Heparin-induced thrombocytopenia

Translating proof-of-concept for platelet slip into improved antithrombotic therapeutic regimens

Platelets are central to thrombosis. Research at the intersection of biological and physical sciences provides proof-of-concept for shear rate-dependent platelet slip at vascular stenosis and near device surfaces. Platelet slip extends the observed biological "slip-bonds" to the boundary of functional gliding without contact. As a result, there is diminished engagement of the coagulation cascade by platelets at these surfaces. Comprehending platelet slip would more precisely direct antithrombotic regimens for different shear environments, including for percutaneous coronary intervention (PCI). In this brief report we promote translation of the proof-of-concept for platelet slip into improved antithrombotic regimens by: (1) reviewing new supporting basic biological science and clinical research for platelet slip; (2) hypothesizing the principal variables that affect platelet slip; (3) applying the consequent construct model in support of-and in some cases to challenge-relevant contemporary guidelines and their foundations (including for urgent, higher-risk PCI); and (4) suggesting future research pathways (both basic and clinical). Should future research demonstrate, explain and control platelet slip, then a paradigm shift for choosing and recommending antithrombotic regimens based on predicted shear rate should follow. Improved clinical outcomes with decreased complications accompanying this paradigm shift for higher-risk PCI would also result in substantive cost savings.

Management of Heparin-Induced Thrombocytopenia: A Contemporary Review

Heparin-induced thrombocytopenia (HIT) is a life- and limb-threatening immune-mediated emergency classically associated with heparin therapy. This review focuses on type II HIT, characterized by the development of antibodies against platelet-factor 4 (PF4) bound to heparin after exposure, causing life-threatening thrombocytopenia, arterial thrombosis, and/or venous thrombosis. The high morbidity and mortality rates emphasize the need for early recognition and urgent intervention with discontinuation of heparin and initiation of non-heparin anticoagulation. We discuss the management of HIT with an emphasis on recent developments: (i) incorporating the phases of HIT (i.e., suspected, acute, subacute A and B, and remote) into its management, categorized according to platelet count, immunoassay, and functional assay results and (ii) direct-acting oral anticoagulants (DOACs), which are increasingly used in appropriate cases of acute HIT (off-label). In comparison to parenteral options (e.g., bivalirudin and danaparoid), they are easier to administer, are more cost-effective, and obviate the need for transition to an oral anticoagulant after platelet recovery. We also identify the knowledge gaps and suggest areas for future research.

The methods for removal of direct oral anticoagulants and heparins to improve the monitoring of hemostasis: a narrative literature review

The assessment of hemostasis is necessary to make suitable decisions on the management of patients with thrombotic disorders. In some clinical situations, for example, during thrombophilia screening, the presence of anticoagulants in sample makes diagnosis impossible. Various elimination methods may overcome anticoagulant interference. DOAC-Stop, DOAC-Remove and DOAC Filter are available methods to remove direct oral anticoagulants in diagnostic tests, although there are still reports on their incomplete efficacy in several assays. The new antidotes for direct oral anticoagulants - idarucizumab and andexanet alfa - could be potentially useful, but have their drawbacks. The necessity to remove heparins is also arising as heparin contamination from central venous catheter or therapy with heparin disturbs the appropriate hemostasis assessment. Heparinase and polybrene are already present in commercial reagents but a fully-effective neutralizer is still a challenge for researchers, thus promising candidates remain in the research phase.

Upregulation of Coagulation Factor VIII and Fibrinogen After Pulmonary Endarterectomy in Patients with Chronic Thromboembolic Pulmonary Hypertension

OBJECTIVES

Chronic thromboembolic pulmonary hypertension (CTEPH) is associated with thrombotic states including elevated coagulation factor VIII (FVIII). Pulmonary endarterectomy (PEA) is the main treatment for CTEPH, and efficient anticoagulation is essential to prevent thromboembolism recurrence after surgery. We aimed to characterize longitudinal changes in FVIII and other coagulation biomarkers after PEA.

METHODS

Coagulation biomarker levels were measured at baseline and up to 12 months after operation in 17 consecutive patients with PEA. Temporal patterns of coagulation biomarkers, and correlation of FVIII with other coagulation biomarkers, were analyzed.

RESULTS

Baseline FVIII levels were elevated in 71% of the patients (mean 216 ± 67 IU/dl). FVIII doubled 7 days after PEA, peaking at 471 ± 87 IU/dl, and gradually returned to respective baseline levels within 3 months. Postoperative fibrinogen levels were also elevated. Antithrombin decreased at 1 to 3 days, D-dimer increased at 1 to 4 weeks, and thrombocytosis was observed at 2 weeks.

CONCLUSIONS

FVIII is elevated in most patients with CTEPH. After PEA, early but transient elevation of FVIII and fibrinogen, and delayed reactive thrombocytosis, occurs, and warrants careful postoperative anticoagulation to prevent thromboembolism recurrence.

Ischemic Stroke Due to Heparin-induced Thrombocytopenia during Severe COVID-19 Infection

A 53-year-old woman with severe coronavirus disease 2019 (COVID-19) pneumonia was admitted and treated with intravenous unfractionated heparin for thromboprophylaxis under general anesthesia with mechanical ventilation. She developed right hemiparesis after hospitalization due to a large hemorrhagic infarction. Her platelet count decreased from 243,000/μL at administration to 121,000/μL. Anti-platelet factor 4-heparin antibody testing was positive according to a latex immunoturbidimetric assay. She was therefore diagnosed with heparin-induced thrombocytopenia. We immediately stopped the heparin and started argatroban; the platelet count recovered, and thrombosis did not relapse. Physicians should consider heparin-induced thrombocytopenia as a cause of ischemic stroke in patients with COVID-19 infection.

