AHA Scientific Statement: Guide to anticoagulant therapy: heparin: a statement for healthcare professionals from the American Heart Association

Use of suture-mediated closure device system after inadvertent medport placement in the subclavian artery leading to multi-focal ischaemic infarct: a case report

Background

Totally implantable venous access devices or chemoports are progressively being used in oncologic patients for long-term chemotherapy administration. We present the case of an iatrogenic arterial catheter placement in the aortic arch complicated with multi-focal ischaemic stroke.

Case summary

A case of a 73-year-old woman with a history of hypertension, diabetes mellitus, pineal gland tumour status post ventriculoperitoneal shunt, and breast and bladder cancer presented with a 2-week history of impaired balance, dysarthria, and right-sided facial drop. The chemoport was placed less than a month prior to the onset of symptoms at another institution. A brain magnetic resonance imaging revealed a left hemispheric supra- and infra-tentorial subacute ischaemic infarcts. The head and neck computed tomography angiography notably showed a misplaced venous port at the left subclavian artery with a distal tip projecting towards the ascending aortic arch, revealing the most likely aetiology of multi-focal ischaemic stroke. The patient underwent successful subclavian artery catheter extraction and endovascular repair with a suture-mediated closure device system without complications.

Discussion

Subclavian artery iatrogenic cannulation may lead to catastrophic outcomes, including stroke. A high level of suspicion for venous port misplacement must be entertained when ipsilateral multi-focal ischaemic infarct occurs in time relation to catheter placement. Conducting an endovascular catheter retrieval and using a suture-mediated closure device is an alternative approach to manual compression in locations where achieving an haemostasis is challenging. A suture-mediated closure device system might be useful for anatomy not amenable to manual compression, such as the subclavian artery.

Assessing the impact of different heparin dosing regimens for cardiopulmonary bypass on anticoagulation: the HepDOSE pilot study

PURPOSE

It has been suggested that a larger heparin dose during cardiopulmonary bypass (CPB) is associated with reduced perioperative coagulopathy and thromboembolic complications. We investigated the effect of different heparin doses during routine elective cardiac surgery. Our primary outcomes include blood loss and transfusion and secondary outcomes investigate the effects on coagulation biomarkers.

METHODS

In this prospective pilot trial, we allocated 60 patients undergoing cardiac surgery on CPB in a single tertiary cardiac centre into three groups to receive an initial dose of 300, 400, or 500 units (U) per kilogram of intravenous heparin prior to the commencement of CPB. Blood was sampled after induction of anesthesia, at 30 and 60 min of CPB, and three minutes after heparin reversal with protamine. Samples were analyzed for fibrinopeptide A (FPA), fibrinopeptide B (FPB), D-dimer, and thrombin-antithrombin (TAT) complexes. Postoperative blood loss and transfusion was measured for the first 24-hr period after surgery.

RESULTS

The total mean (95% CI) administered heparin dose in the 300 U·kg-1, 400 U·kg-1, and 500 U·kg-1 groups were 39,975 (36,528 to 43,421) U, 43,195 (36,940 to 49,449) U and 47,900 (44,807 to 50,992) U, respectively. There were no statistically significant differences in FPA, FPB or D-dimer levels at the measured time intervals. There was a trend towards lower TAT levels while on CPB with greater heparin dosing, which was statistically significant after the administration of protamine. The clinical significance appears to be negligible, as there is no difference in overall blood loss and amount of packed red blood cell transfusion or other blood product transfusion.

CONCLUSION

This pilot study indicates that, while larger heparin dosing for routine cardiac surgery results in subtle biochemical changes in coagulation, there is no demonstrable benefit in postoperative blood loss or transfusion requirements.

Feasibility and safety values of activated clotting time-guided systemic heparinization in coil embolization for unruptured intracranial aneurysms

OBJECTIVE

This study aimed to evaluate the feasibility and safety values of activated clotting time (ACT)-guided systemic heparinization in reducing periprocedural thrombosis and bleeding complications during coil embolization of unruptured intracranial aneurysms.

