosis observed in the obesity group.

Conclusions

Our study found that obese heparin-induced thrombocytopenia subjects had higher odds of having a diabetes mellitus comorbidity, but did not have higher odds of thrombosis. Given obesity is considered a hypercoagulable state, further study may be needed to understand why obese subjects diagnosed with heparin-induced thrombocytopenia do not have higher rates of thrombosis.

Intermediate-Risk and High-Risk Pulmonary Embolism: Recognition and Management: Cardiology Clinics: Cardiac Emergencies

Pulmonary embolism (PE) is the third most common cause of cardiovascular death. Every specialty of medical practitioner will encounter PE in their patients, and should be prepared to employ contemporary strategies for diagnosis and initial risk-stratification. Treatment of PE is based on risk-stratification, with anticoagulation for all patients, and advanced modalities including systemic thrombolysis, catheter-directed therapies, and mechanical circulatory supports utilized in a manner paralleling PE severity and clinical context.

In-hospital mortality of heparin-induced thrombocytopenia in end-stage kidney disease. A retrospective national population-based cohort study

AIM

Heparin induced thrombocytopenia (HIT) and end stage kidney disease (ESKD) are independent conditions associated with increased mortality and morbidity, however, whether ESKD is an independent risk factor for increased mortality in HIT admissions is not well studied. Therefore, we aimed to compare in-hospital mortality in HIT admissions based on their ESKD status.

METHODS

This is a retrospective cohort study of HIT hospitalizations aged 18 and older using the 2016-2019 national inpatient sample (NIS) database.

RESULTS

From 2016 to 2019 we had 12 161 admissions for HIT among 28 484 087 total hospitalizations. The annual incidence rate for HIT admissions per 100 000 admissions were: 47, 46, 41.1, and 36.6, respectively (p < .001) in 2016, 2017, 2018, and 2019 respectively. Among HIT admissions, the mean age was 64.3 years, 46.8% were females, 68% were Whites and 16% were Blacks. Black patients have a significantly higher likelihood of in-hospital mortality than White patients (aOR 1.25; 95% CI: 1.06, 1.48; p = .007). Patients who did not have any insurance or self-pay had higher mortality compared to Medicare (aOR 1.64; 95% CI: 1.13, 2.38; p = .009). ESKD status was not associated with higher or lower in-hospital mortality among HIT admissions (aOR 1.002; 95% CI: 0.84, 1.19; p = .981) after adjusting for age, sex, race, and insurance status.

CONCLUSION

There are no higher or lower odds of in-hospital mortality in the ESKD subgroup in HIT admissions in adults. Decreasing incidence of HIT hospitalizations was seen over the years from 2016 to 2019.

Elucidation of Cellular Contributions to Heparin-Induced Thrombocytopenia Using Omic Approaches

Heparin-induced thrombocytopenia (HIT) is an unpredictable, complex, immune-mediated adverse drug reaction associated with a high mortality. Despite decades of research into HIT, fundamental knowledge gaps persist regarding HIT likely due to the complex and unusual nature of the HIT immune response. Such knowledge gaps include the identity of a HIT immunogen, the intrinsic roles of various cell types and their interactions, and the molecular basis that distinguishes pathogenic and non-pathogenic PF4/heparin antibodies. While a key feature of HIT, thrombocytopenia, implicates platelets as a seminal cell fragment in HIT pathogenesis, strong evidence exists for critical roles of multiple cell types. The rise in omic technologies over the last decade has resulted in a number of agnostic, whole system approaches for biological research that may be especially informative for complex phenotypes. Applying multi-omics techniques to HIT has the potential to bring new insights into HIT pathophysiology and identify biomarkers with clinical utility. In this review, we review the clinical, immunological, and molecular features of HIT with emphasis on key cell types and their roles. We then address the applicability of several omic techniques underutilized in HIT, which have the potential to fill knowledge gaps related to HIT biology.

Venous Thromboembolism for the Practicing Cardiologist

Venous thromboembolism (VTE), encompassing pulmonary embolism (PE) and deep vein thrombosis (DVT), is encountered commonly. Acute PE may present as a high-risk cardiovascular emergency, and acute DVT can cause acute and chronic vascular complications. The goal of this review is to ensure that cardiologists are comfortable managing VTE-including risk stratification, anticoagulation therapy, and familiarity with primary reperfusion therapy. Clinical assessment and determination of degree of right ventricular dysfunction are critical in initial risk stratification of PE and determination of parenteral versus oral anticoagulation therapy. Direct oral anticoagulants have emerged as preferred first-line oral anticoagulation strategy in VTE scenarios.