Breast cancer cell-based ELISA: a potential material for better detection of heparin-induced thrombocytopenia antibodies

Heparin-induced thrombocytopenia (HIT) is caused by newly formed platelet-activating antibodies against complexes formed between platelet factor 4 (PF4) and heparin (H). HIT can result in life-threatening complications; thus, early detection of HIT antibodies is crucial for the treatment of the disease. The enzyme-linked immune absorbance assay (ELISA) for the identification of HIT antibodies is widely used in many laboratories, but in general, this test provides only ∼50% accuracy while other methods show multiple limitations. Here, we developed a new cell-based ELISA to improve the detection of HIT antibodies. Instead of immobilizing PF4 or PF4/H complexes directly onto a plate as in the standard ELISA, we added the complexes on breast cancer cells, i.e., cell line MDA-MB-231, and applied the same protocol for antibody detection. Using confocal laser scanning microscopy and flow cytometry for the characterization of bound complexes, we identified two types of HIT-mimicked antibodies (KKO and 1E12), which were able to differentiate from the non-HIT antibody (RTO). PF4-treated MDA-MB-231 cells allowed binding of HIT-mimicked antibodies better than PF4/H complexes. With human sera, the cell-based ELISA allowed better differentiation of clinically relevant from non-clinically relevant HIT antibodies as compared with the standard ELISA. Our findings provide a potential approach that contributes to the development of better assays for the detection of HIT antibodies.

Clinical Characteristics and Pharmacological Management of COVID-19 Vaccine-Induced Immune Thrombotic Thrombocytopenia With Cerebral Venous Sinus Thrombosis: A Review

Importance

The COVID-19 pandemic saw one of the fastest developments of vaccines in an effort to combat an out-of-control pandemic. The 2 most common COVID-19 vaccine platforms currently in use, messenger RNA (mRNA) and adenovirus vector, were developed on the basis of previous research in use of this technology. Postauthorization surveillance of COVID-19 vaccines has identified safety signals, including unusual cases of thrombocytopenia with thrombosis reported in recipients of adenoviral vector vaccines. One of the devastating manifestations of this syndrome, termed vaccine-induced immune thrombotic thrombocytopenia (VITT), is cerebral venous sinus thrombosis (CVST). This review summarizes the current evidence and indications regarding biology, clinical characteristics, and pharmacological management of VITT with CVST.

Observations

VITT appears to be similar to heparin-induced thrombocytopenia (HIT), with both disorders associated with thrombocytopenia, thrombosis, and presence of autoantibodies to platelet factor 4 (PF4). Unlike VITT, HIT is triggered by recent exposure to heparin. Owing to similarities between these 2 conditions and lack of high-quality evidence, interim recommendations suggest avoiding heparin and heparin analogues in patients with VITT. Based on initial reports, female sex and age younger than 60 years were identified as possible risk factors for VITT. Treatment consists of therapeutic anticoagulation with nonheparin anticoagulants and prevention of formation of autoantibody-PF4 complexes, the latter being achieved by administration of high-dose intravenous immunoglobin (IVIG). Steroids, which can theoretically inhibit the production of new antibodies, have been used in combination with IVIG. In severe cases, plasma exchange should be used for clearing autoantibodies. Monoclonal antibodies, such as rituximab and eculizumab, can be considered when other therapies fail. Routine platelet transfusions, aspirin, and warfarin should be avoided because of the possibility of worsening thrombosis and magnifying bleeding risk.

Conclusions and Relevance

Adverse events like VITT, while uncommon, have been described despite vaccination remaining the most essential component in the fight against the COVID-19 pandemic. While it seems logical to consider the use of types of vaccines (eg, mRNA-based administration) in individuals at high risk, treatment should consist of therapeutic anticoagulation mostly with nonheparin products and IVIG.

Anti-neutrophil cytoplasmic antibody-associated vasculitis accompanied by type II heparin-induced thrombocytopenia resulting in asymptomatic cerebral infarction: a case report

Background

Heparin-induced thrombocytopenia (HIT) involves platelet activation and aggregation caused by heparin or HIT antibodies associated with poor survival outcomes. We report a case of HIT that occurred after hemodialysis was started for rapidly progressive glomerulonephritis (RPGN), which was caused by anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV), and ultimately resulted in asymptomatic cerebral infarction.

Case presentation

A 76-year-old Japanese man was urgently admitted to our hospital for weight loss and acute kidney injury (serum creatinine: 12 mg/dL). Hemodialysis therapy was started using heparin for anticoagulation. Blood testing revealed elevated titers of myeloperoxidase anti-neutrophil cytoplasmic antibodies, and renal biopsy revealed crescentic glomerulonephritis with broad hyalinization of most of the glomeruli and a pauci-immune staining pattern. These findings fulfilled the diagnostic criteria for microscopic polyangiitis, and the patient was diagnosed with RPGN caused by AAV. Steroid pulse therapy, intermittent pulse intravenous cyclophosphamide, and oral steroid therapy failed to improve the patient’s renal function, and maintenance dialysis was started. However, on day 15, his platelet count had decreased to 47,000/µL, with clotting observed in the hemodialysis catheter. Magnetic resonance imaging of the head identified acute asymptomatic brain infarction in the left occipital lobe, and a positive HIT antibody test result supported a diagnosis of type II HIT. During hemodialysis, the anticoagulant treatment was changed from heparin to argatroban. Platelet counts subsequently normalized, and the patient was discharged. A negative HIT antibody test result was observed on day 622.