METHODS

A total of 228 procedures performed on 213 patients between 2016 and 2021 were included in the retrospective analysis. The target ACT was set at 250 s. Logistic regression was performed to assess predictors for the occurrence of thrombosis and bleeding. Receiver operating characteristic (ROC) analyses were employed to determine the optimal cut-off values for ACT, heparinization, and procedure time.

RESULTS

Most (85.1%) of procedures were stent-assisted embolization. The mean baseline ACT was 128.8 ± 45.7 s. The mean ACT at 20 min after the initial intravenous heparin loading of 78.2 ± 18.8 IU/kg was 185 ± 46.4 s. The mean peak ACT was 255.6 ± 63.8 s with 51.3% (117 cases) achieving the target ACT level. Peak ACT was associated with symptomatic thrombosis (OR per second, 1.008; 95% CI, 1.000-1.016; P = 0.035) (cut-off value, 275 s; area under ROC (AUROC), 0.7624). Total administered heparin dose per body weight was negatively associated with symptomatic thrombosis (OR per IU/kg, 0.972; 95% CI, 0.949-0995; P = 0.018) (cut-off value, 294 IU/kg; AUROC, 0.7426) but positively associated with significant bleeding (OR, 1.008 per IU/kg; 95% CI, 1.005-1.012; P <0 .001) (cut-off value, 242 IU/kg; AUROC, 0.7391). Procedure time was significantly associated with symptomatic thrombosis (OR per minute, 1.05; 95% CI, 1.017-1.084; P value = 0.002) (cut-off value, 158 min; area under ROC, 0.8338).

CONCLUSION

This study demonstrated that ACT-guided systemic heparinization was feasible to achieve the target ACT value and proposes probable safety thresholds to prevent periprocedural complications through reducing procedure time during coil embolization of unruptured intracranial aneurysms in the stent era.

Docking and Molecular Dynamics Simulations Clarify Binding Sites for Interactions of Novel Marine Sulfated Glycans with SARS-CoV-2 Spike Glycoprotein

The entry of SARS-CoV-2 into the host cell is mediated by its S-glycoprotein (SGP). Sulfated glycans bind to the SGP receptor-binding domain (RBD), which forms a ternary complex with its receptor angiotensin converting enzyme 2. Here, we have conducted a thorough and systematic computational study of the binding of four oligosaccharide building blocks from novel marine sulfated glycans (isolated from Pentacta pygmaea and Isostichopus badionotus) to the non-glycosylated and glycosylated RBD. Blind docking studies using three docking programs identified five potential cryptic binding sites. Extensive site-targeted docking and molecular dynamics simulations using two force fields confirmed only two binding sites (Sites 1 and 5) for these novel, highly charged sulfated glycans, which were also confirmed by previously published reports. This work showed the structural features and key interactions driving ligand binding. A previous study predicted Site 2 to be a potential binding site, which was not observed here. The use of several molecular modeling approaches gave a comprehensive assessment. The detailed comparative study utilizing multiple modeling approaches is the first of its kind for novel glycan-SGP interaction characterization. This study provided insights into the key structural features of these novel glycans as they are considered for development as potential therapeutics.

Pancreaticoduodenectomy combined gastroduodenal collateral reconstruction and preservation due to median arcuate ligament syndrome: technical notes with two surgical cases report (with video)

INTRODUCTION

Pancreaticoduodenectomy in patients with CA stenosis due to median arcuate ligament often required carefully collateral pathways management to avoid hepatic ischemic complications.

CASES PRESENTATION

Case 1: A 63-year-old man was referred to our department because of jaundice with distal common bile duct tumor. Pancreaticoduodenectomy with left posterior SMA first approach and circumferential lymphadenectomy was performed. Case 2: A 48-year-old man was referred to our department because of right-upper-quadrant abdominal pain with Vater tumor. Laparoscopic pancreaticoduodenectomy with left posterior SMA first approach and circumferential lymphadenectomy was performed. Postoperatively, in all two cases, three-dimensional reconstruction images showed developed collateral pathways around the pancreatic head, and the CA was stenosis in 75% and 70% due to MAL, respectively. Intraoperatively, in all two cases, we confirmed poor blood flow in the common hepatic artery (CHA) by palpation and observation. So that in the first case, we have decided to proceed a no-touch technique of GDA segmental resection en bloc with the tumor and reconstructed with an end-to-end GDA anastomosis; in the second cases, we have decided to proceed gastroduodenal collateral preservation. When preserving these collateral pathways, we confirmed that the PHA flow remained pulsatile as an indicator that the blood flow was adequate.