Platelet factor 4 polyanion immune complexes: heparin induced thrombocytopenia and vaccine-induced immune thrombotic thrombocytopenia

BACKGROUND

This is a review article on heparin-induced thrombocytopenia, an adverse effect of heparin therapy, and vaccine-induced immune thrombotic thrombocytopenia, occurring in some patients administered certain coronavirus vaccines.

MAIN BODY/TEXT

Immune-mediated thrombocytopenia occurs when specific antibodies bind to platelet factor 4 /heparin complexes. Platelet factor 4 is a naturally occurring chemokine, and under certain conditions, may complex with negatively charged molecules and polyanions, including heparin. The antibody-platelet factor 4/heparin complex may lead to platelet activation, accompanied by other cascading reactions, resulting in cerebral sinus thrombosis, deep vein thrombosis, lower limb arterial thrombosis, myocardial infarction, pulmonary embolism, skin necrosis, and thrombotic stroke. If untreated, heparin-induced thrombocytopenia can be life threatening. In parallel, rare incidents of spontaneous vaccine-induced immune thrombotic thrombocytopenia can also occur in some patients administered certain coronavirus vaccines. The role of platelet factor 4 in vaccine-induced thrombosis with thrombocytopenia syndrome further reinforces the importance the platelet factor 4/polyanion immune complexes and the complications that this might pose to susceptible individuals. These findings demonstrate, how auxiliary factors can complicate heparin therapy and drug development. An increasing interest in biomanufacturing heparins from non-animal sources has driven a growing interest in understanding the biology of immune-mediated heparin-induced thrombocytopenia, and therefore, the development of safe and effective biosynthetic heparins.

SHORT CONCLUSION

In conclusion, these findings further reinforce the importance of the binding of platelet factor 4 with known and unknown polyanions, and the complications that these might pose to susceptible patients. In parallel, these findings also demonstrate how auxiliary factors can complicate the heparin drug development.

A patient with pulmonary embolism takes a surprising HIT: a case report

Background

Venous thromboembolism (VTE) is a common condition that may manifest as intermediate or high-risk pulmonary embolism (PE), requiring either primary or subsequent fibrinolytic therapy. In these cases, catheter-directed thrombolysis (CDT) has been shown to be beneficial.

Case summary

We present the case of a borderline obese but otherwise healthy 43-year-old male individual, who was admitted with acute intermediate- to high-risk PE requiring treatment with intravenous unfractionated heparin. After initial therapy failure, the patient received CDT, with subsequent clinical worsening, and a mixed result of imaging studies suggesting partial central worsening and partial peripheral improvement of the thrombotic burden and right ventricular (RV) function. After a multidisciplinary PE response team (PERT) consultation, the diagnosis of heparin-induced thrombocytopenia (HIT) with normal platelet levels was made. Therapy was changed to intravenous bivalirudin, with an excellent clinical response and complete recovery of RV function. The patient was discharged with oral rivaroxaban therapy, and on follow-up was otherwise well.

Discussion

Apparent failure of thrombolytic therapy for VTE warrants a clinical investigation into possible causes of a pro-thrombotic state. In this case, the diagnosis of HIT was surprising, especially due to only a mild decline in platelet levels that were well within normal range. We also acknowledge the significance of our PERT in the key diagnosis made in this case.

Quantitative and Qualitative Platelet Derangements in Cardiac Surgery and Extracorporeal Life Support

Thrombocytopenia and impaired platelet function are known as intrinsic drawbacks of cardiac surgery and extracorporeal life supports (ECLS). A number of different factors influence platelet count and function including the inflammatory response to a cardiopulmonary bypass (CPB) or to ECLS, hemodilution, hypothermia, mechanical damage and preoperative treatment with platelet-inhibiting agents. Moreover, although underestimated, heparin-induced thrombocytopenia is still a hiccup in the perioperative management of cardiac surgical and, above all, ECLS patients. Moreover, recent investigations have highlighted how platelet disorders also affect patients undergoing biological prosthesis implantation. Though many hypotheses have been suggested, the mechanism underlying thrombocytopenia and platelet disorders is still to be cleared. This narrative review aims to offer clinicians a summary of their major causes in the cardiac surgery setting.