Conclusions

There have been several similar reports of AAV and HIT co-existence. However, this is a rare case report on cerebral infarction with AAV and HIT co-existence. Autoimmune diseases are considered risk factors for HIT, and AAV may overlap with other systemic autoimmune diseases. To confirm the relationship between these two diseases, it is necessary to accumulate more information from future cases with AAV and HIT co-existence. If acute thrombocytopenia and clotting events are observed when heparin is used as an anticoagulant, type II HIT should always be considered in any patient due to its potentially fatal thrombotic complications.

Global cerebral infarction after aortic arch replacement surgery in a patient with postoperatively revealed factor XII deficiency: a case report

Background

This case report presents a case of a patient with global cerebral infarction of uncertain etiology following an emergency surgery for acute type A aortic dissection. As a result, factor XII deficiency was revealed postoperatively. To date, there have been several reports of cardiovascular surgery in patients with factor XII deficiency. However, all previous reports were of patients whose factor XII deficiency had been detected preoperatively; therefore, before this, there had been no reports of complications associated with factor XII deficiency following cardiovascular surgery.

Case presentation

We report a case of emergency aortic arch replacement surgery for acute type A aortic dissection in a 57-year-old Japanese man. A blood test prior to the surgery showed coagulopathy, a platelet count of 117 × 10⁹/L, a prothrombin time–international normalized ratio of 1.78, an activated partial thromboplastin time of 69.7 seconds, and fibrinogen < 50 mg/dl. A smaller-than-usual dose of heparin (8000 IU) was administered because the patient’s activated clotting time was extremely prolonged (> 999 seconds). After the heparin administration, the activated clotting time, measured every 30–60 minutes, remained unchanged (> 999 seconds); therefore, additional heparin was not administered during the surgery, and there was no clinical problem during cardiopulmonary bypass. However, a diagnosis of global cerebral infarction was made on the first postoperative day. An additional blood coagulation test performed on postoperative day 9 revealed factor XII deficiency (8.0%). Regarding the reason that global cerebral infarction occurred in the present case, two reasons were considered: One was factor XII deficiency itself, and the other was low-dose heparin administration during the cardiopulmonary bypass due to excessively prolonged activated clotting time caused by factor XII deficiency.

Conclusions

Factor XII deficiency should be considered in patients with prolonged activated clotting time and spontaneous thrombosis in vascular surgeries. Moreover, the present case emphasizes that management of heparin during cardiopulmonary bypass should not be performed on the basis of activated clotting time monitoring alone, especially in a case with prolonged activated clotting time.

Layer-by-Layer Deposition of Hyaluronan and Quercetin-Loaded Chitosan Nanoparticles onto Titanium for Improving Blood Compatibility

Surface modification is an effective way to improve the hemocompatibility of biomaterials. Quercetin has significant anticoagulation and antithrombotic effects, and thus it is a promising candidate agent for the surface modification of blood-contacting materials. In this study, quercetin was successfully encapsulated in tripolyphosphate–chitosan nanoparticles (TCs) based on the ionic gelation of chitosan with tripolyphosphate (TPP) anions. Then, hyaluronan acid (HA)/quercetin-loaded TPP–chitosan nanoparticle (QTCs) films, in addition to HA/TCs films, were prepared separately using an electrostatic layer-by-layer self-assembly technique. The encapsulation of quercetin in the chitosan nanoparticles was confirmed by UV spectra. The quercetin-loaded multilayer coatings were also successfully self-assembled, as confirmed by the UV spectra and contact angle measurements. Platelet adhesion experiments were carried out with platelet-enriched plasma so as to evaluate the blood compatibility of the different samples. There were many platelets on the surfaces of the glass and HA/TC-coated titanium, which were partially activated but not aggregated. Meanwhile, many more platelets were observed on the uncoated titanium surfaces, most of which developed pseudopodia. By contrast, the platelet adhesion and activation were reduced remarkably on the surface of the HA/QTC-coated titanium. These results showed that the multilayer coatings containing quercetin could act as potential biomaterials to improve the anticoagulation performance of blood-contacting materials.

Acute non-heparin-induced thrombocytopenia during hemodiafiltration in a patient with multiple myeloma

This report demonstrates that not only heparin-induced thrombocytopenia, but also hemodialysis conditions (platelet activation due to hemodiafiltration and heparin underdosing) may markedly reduce the platelet count and cause clotting in the hemodialysis circuit in patients in a hypercoagulable state. The clot prevention effects of bortezomib are therefore of great importance.

Heparin-induced thrombocytopenia (HIT): Identification and treatment pathways

Heparin-induced thrombocytopenia (HIT) is a major health problem, especially in cardiac surgery theaters, cardiac catheterization labs, and intensive care units. Some patients with HIT develop serious thrombotic complications like limb ischemia and gangrene, while others may not develop such complications and have only mild thrombocytopenia. Current laboratory diagnostic tools incur significant time delays before confirming HIT, therefore upon clinical suspicion, treatment of HIT should start immediately while awaiting laboratory results. This is a review of the types, phases, pathophysiology, clinical presentation and diagnosis of HIT, and its current management strategies.