CONCLUSION

Celiac axis stenosis was a rare but difficult-to-managed condition associated with pancreaticoduodenectomy. Collateral pathways management depends on variety of collateral pathways.

A Clinical Prediction Model to Predict Heparin Treatment Outcomes and Provide Dosage Recommendations: Development and Validation Study

BACKGROUND

Unfractionated heparin is widely used in the intensive care unit as an anticoagulant. However, weight-based heparin dosing has been shown to be suboptimal and may place patients at unnecessary risk during their intensive care unit stay.

OBJECTIVE

In this study, we intended to develop and validate a machine learning-based model to predict heparin treatment outcomes and to provide dosage recommendations to clinicians.

METHODS

A shallow neural network model was adopted in a retrospective cohort of patients from the Multiparameter Intelligent Monitoring in Intensive Care III (MIMIC III) database and patients admitted to the Peking Union Medical College Hospital (PUMCH). We modeled the subtherapeutic, normal, and supratherapeutic activated partial thromboplastin time (aPTT) as the outcomes of heparin treatment and used a group of clinical features for modeling. Our model classifies patients into 3 different therapeutic states. We tested the prediction ability of our model and evaluated its performance by using accuracy, the kappa coefficient, precision, recall, and the F1 score. Furthermore, a dosage recommendation module was designed and evaluated for clinical decision support.

RESULTS

A total of 3607 patients selected from MIMIC III and 1549 patients admitted to the PUMCH who met our criteria were included in this study. The shallow neural network model showed results of F1 scores 0.887 (MIMIC III) and 0.925 (PUMCH). When compared with the actual dosage prescribed, our model recommended increasing the dosage for 72.2% (MIMIC III, 1240/1718) and 64.7% (PUMCH, 281/434) of the subtherapeutic patients and decreasing the dosage for 80.9% (MIMIC III, 504/623) and 76.7% (PUMCH, 277/361) of the supratherapeutic patients, suggesting that the recommendations can contribute to clinical improvements and that they may effectively reduce the time to optimal dosage in the clinical setting.

CONCLUSIONS

The evaluation of our model for predicting heparin treatment outcomes demonstrated that the developed model is potentially applicable for reducing the misdosage of heparin and for providing appropriate decision recommendations to clinicians.

Edoxaban Plus Aspirin vs Dual Antiplatelet Therapy in Endovascular Treatment of Patients With Peripheral Artery Disease: Results of the ePAD Trial

Purpose: To report a randomized study that investigated the safety (risk of major bleeds) and potential efficacy of edoxaban, an oral anticoagulant that targets the major components of arterial thrombi, to prevent loss of patency following endovascular treatment (EVT). Methods: Between February 2012 and June 2014, 203 patients who underwent femoropopliteal EVT were randomized to receive aspirin plus edoxaban or aspirin plus clopidogrel for 3 months in the Edoxaban in Peripheral Arterial Disease (ePAD) study (ClinicalTrials.gov identifier NCT01802775). Randomization assigned 101 patients (mean age 68.0±10.4 years; 67 men) to the edoxaban group and 102 patients (mean age 66.7±8.6 years; 78 men) to the clopidogrel group. The primary safety endpoint was bleeding as classified by the TIMI (Thrombolysis in Myocardial Infarction) criteria and ISTH (International Society of Thrombosis and Hemostasis) criteria; the efficacy endpoint was the rate of restenosis/reocclusion. Results: There were no major or life-threatening bleeding events in the edoxaban group, while there were 2 major and 2 life-threatening bleeding events in the clopidogrel group by the TIMI criteria. By the ISTH classification, there was 1 major and 1 life-threatening bleeding event vs 5 major and 2 life-threatening bleeding events, respectively [relative risk (RR) 0.20, 95% confidence interval (CI) 0.02 to 1.70]. The bleeding risk was not statistically different with either treatment when assessed by TIMI or ISTH. Following 6 months of observation, there was a lower incidence of restenosis/reocclusion with edoxaban compared with clopidogrel (30.9% vs 34.7%; RR 0.89, 95% CI 0.59 to 1.34, p=0.643). Conclusion: These results suggest that patients who have undergone EVT have similar risks for major and life-threatening bleeding events with edoxaban and aspirin compared with clopidogrel and aspirin. The incidence of restenosis/reocclusion events, while not statistically different, was lower with edoxaban and aspirin, but an adequately sized trial will be needed to confirm these findings.