Positive Heparin/PF4 Antibodies and High Mortality Rate: a Retrospective Case-Series Analysis

Introduction

Heparin-induced thrombocytopenia (HIT) is a potentially lethal complication of unfractionated or low-molecular weight heparin therapy. We aimed to determine the incidence and mortality rate of patients with positive heparin/platelet factor 4 (PF4) antibodies, which is a rapid detection test of HIT.

Methods

Coronary artery bypass grafting and mitral and aortic valve surgeries were evaluated. Cardiopulmonary bypass was employed in all patients. The diagnosis of HIT was based on immunological assays. Postoperative complications, mortality rates, and the causes of death were specified in patients with positive heparin/PF4 antibodies.

Results

Postoperative thrombocytopenia was detected in 257 patients. Twenty of these patients undergoing open heart surgery were included in the final analysis. Antibodies against heparin/PF4 complex were positive in 20 patients. The mean body mass index was 28.8±2.3 kg/m², mean value of left ventricular ejection fraction was 48.3±6.7%, cardiopulmonary bypass time was 113.0±35.0 min, aortic cross-clamping time was 88.0±32.7 min, mean intensive care unit length of stay was 10.9±4.9 days, mean preoperative platelet count was 307.250±88528 platelets/microliter, and mean postoperative platelet count was 243.050±89.354 platelets/microliter. The mean duration of heparin exposure was 6.9±2.9 days. The mortality rate was 45% (nine patients) and 1.2% (three patients) in heparin/PF4 complex positive and negative patients, respectively.

Conclusion

Although the incidence of HIT was low in patients undergoing open heart surgery, an increased rate of early mortality was observed in patients with positive heparin/PF4 antibodies.

Heparin-induced Thrombocytopenia: Pathophysiology, Diagnosis and Management

Heparin-induced thrombocytopenia (HIT), even rare, is a life-threatening, immune-mediated complication of heparin exposure. It is considered the most severe non-bleeding adverse reaction of heparin treatment and one of the most important adverse drug reactions. The pathophysiological basis of HIT results from the formation of an immunocomplex consisting of an auto-antibody against platelet factor 4 (PF4) - heparin complex, which binds to the surface of platelets and monocytes, provoking their activation by cross-linking FcgIIA receptors. Platelets and monocyte activation, leads to the generation of catastrophic arterial and venous thrombosis, with a mortality rate of 20%, without early recognition. The definitive diagnosis of HIT i.e., clinical and laboratory evidence, can not be done at the onset of symptoms because laboratory results may not be available for several days. Thus, the initial approach is to predict the likelihood of HIT, because in highly suspected patients immediate heparin cessation and initiation of alternative anticoagulation treatment are crucial for the prevention of the devastating thrombotic sequelae. Herein, we describe the pathophysiology, the clinical manifestations, the diagnostic approach, and the management of patients with HIT.

Heparin-induced thrombocytopenia and acute colonic pseudo-obstruction after therapeutic anticoagulation in a very elderly patient with hip fracture: a case report

BACKGROUND

Hip fractures have become a severe public health problem, especially in very elderly patients. Most of them are treated with low molecular weight heparin as prophylaxis or treatment of venous thromboembolism. Heparin-induced thrombocytopenia is one of the complications induced by low molecular weight heparin, which may cause poor prognosis. However, there is not enough awareness for heparin-induced thrombocytopenia in very elderly trauma patients.

CASE PRESENTATION

We report a case of hip fracture with heparin-induced thrombocytopenia in a very elderly patient. The patient developed heparin-induced thrombocytopenia, digestive hemorrhage and acute colonic pseudo-obstruction after the use of low molecular weight heparin, which eventually led to death.

CONCLUSIONS

This is the first case report of digestive hemorrhage and acute colonic pseudo-obstruction in heparin-induced thrombocytopenia patients with major trauma. This case highlights the severity of HIT in very elderly patients with hip fractures using low molecular weight heparin, and the need for platelet monitoring in these patients. We indicate that there may be a correlation of pathogenesis between digestive hemorrhage and acute colonic pseudo-obstruction in heparin-induced thrombocytopenia patients.