New-onset acute thrombocytopenia in hospitalized patients: pathophysiology and diagnostic approach

Thrombocytopenia is a hematological finding commonly encountered in daily clinical practice from asymptomatic clinic patients to critically ill intensive care unit patients. A broad spectrum of etiologies and variation in clinical presentation often present a diagnostic challenge. Furthermore, concomitant presence of thrombosis and thrombocytopenia, as in cases of thrombotic thrombocytopenia, complicates the management. In hospitalized patients, new-onset thrombocytopenia is an important reason for hematology consultation. Therefore, it is of utmost importance that the etiology is diagnosed accurately. In addition, a basic understanding of the pathophysiology and the differential diagnosis avoids delay in the diagnosis and leads to rapid initiation of treatment. This review will address causes of thrombocytopenia that arises in hospitalized patients with an emphasis on the pathophysiological basis of each disorder.

Acute pulmonary edema and thrombocytopenia following venous air embolism during sitting position neurosurgery

Venous air embolism (VAE) is a well-known complication of sitting position neurosurgery which most characteristically manifests as mild to severe hemodynamic alterations. Development of pulmonary edema is a known, though infrequent, manifestation of VAE. We report here the occurrence of acute pulmonary edema without accompanying hemodynamic changes in a patient undergoing retromastoid craniotomy and tumor decompression in the sitting position. The patient required supportive treatment and elective ventilation for 11 days before the edema resolved. He also developed significant postoperative thrombocytopenia which though, was self-limiting. Thus, VAE may manifest with atypical manifestations like pulmonary edema and thrombocytopenia that can significantly contribute to postoperative patient morbidity.

Cardiopulmonary Bypass Without Heparin

Due to familiarity, short half-life, ease of monitoring, and the availability of a reversal agent, heparin remains the anticoagulant of choice for cardiac operations requiring cardiopulmonary bypass (CPB). However, occasionally patients require CPB but should not receive heparin, most often because of acute or subacute heparin-induced thrombocytopenia (HIT). In these cases, if it is not feasible to wait for the disappearance of HIT antibodies, an alternative anticoagulant must be selected. A number of non-heparin anticoagulant options have been explored. However, current recommendations suggest the use of a direct thrombin inhibitor such as bivalirudin. This review describes the use of heparin alternatives for the conduct of CPB with a focus on the direct thrombin inhibitors.

Management of Patients with Heparin-Induced Thrombocytopenia During Cardiac Surgery

The role of heparin-induced thrombocytopenia and its possibly severe complications in patients undergoing cardiac surgery is increasingly appreciated. Increasing evidence indicates that in patients without the presence of antibodies, unfractionated heparins can be safely used during cardiopulmonary bypass, if their employment is restricted to this short period. This strategy is the first choice in patients with a current negative status of antibodies and in patients in whom surgery can be delayed until antibodies cannot be detected by laboratory tests. To date, however, no alternative anticoagulant to heparin during cardiopulmonary bypass has been approved. With the introduction of the class of direct thrombin inhibitors, effective anticoagulants have become available; however, they have no antidote and require specific monitoring. The availability of direct thrombin inhibitors is currently restricted. The administration of unfractionated heparin with anti-platelet agents such as prostaglandins or the short-acting platelet glycoprotein llb/Illa antagonist tirofiban is another option. Despite successful use of these strategies in fairly large numbers of patients, recent information suggests that in the case of tirofiban, renal failure may cause persistence of the agent with subsequent severe hemorrhage. If surgery is restricted to coronary artery bypass grafting, recent data show that off-pump strategies with use of the direct thrombin inhibitor bivalirudin appear to be a promising option. Therefore, if surgery cannot be postponed, the anticoagulation protocol and the surgical strategy must be adjusted to the condition of the patient and the experience of the center in order to reduce the risk of these “offlabel” strategies.

Rheolytic thrombectomy in patient with acute pulmonary embolism, heparin-induced thrombocytopenia and recent stoke. When percutaneous treatment is the only therapeutic alternative

To report the combined use of rheolytic thrombectomy (RT) and inferior vena cava (IVC) filter placement in the setting of acute pulmonary embolism (PE), heparin-induced thrombocytopenia (HIT) type II (HIT-II) and recent ischemic stroke. A 66-year-old man with an HIT-II and recent ischemic stroke was referred to our institution from a secondary regional center for acute PE and left deep vein thrombosis (DVT), confirmed at chest computed tomography (CT) and lower limb ultrasound, respectively. RT was attempted because intravenous heparin anticoagulation was contraindicated by the patient’s medical history while recent ischemic stroke contraindicated thrombolysis. An Angiojet® catheter was used to perform RT. An IVC filter was placed after the procedure. The patient was discharged after 13 days and did very well, both at the 6- and 12-month follow-ups, with no recurrence of the venous thromboembolism. This case demonstrates the usefulness of RT in treating acute PE in clinically difficult scenarios, especially when thrombolytic therapy is contraindicated.

Thrombotic Complications in Three Hemodialysis Patients With Heparin-Induced Thrombocytopenia Type I

Although unfractionated heparin is the most commonly used anticoagulant for hemodialysis and has been associated with bleeding episodes, a more devastating complication that can occur is heparin-induced thrombocytopenia (HIT). It is believed that HIT type II is much more dangerous than type I, because HIT type II is associated with thromboembolic complications whereas there are no such complications in HIT type I. However, increased clot formation in the extracorporeal circuit during hemodialysis with unfractionated heparin is sometimes experienced by not only patients with HIT type II but also those with HIT type I. Three patients with HIT type I are presented who suffered from clot formation during hemodialysis, and in whom 81 mg of aspirin and/or cessation of heparin was prescribed. All three patients had received recombinant human erythropoietin (rHuEpo). Both heparin and rHuEpo induce enhanced platelet aggregation; therefore, it is possible that even HIT type I patients may suffer clot formation in the extracorporeal circuit due to platelet activation via the synergistic effects of unfractionated heparin and rHuEpo.

A heparin-mimicking reverse thermal gel for controlled delivery of positively charged proteins

Positively charged therapeutic proteins have been used extensively for biomedical applications. However, the safety and efficacy of proteins are mostly limited by their physical and chemical instability and short half-lives in physiological conditions. To this end, we created a heparin-mimicking sulfonated reverse thermal gel as a novel protein delivery system by sulfonation of a graft copolymer, poly(serinol hexamethylene urea)-co-poly(N-isopropylacylamide), or PSHU-NIPAAm. The net charge of the sulfonated PSHU-NIPAAm was negative due to the presence of sulfonate groups. The sulfonated PSHU-NIPAAm showed a typical temperature-dependent sol-gel phase transition, where polymer solutions turned to a physical gel at around 32°C and maintained gel status at body temperature. Both in vitro cytotoxicity tests using C2C12 myoblast cells and in vivo cytotoxicity tests by subcutaneous injections demonstrated excellent biocompatibility. In vitro release tests using bovine serum albumin revealed that the release from the sulfonated PSHU-NIPAAm was more sustained than that from the plain PSHU-NIPAAm. Furthermore, this sulfonated PSHU-NIPAAm system did not affect protein structure after 70-day observation periods.

Emphasis on the Role of PF4 in the Incidence, Pathophysiology and Treatment of Heparin Induced Thrombocytopenia

Heparin Induced Thrombocytopenia (HIT) is caused by antibodies that recognize platelet factor 4 (PF4) associated with polyanionic glycosaminoglycan drugs or displayed on vascular cell membranes. These antibodies are elicited by multimolecular complexes that can occur when heparin is administered in clinical settings associated with abundant PF4. Heparin binding alters native PF4 and elicits immune recognition and response. While the presence of heparin is integral to immunogenesis, the HIT antibody binding site is within PF4. Thus HIT antibodies develop and function to cause thrombocytopenia and/or thrombosis only in the presence of PF4. Future emphasis on understanding the biology, turnover and regulation of PF4 may lead to insights into the prevention and treatment of HIT.

Heparin-induced thrombocytopenia: is it a graft-threatening complication?

Heparin-induced thrombocytopenia (HIT), a prothrombotic complication of heparin therapy, can lead to serious thromboembolic events and cause significant morbidity and mortality. We aim to study the prevalence of HIT in the transplant population at our institute. This is a retrospective, single-center study which looked into the transplant database over a 25-year period. In patients with clinical suspicion of HIT, the 4T score was used, and laboratory tests such as ELISA HIT antibody and functional serotonin release assay, along with clinical manifestation of thromboembolic events were reviewed. Medical records of 2800 patients who underwent transplantation from January 1985 to December 2010 were reviewed. HIT antibody assay was performed in 262 patients from this group in which HIT was suspected. Of these, only 48 patients were HIT antibody positive along with moderate to high 4T score. The mean 4T score was 6.75 ± 1.4. Thrombotic complications were seen in 11 patients, with the highest in cardiac transplant recipients. Direct thrombin inhibitor (DTI) therapy was used in only eight patients who had thrombotic event. No other complications or mortality was reported in any of the HIT antibody-positive transplant patients. To our knowledge, this is the first study of its kind that has shown very low incidence of HIT in the transplant population except for in cardiac transplant recipients.

Acute Stent Thrombosis and Heparin Induced Thrombocytopenia in a Patient With ST-Segment Elevation Myocardial Infarction

Heparin is an essential drug in the treatment of acute coronary syndrome and it is used during percutaneous coronary intervention (PCI). Heparin-induced thrombocytopenia (HIT), albeit a serious complication of heparin therapy characterized by thrombocytopenia and high risk for venous and arterial thrombosis, has rarely been previously reported during PCI. We report a case of an acute stent thrombosis due to an unusual cause, HIT during primary PCI, in a patient with acute myocardial infarction.

A cohort study investigating compliance with guidelines for platelet count monitoring during heparin thromboprophylaxis

BACKGROUND

Heparin is the most common agent used for prevention of venous thromboembolism. To promote early detection of heparin-induced thrombocytopenia, guidelines recommend episodic platelet count monitoring for specified patient populations. However, physician compliance with these guidelines has never been reported for patients receiving heparin for pharmacologic prophylaxis.

AIM

The aim of this study was to evaluate the frequency of and factors associated with physician failure to monitor patient platelet counts.