Incidence and outcomes of heparin-induced thrombocytopenia in solid malignancy: an analysis of the National Inpatient Sample Database

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse reaction to heparin products characterized by thrombocytopenia with or without thrombosis. This study aimed to determine the incidence, morbidity, mortality and economic burden of HIT in solid-malignancy-related hospitalizations. We analyzed the National Inpatient Sample Database (NIS), the largest public database of hospital admissions in the United States, from January 2012 to September 2015. The primary outcome of the study was the incidence of HIT. Secondary outcomes included incidence of venous thrombosis (acute deep venous thrombosis and pulmonary embolism), arterial thrombosis (thrombotic stroke, myocardial infarctions and other arterial thromboembolism), mortality associated with HIT, length of stay, total hospital charges and disposition. During the study period, 7 437 049 hospitalizations had an associated diagnosis of solid malignancy. Approximately 0·08% (n = 6225) hospitalizations had a secondary diagnosis of HIT in this population. The standardized incidence of total thrombotic events was higher in the solid malignancy with HIT compared to the solid malignancy without HIT group (24·7% vs. 6·8%, P < 0·001). The standardized mortality rate was 4·8% in solid malignancy with HIT compared to 3·4% in the without HIT group (OR, 1·53; 95% CI, 1·25-1·89; P < 0·001). HIT in solid malignancy is a rare condition but associated with increased morbidity and mortality.

Surgical embolectomy for acute massive pulmonary embolism: state of the art

Massive pulmonary embolism (PE) is a severe condition that can potentially lead to death caused by right ventricular (RV) failure and the consequent cardiogenic shock. Despite the fact thrombolysis is often administrated to critical patients to increase pulmonary perfusion and to reduce RV afterload, surgical treatment represents another valid option in case of failure or contraindications to thrombolytic therapy. Correct risk stratification and multidisciplinary proactive teams are critical factors to dramatically decrease the mortality of this global health burden. In fact, the worldwide incidence of PE is 60-70 per 100,000, with a mortality ranging from 1% for small PE to 65% for massive PE. This review provides an overview of the diagnosis and management of this highly lethal pathology, with a focus on the surgical approaches at the state of the art.

Comparative Analysis of the Suspected Heparin-Induced Thrombocytopenia Level in Korea

The primary objective of our study was to evaluate the frequency of suspected heparin-induced thrombocytopenia (HIT) among patients treated with different formulations of heparin and investigate the factors that affect the incidence of HIT. This study is an electronic medical record (EMR)-based large-scale retrospective cohort study conducted from 2009 to 2014 in Korea. After hospitalization, patient platelet count was determined before heparin was prescribed, and all platelet count values obtained during hospitalization were extracted. Suspected HIT was estimated by three 4Ts scores (acute thrombocytopenia, timing onset and other possible causes), which when combined yielded a high probability of HIT. Among 6046 patients enrolled in this study, HIT was suspected in 641 cases (10.6%) and a statistically significant increase in HIT incidence rate was observed for three heparins used (p < 0.001). Dalteparin (HR = 0.55, p = 0.036) and enoxaparin (HR = 0.40, p < 0.001) showed a relatively low HIT incidence rate, compared to unfractionated heparin. Majority of suspected HIT cases (76.9 and 66.7%) occurred in days 8-10 and 5-7 of dalteparin and enoxaparin treatments, respectively. Most of the patients medicated with dalteparin were cancer patients; however, no statistically significant relationship was observed between HIT occurrence and cancer. HIT can cause serious complications, making early diagnosis crucial. Clinical practitioners first prescribing heparin should focus on preventing and detecting complications early by conducting frequent, regular platelet counts before and after heparin administration.

Determinants of treatment duration in the prevention of recurrent venous thromboembolism: a protocol for a balanced vignette experiment

INTRODUCTION

Venous thromboembolism (VTE) is a condition that annually occurs in approximately 1‰ of the world's population. Patients who have already had a VTE are at elevated risk for a recurrent VTE. Recurrent events increase the risk of long-term sequelae and can be fatal. Adequate secondary prophylaxis is thus needed to prevent such events. Patients with VTE are often prone to bleeding, and pharmacological prophylaxis exacerbates bleeding risk. Expert opinions on the optimum duration of secondary prophylaxis in VTE still vary substantially. The existence of treatment guidelines has not led to uniformity of VTE secondary prophylaxis strategies, which means that physicians still adhere to individual risk calculi in determining treatment duration.