RESULTS

We conducted a retrospective cohort study of 2350 admissions of patients aged ≥ 18 years who received ≥ 4 consecutive days of prophylactic heparin. There was nonadherence to monitoring recommendations in 659 (28%) patients. Monitoring was not more likely among patients for whom monitoring was recommended compared with patients for whom no monitoring was recommended (31% vs 27%; adjusted hazard ratio, 0.9; 95% CI, 0.7-1.1). Compared with patients admitted to the general medicine service, monitoring was significantly less common among patients admitted to orthopedic surgery or obstetric-gynecologic services (adjusted hazard ratio, 1.6; 95% CI, 1.1-2.2 and adjusted hazard ratio, 2.4; 95% CI, 1.8-3.2, respectively). A decrease in platelet count (≥ 50%) was detected in 90 (4%) patients, but in only 12 (11%) patients was heparin stopped, and in only 11 (12%) patients were heparin-induced thrombocytopenia antibody levels obtained. Of the 11 patients for whom heparin-induced thrombocytopenia antibody levels were obtained, 6 (0.26% of the patient population) were positive.

CONCLUSION

We found that compliance by physicians with platelet count monitoring recommendations was poor for patients who had received heparin for venous thromboembolism prophylaxis, and platelet count monitoring appeared to be unrelated to American College of Chest Physicians recommendations for routine monitoring. Compliance was particularly poor in orthopedic surgery and obstetric-gynecologic services.

Risks and complications of coronary angiography: a comprehensive review

Coronary angiography and heart catheterization are invaluable tests for the detection and quantification of coronary artery disease, identification of valvular and other structural abnormalities, and measurement of hemodynamic parameters. The risks and complications associated with these procedures relate to the patient’s concomitant conditions and to the skill and judgment of the operator. In this review, we examine in detail the major complications associated with invasive cardiac procedures and provide the reader with a comprehensive bibliography for advanced reading.

Managing adverse effects and drug-drug interactions of antiplatelet agents

Antiplatelet therapies have reduced the frequency of adverse events associated with plaque rupture in several clinical situations. These therapies include established antiplatelet agents (such as aspirin, clopidogrel, or glycoprotein IIb/IIIa inhibitors) as well as new agents (such as prasugrel and ticagrelor). In this Review, we address the most important adverse events of antiplatelet therapy, including hemorrhage, hematologic reactions, and dyspnea. We discuss strategies to reduce the incidence of complications and outline potential methods to manage adverse reactions. Interactions between antiplatelet agents and other drugs--such as proton-pump inhibitors, calcium-channel blockers, statins, warfarin, or NSAIDs--are also addressed, as well as specific issues relating to the use of antiplatelet therapies in elderly patients.

Postoperative Care of the Cardiac Surgical Patient

The subspecialty of interventional cardiology began in 1977. Since then, the discipline of interventional cardiology has matured rapidly, particularly with regards to ischemic heart disease. As a result, more patients are undergoing percutaneous catheter interventional therapy for ischemic heart disease and fewer patients are undergoing surgical myocardial revascularization. Those patients referred for surgical revascularization are generally older and have more complex problems. Furthermore, as the population ages more patients are referred to surgery for valvular heart disease. The result of these changes is a population of surgical patients older and sicker than previously treated.

Six-month follow-up of patients with in-hospital thrombocytopenia during heparin-based anticoagulation (from the Complications After Thrombocytopenia Caused by Heparin [CATCH] registry)

Thrombocytopenia is a predictor of adverse outcomes in patients with acute coronary syndromes and in critically ill patients. The Complications After Thrombocytopenia Caused by Heparin (CATCH) registry was designed to explore the incidence, management, and clinical consequences of in-hospital thrombocytopenia occurring during heparin-based anticoagulation in diverse clinical settings. We conducted a prospective observational study of 37 United States hospitals participating in the CATCH registry to assess the relation of in-hospital thrombocytopenia to long-term outcomes. A total of 2,104 patients at increased risk of developing in-hospital thrombocytopenia or thrombosis were identified, and the 6-month mortality and rehospitalization rates were determined. Thrombocytopenia was not a significant predictor of 6-month mortality. In an adjusted model for in-hospital death in this cohort, thrombocytopenia had an odds ratio of 3.59 (95% confidence interval 2.24 to 5.77). The postdischarge mortality rate at 6 months was 9.7%. No significant difference was observed in the long-term mortality between patients who developed thrombocytopenia and those who did not. Thrombocytopenia was a weak, but statistically significant, predictor of a composite of mortality and rehospitalization at 6 months (hazards ratio 0.80, 95% confidence interval 0.65 to 0.98, p = 0.03). In conclusion, the 6-month mortality rate among heparin-treated patients with thrombocytopenia is high, although the risk independently related to thrombocytopenia appears to be restricted to the acute hospital phase.

What is the optimal anticoagulation level with argatroban during percutaneous coronary intervention?

Argatroban is increasingly used in patients with heparin-induced thrombocytopenia. Although the recommended activated clotting time during percutaneous coronary intervention is 300-450 s, this recommendation is based on the limited data. This single-center, retrospective study evaluated the efficacy (composite of death, myocardial infarction, or urgent revascularization) and safety (evaluated by thrombolysis in myocardial infarction major bleeding) of argatroban during percutaneous coronary intervention according to activated clotting time levels. Patients were divided into three groups according to the activated clotting time achieved during the procedure (<300s, 300-450s, and >450 s). In this study, 120 consecutive patients with confirmed or suspected heparin-induced thrombocytopenia received argatroban (241 +/- 104 mug/kg bolus, followed by a 18 +/- 10 microg/kg per min infusion) during percutaneous coronary intervention. The indication for percutaneous coronary intervention was stable angina in 20% of patients, unstable angina or non-ST elevation myocardial infarction in 58%, and ST elevation myocardial infarction in 22%. An adjunctive glycoprotein IIb/IIIa inhibitor was used in 56 patients (46.7%). When divided into three groups on the basis of the activated clotting time (<300, 300-450, >450 s), no significant difference was observed between the groups in the efficacy endpoint, which occurred in 9.8% (6/61) of patients in the group with activated clotting time less than 300 s, 19.6% (9/46) of patients in the group with activated clotting time 300-450 s, and 7.7% (1/13) of patients in the group with activated clotting time more than 450 s (P = 0.58). The rate of major bleeding was higher in the group of patients with activated clotting time more than 450 s (1.6, 0, and 15.4% patients, respectively; P = 0.006). These results suggest that in patients undergoing percutaneous coronary intervention, argatroban provides adequate anticoagulation with a low bleeding rate, when activated clotting time is maintained below 450 s.

Heparin-dependent antibodies and thrombosis without heparin-induced thrombocytopenia

Although heparin-dependent antibodies (HDAs) typically manifest with thrombocytopenia as in heparin-induced thrombocytopenia (HIT), they may also manifest with preserved platelet counts. We describe a 35-year-old woman who developed severe thrombotic complications due to heparinization and unrecognized HDAs. She had received subcutaneous heparin as prophylaxis for deep vein thrombosis during a 5-day hospitalization for postpartum cardiomyopathy. Five days after discharge (day 1), she developed bilateral lower extremity arterial thrombi and underwent heparinization and successful lower extremity thrombectomies. A pulmonary embolus and hepatic and renal infarcts were then found. On days 2-6, the patient experienced a myocardial infarction, ischemic cerebrovascular accident, recurrent lower extremity arterial thrombus, and splenic infarct. On day 7, blood obtained on day 4 was found to be strongly positive for HDAs. In the interim, the patient had been transitioned to warfarin. Her platelet counts were never less than 75% of baseline and were consistently above 200 x 10(3)/mm(3). Hypercoagulability studies were negative. The patient's score on the Naranjo adverse drug reaction probability scale indicated that the relationship between this adverse reaction and heparin was probable. An extensive MEDLINE search located 22 other reports of patients who developed HDAs, sometimes associated with thrombosis, but whose platelet counts did not decrease. As with our patient, many of these case reports described clinicians who overlooked thrombosis due to HDAs because the patients did not have HIT. Clinicians should be cognizant of this possibility and consider a diagnosis of HDAs in patients with ongoing thrombosis who are receiving heparin therapy. It is strongly recommended that heparin be substituted with another anticoagulant in such cases until the presence of HDAs can be definitively ruled out.

Thrombocytopenia in patients with an acute coronary syndrome (from the Global Registry of Acute Coronary Events [GRACE])

The incidence of thrombocytopenia after hospital admission, patient and treatment characteristics, and outcomes in patients enrolled in the prospective multinational GRACE were examined. Heparin (unfractionated or low molecular weight) and glycoprotein IIb/IIIa-inhibition can be associated with immune-mediated thrombocytopenia of clinical importance. The prevalence of thrombocytopenia in patients with acute coronary syndromes (ACSs) in general and specifically related to these therapies and associated outcomes have been studied little outside of clinical trials. Patients with an ACS were stratified into 4 groups of those with heparin-induced thrombocytopenia (HIT), those with glycoprotein IIb/IIIa-associated thrombocytopenia (GAT), those with other thrombocytopenia (not diagnosed as HIT or associated with glycoprotein inhibitors), and those with no thrombocytopenia. From June 2000 to September 2007, a total of 52,647 patients with an ACS and information for platelet count were enrolled in GRACE. Of these, 152 (0.3%) were reported to develop HIT, 324 (0.6%) developed GAT, and 368 (0.7%) developed other thrombocytopenia. Patients with HIT, GAT, or other thrombocytopenia were significantly more likely to die in the hospital versus those without these diseases (adjusted odds ratio [OR] 1.94, 95% confidence interval [CI] 1.07 to 3.53; adjusted OR 3.45, 95% CI 2.35 to 5.05; and adjusted OR 2.83, 95% CI 1.97 to 4.06, respectively). They were also more likely to experience major bleeding, (re)infarction, or stroke. In conclusion, in this large multinational registry, 1.6% of patients with ACS were reported to develop thrombocytopenia, with only 0.3% being HIT. Regardless of whether patients had clinically recognized HIT, GAT, or other thrombocytopenia, all 3 groups had significantly higher rates of major bleeding, recurrent infarction, stroke, and death.

Weight-based argatroban dosing nomogram for treatment of heparin-induced thrombocytopenia

BACKGROUND

Manufacturer recommendations for argatroban use in the setting of heparin-induced thrombocytopenia (HIT) state that the dosage should be titrated to a goal activated partial thromboplastin time (aPTT) of 1.5-3 times the baseline aPTT. The lack of a clear dosing strategy with argatroban may result in delayed stabilization of aPTT. There are no published nomograms to guide the dosing of argatroban.

OBJECTIVE

To study the anticoagulant effect and incidence of bleeding and thrombotic events in patients receiving argatroban, with doses determined using a weight-based nomogram.