METHODS AND ANALYSIS

The aim of this study is to establish what factors lie at the root of this variance in VTE secondary prophylactic treatment strategies, and what risk factors are deemed of particular importance in determining the perceived risks and benefits of variable treatment durations. To do this, we created a survey based on a D-efficient and G-efficient balanced experimental vignette design. This protocol covers all aspects of how this survey was set up and how it was implemented. The analysis of the experimental data will be carried out using mixed-effects methods, which are beneficial in scenarios with high interindividual variance and correlated (eg, repeated-measures) responses. We propose the use of maximal random effects structures insofar as possible.

ETHICS AND DISSEMINATION

All data are de-identified, and any identifying characteristics of the respondents will not be reported in a final manuscript or elsewhere. A paper describing the expert interviews is currently under peer review. A manuscript that contains the analysis of the results of the experiment described in this protocol is being drafted, and will also be submitted to a peer-reviewed journal.

Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an immune complication of heparin therapy caused by antibodies to complexes of platelet factor 4 (PF4) and heparin. Pathogenic antibodies to PF4/heparin bind and activate cellular FcγRIIA on platelets and monocytes to propagate a hypercoagulable state culminating in life-threatening thrombosis. It is now recognized that anti-PF4/heparin antibodies develop commonly after heparin exposure, but only a subset of sensitized patients progress to life-threatening complications of thrombocytopenia and thrombosis. Recent scientific developments have clarified mechanisms underlying PF4/heparin immunogenicity, disease susceptibility, and clinical manifestations of disease. Insights from clinical and laboratory findings have also been recently harnessed for disease prevention. This review will summarize our current understanding of HIT by reviewing pathogenesis, essential clinical and laboratory features, and management.

Diagnosis and management of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder caused by antibodies to platelet factor 4/heparin (PF4/H) complexes. It presents with declining platelet counts 5 to 14 days after heparin administration and results in a predisposition to arterial and venous thrombosis. Establishing the diagnosis of HIT can be extremely challenging. It is essential to conduct a thorough clinical evaluation in addition to laboratory testing to confirm the presence of PF4/H antibodies. Multiple clinical algorithms have been developed to aid the clinician in predicting the likelihood of HIT. Once HIT is recognized, an alternative anticoagulant should be initiated to prevent further complications.

Systematic review on heparin-induced thrombocytopenia in children: a call to action

BACKGROUND

Heparin-induced thrombocytopenia (HIT) has increasingly been reported in children as an indication for use of new alternative anticoagulant drugs (NAADs).

OBJECTIVES

To systematically review the literature regarding: (i) the incidence and prevalence of seroconversion and HIT and (ii) the clinical/laboratory findings and management of HIT in children.

DESIGN/METHODS

MEDLINE and EMBASE databases were searched for studies that reported pediatric cases of HIT. Methodological reliability assessment of studies was performed with the Loney scale.

RESULTS

The incidence of seroconversion in neonates ranged between 0% and 1.7%. There were no cases of neonatal HIT in the included cohorts. The incidence range of seroconversion in the non-neonatal population was 1.3-52%. The incidence of HIT in non-neonates after cardiopulmonary bypass was 0.33% (95%CI, < 0.01-2.04). Whereas more than half of pediatric cases labeled as HIT (30/52) did not include pivotal features of this syndrome, 80% of them received NAADs.

CONCLUSION

The incidence of HIT is likely to have been overestimated in children, leading to potential misuse of NAADs in many cases. Clinical findings and laboratory assessment of pediatric cases are poorly described in the literature at present. Thorough laboratory investigation, proper reporting of cases and adequate design of studies are mandatory to elucidate the clinical/laboratory picture of pediatric HIT.

Lower limb gangrene postcardiac surgery

A 67-year-old gentleman presented with a 1-day history of left foot pain. He had recently been discharged following a coronary artery bypass graft; during the admission, he had received an intravenous heparin infusion. Examination revealed black-purple discolouration of the first and second digits of the left foot with pitting oedema to the level of the knee. The posterior tibial and dorsalis pedis pulses were both shown to be patent. A new thrombocytopenia was noted. Ultrasound imaging revealed multiple deep vein thrombosis. The history of recent heparin exposure coupled with venous gangrene secondary to deep vein thrombosis was consistent with heparin-induced thrombocytopenia. He was treated acutely with intravenous danaparoid and later with warfarin. There was complete resolution of the venous gangrene at 1 month follow-up.

Heparin-induced thrombocytopenia following hip and knee arthroplasty

Until recently, both the British Society for Haematology and American College of Chest Physicians recommended platelet monitoring in all surgical patients receiving prophylactic low molecular weight heparin (LMWH) for the early diagnosis of heparin-induced thrombocytopenia (HIT). These guidelines were reversed in 2012 based upon an analysis considering resource expenditure, assay result timeframes, and complications relating to HIT treatment. However, there are no large studies reviewing lower limb arthroplasty patients on an individual basis to determine the incidence of HIT in this patient group. This study investigated 10 797 patients who underwent primary hip or knee arthroplasty with LMWH prophylaxis over a 5 years period. 32·6% of patients (n = 3515) had platelet counts recorded up to 14 d postoperatively with 13 patients (0·37%) developing thrombocytopenia. Platelet counts recovered spontaneously in five patients, and two patients had other identifiable causes. Only one of the remaining six patients developed thrombosis indicating an incidence of HIT-related thrombosis of 0·03%. The potential for identifying HIT with platelet monitoring in patients receiving LMWH prophylaxis is low and therefore routine monitoring for HIT is not justified.

Treatment and prevention of heparin-induced thrombocytopenia: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an antibody-mediated adverse drug reaction that can lead to devastating thromboembolic complications, including pulmonary embolism, ischemic limb necrosis necessitating limb amputation, acute myocardial infarction, and stroke.

METHODS

The methods of this guideline follow the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

Among the key recommendations for this article are the following: For patients receiving heparin in whom clinicians consider the risk of HIT to be > 1%, we suggest that platelet count monitoring be performed every 2 or 3 days from day 4 to day 14 (or until heparin is stopped, whichever occurs first) (Grade 2C). For patients receiving heparin in whom clinicians consider the risk of HIT to be < 1%, we suggest that platelet counts not be monitored (Grade 2C). In patients with HIT with thrombosis (HITT) or isolated HIT who have normal renal function, we suggest the use of argatroban or lepirudin or danaparoid over other nonheparin anticoagulants (Grade 2C). In patients with HITT and renal insufficiency, we suggest the use of argatroban over other nonheparin anticoagulants (Grade 2C). In patients with acute HIT or subacute HIT who require urgent cardiac surgery, we suggest the use of bivalirudin over other nonheparin anticoagulants or heparin plus antiplatelet agents (Grade 2C).

CONCLUSIONS

Further studies evaluating the role of fondaparinux and the new oral anticoagulants in the treatment of HIT are needed.

Heparin induced thrombocytopenia: case presentation and review

Heparin Induced Thrombocytopenia (HIT) is an adverse effect of heparin therapy with possibly devastating consequences. We present a case of HIT Type II. An in-depth review of HIT is presented, examining the important clinical symptoms and diagnostic indicators. The treatment of HIT is then discussed, with an emphasis on current therapies. An extensive literature review has been performed to present a comprehensive review of the causes, pathophysiology and treatment of HIT.

How I treat heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia is a prothrombotic adverse drug effect induced by platelet-activating antibodies against multimolecular complexes of platelet factor 4 and heparin. Diagnosis rests on a clinical assessment of disease probability and laboratory testing. Management involves immediate discontinuation of heparin and initiation of an alternative anticoagulant. Because of the frequency of thrombocytopenia among heparinized patients, the limited specificity of widely available immunoassays, the limited availability of more specific functional assays, and clinicians' fears of missing a case of true disease, overtesting, overdiagnosis, and overtreatment have become common. As a result, a substantial number of thrombocytopenic patients are unnecessarily exposed to costly alternative anticoagulants and their attendant risk of bleeding. In this review, we describe not only our approach to the evaluation and management of patients with heparin-induced thrombocytopenia, but also the measures we use to minimize misdiagnosis and unnecessary treatment of patients without the disease. In addition, we propose areas of investigation for improvement of the diagnosis and management of this potentially fatal disorder.