METHODS

Patients with suspected or documented HIT at an 800-bed teaching community hospital were prospectively treated, in a nonrandomized, nonblinded manner, with argatroban; dosage adjustments were made according to 1 of 2 variations of a dosing nomogram: standard or hepatic/critically ill. The primary outcomes were time to aPTT stabilization and percentage of patients whose aPTTs were within the therapeutic range of 45-90 seconds at 6, 12, 24, 48, 72, and 96 hours. Secondary outcomes were the percentage of patients whose aPTTs were subtherapeutic, supratherapeutic, or above the therapeutic threshold of 45 seconds at each time interval; incidence of thrombotic events; number of dosage adjustments to achieve stabilization; and number of major bleeding events.

RESULTS

Fifty-one patients were prospectively treated using the standard (n = 34) and hepatic/critically ill (n = 17) nomograms. Mean time to aPTT stabilization was 16.25 hours with the standard nomogram and 27.05 hours with the hepatic/critically ill nomogram. The percentages of patients with aPTTs within the therapeutic range at each time interval were 82.4%, 82.4%, 88.2%, 96.4%, 100%, and 100% with the standard nomogram and 58.8%, 82.4%, 76.5%, 93.3%, 100%, and 90.9% with the hepatic/critically ill nomogram. There were no thrombotic events after the initiation of argatroban. Three cases of major bleeding occurred.

CONCLUSIONS

The nomogram is an effective dosing tool for achieving and maintaining therapeutic levels of anticoagulation.

The incidence of heparin-induced thrombocytopenia Type II in patients with subarachnoid hemorrhage treated with heparin versus enoxaparin

Object

Heparin-induced thrombocytopenia Type II (HIT II) is a serious complication that occurs in 0.2–3% of patients treated with heparin and is associated with a high risk of thrombotic events. One center recently reported an incidence of HIT II of 15% in a population of patients with aneurysmal subarachnoid hemorrhage (aSAH). Because these patients are typically exposed to heparin during angiography, controversy exists regarding whether prophylaxis with enoxaparin rather than heparin affords any reduction in the risk of developing HIT II. In this study, the authors investigated the effect of heparin compared with enoxaparin on the incidence of HIT II in patients with aSAH.

Methods

The authors reviewed the medical records of 300 patients treated for aSAH who received thromboprophylaxis with either heparin or enoxaparin, and identified patients who developed HIT II. The incidences of HIT II in the 2 treatment groups were then compared.

Results

One hundred sixty-six patients with aSAH were treated with heparin, and 134 patients were treated with enoxaparin. Sixteen (5.3%) of 300 patients met the diagnostic criteria for HIT II. Of those treated with heparin, 8 (4.8%) of 166 developed HIT II, compared with 8 (6%) of 134 treated with enoxaparin (difference not significant).

Conclusions

The authors report a lower incidence of HIT II in patients with aSAH than has previously been reported. The data also suggest that patients with aSAH who receive heparin are at no greater risk of developing HIT II than those who receive enoxaparin. This finding challenges the merit of choosing enoxaparin rather than heparin for thromboprophylaxis in patients with a SAH.

Effects of critical illness and organ failure on therapeutic argatroban dosage requirements in patients with suspected or confirmed heparin-induced thrombocytopenia

BACKGROUND

Critically ill patients often require therapeutic argatroban dosages lower than those recommended in package labeling. The magnitude of dosage alteration in relation to severity of organ failure is unknown.

OBJECTIVE

To compare therapeutic argatroban dosages between critically ill and noncritically ill patients with confirmed or suspected heparin-induced thrombocytopenia and investigate the relationship between total Sequential Organ Failure Assessment (SOFA) score and therapeutic argatroban dosage.

METHODS

This retrospective cohort study was conducted at an urban academic medical center. Adults without Child-Pugh class C hepatic dysfunction who received argatroban for more than 24 hours over a 3-year period were included. Therapeutic argatroban dosage was that resulting in 2 consecutive activated partial thromboplastin time (aPTT) values 1.5-3 times the patient-specific baseline obtained at least 4 hours apart. Initial argatroban dosages were at the discretion of the managing service.

RESULTS

Fifty-three patients (critically ill, n = 34; noncritically ill, n = 19) were included. Critically ill patients had higher median [interquartile range] Acute Physiology and Chronic Health Evaluation (APACHE II) (17 [12-21] vs 10 [3.25-17.75]; p = 0.007) and SOFA (11 [7-13] vs 2 [0-2.75]; p < 0.001) scores. Critically ill patients required lower mean +/- SD therapeutic argatroban dosage (0.6 +/- 0.5 vs 1.4 +/- 0.9 microg/kg/min; p < 0.001). There was no significant difference in time to therapeutic aPTT or proportion of aPTTs within therapeutic range. Argatroban dosage was inversely related to SOFA score tertiles (<6: 1.34 +/- 0.82 microg/kg/min; 6-9: 0.93 +/- 0.54; > or =10: 0.40 +/- 0.27; p < 0.001). Total SOFA score at the time of argatroban initiation was independently associated with an argatroban dosage less than 0.75 microg/kg/min (OR 1.5, 95% CI 1.2 to 1.8; p < 0.001). Adverse events were similar between groups.

CONCLUSIONS

Critically ill patients with single or multiple organ failure require lower therapeutic argatroban dosages compared with noncritically ill patients. Because of an inverse relationship with SOFA score, initial argatroban dosage in critically ill patients should be based on the presence and magnitude of organ failure.