Adverse effects of heparin

All the adverse effects of heparins are related to their wide variety of biological activities, with bleeding being the most important safety issue, resulting directly from the potency of heparin as an anticoagulant. However, it is hard to define the bleeding risk, since it depends on numerous parameters including the indication, dosage, method, and duration of heparin application, the clinical study design and definition of bleeding as well as patient characteristics and determinants of bleeding such as type of surgery and co-medication. Nonbleeding complications of heparins are caused by binding of heparin molecules to proteins other than antithrombin and to cells, which is generally more pronounced with unfractionated heparin than with low-molecular-weight heparins. Accordingly, heparin-induced thrombocytopenia, the most severe nonbleeding adverse reaction, occurs about 10 times less with low-molecular-weight heparins than with unfractionated heparin. Frequent and therefore important adverse reactions of heparins are skin lesions resulting from delayed-type hypersensitivity reactions. All the other undesirable effects are discussed as well, but they are mostly clinically irrelevant.

Recent advances in heparin-induced thrombocytopenia

PURPOSE OF REVIEW

Heparin-induced thrombocytopenia (HIT) is a prothrombotic complication of heparin therapy caused by antibodies against platelet factor 4/heparin complexes. Progress in our understanding of HIT has translated to improvements in treatment and patient outcomes. The objective of this review is to examine recent advances and highlight areas of future inquiry in the epidemiology, diagnosis, and management of this potentially fatal disorder.

RECENT FINDINGS

Risk factors for the development of HIT related to heparin administration are well described. Recent identification of host-related risk factors adds to our understanding of disease epidemiology. The limited specificity of clinical diagnosis and widely used immunologic assays for HIT results in frequent overdiagnosis. Novel clinical decision rules and laboratory assays to improve diagnosis are in development. Fondaparinux, bivalirudin, and desirudin have recently been added to the HIT armamentarium.

SUMMARY

Despite these advances, critical issues remain to be addressed. Future research efforts will focus on the identification of novel clinical risk factors and biomarkers that will enable recognition of individuals at greatest risk, optimization of diagnostic strategies and use of currently available therapeutics, and development of new drugs that not only reduce thrombotic complications, but also minimize bleeding risk, are well tolerated in patients with organ dysfunction, and facilitate transition to outpatient therapy.

Heparin-associated thrombocytopenia in 24,401 patients with venous thromboembolism: findings from the RIETE Registry

BACKGROUND

Whether the treatment of venous thromboembolism (VTE) with unfractionated heparin (UFH) confers a higher risk of thrombocytopenia than does treatment with low molecular weight heparin (LMWH) remains controversial, and very few data are available from routine clinical practice.

OBJECTIVES

We assessed the incidence, risk factors and prognosis of heparin-associated thrombocytopenia (HAT) according to the type of heparin therapy, UFH or LMWH.

PATIENTS/METHODS

Data were obtained from the international prospective Registro Informatizado de la Enfermedad TromboEmbolica venosa (RIETE), which included 25,369 patients with confirmed VTE until February 2009. Among them, 24,401 patients were treated either with UFH or with LMWH, and had available information about the 6-month occurrence of confirmed thrombocytopenia, defined as a platelet count ≤ 150,000 mm(-3) .

RESULTS

One hundred and forty-one patients receiving UFH and/or LMWH developed thrombocytopenia within a 6-month period. The incidence of HAT was significantly higher in the UFH group (1.36%, 95% confidence interval [CI] 0.79-2.17) than in the LMWH group (0.54%, 95% CI 0.44-0.64). As compared with LMWH, UFH significantly increased the risk of HAT in female patients (adjusted hazard ratio [HR] 4.90%, 95% CI 2.58-9.31, P = 0.001) but not in male patients (adjusted HR 1.60%, 95% CI 0.64-3.97, P = 0.31); P = 0.027 for comparison. In each gender, the UFH-associated excess risk was confined to patients with VTE unrelated to cancer. The poor prognosis of patients with thrombocytopenia was not influenced by the type of heparin therapy.

CONCLUSIONS

In routine clinical practice, treatment of VTE with UFH seems to confer a higher risk of thrombocytopenia than does treatment with LMWH, especially in women and non-cancerous patients.