Fibulin-7, a heparin binding matricellular protein, promotes renal tubular calcification in mice

Ectopic calcification occurs during development of chronic kidney disease and has a negative impact on long-term prognosis. The precise molecular mechanism and prevention strategies, however, are not established. Fibulin-7 (Fbln7) is a matricellular protein structurally similar to elastogenic short fibulins, shown to bind dental mesenchymal cells and heparin. Here, we report that Fbln7 is highly expressed in renal tubular epithelium in the adult kidney and mediates renal calcification in mice. In vitro analysis revealed that Fbln7 bound heparin at the N-terminal coiled-coil domain. In Fbln7-expressing CHO-K1 cells, exogenous heparin increased the release of Fbln7 into conditioned media in a dose-dependent manner. This heparin-induced Fbln7 release was abrogated in CHO-745 cells lacking heparan sulfate proteoglycan or in CHO-K1 cells expressing the Fbln7 mutant lacking the N-terminal coiled-coil domain, suggesting that Fbln7 was tethered to pericellular matrix via this domain. Interestingly, Fbln7 knockout (Fbln7^-/-) mice were protected from renal tubular calcification induced by high phosphate diet. Mechanistically, Fbln7 bound artificial calcium phosphate particles (aCPP) implicated in calcification and renal inflammation. Binding was decreased significantly in Fbln7^-/- primary kidney cells relative to wild-type cells. Further, overexpression of Fbln7 increased binding to aCPP. Addition of heparin reduced binding between aCPP and wild-type cells to levels of Fbln7^-/- cells. Taken together, our study suggests that Fbln7 is a local mediator of calcium deposition and that releasing Fbln7 from the cell surface by heparin/heparin derivatives or Fbln7 inhibitory antibodies may provide a novel strategy to prevent ectopic calcification in vivo.

The Good the Bad and the Ugly of Glycosaminoglycans in Tissue Engineering Applications

High sulfation, low cost, and the status of heparin as an already FDA- and EMA- approved product, mean that its inclusion in tissue engineering (TE) strategies is becoming increasingly popular. However, the use of heparin may represent a naïve approach. This is because tissue formation is a highly orchestrated process, involving the temporal expression of numerous growth factors and complex signaling networks. While heparin may enhance the retention and activity of certain growth factors under particular conditions, its binding 'promiscuity' means that it may also inhibit other factors that, for example, play an important role in tissue maintenance and repair. Within this review we focus on articular cartilage, highlighting the complexities and highly regulated processes that are involved in its formation, and the challenges that exist in trying to effectively engineer this tissue. Here we discuss the opportunities that glycosaminoglycans (GAGs) may provide in advancing this important area of regenerative medicine, placing emphasis on the need to move away from the common use of heparin, and instead focus research towards the utility of specific GAG preparations that are able to modulate the activity of growth factors in a more controlled and defined manner, with less off-target effects.

Endothelial antigen assembly leads to thrombotic complications in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder initiated by antibodies against complexes between human platelet factor 4 (hPF4) and heparin. A better understanding of the events that initiate the prothrombotic state may improve approaches to antithrombotic management. Here, we visualized thrombus formation in an in vivo murine model and an endothelialized microfluidic system that simulate the pathogenesis of HIT. hPF4 released from platelets predominantly bound to peri-injury endothelium and formed HIT antigenic complexes that were dissociated by heparin. In mice expressing both hPF4+ and human platelet IgG Fc receptor IIA (FcγRIIA), infusion of the HIT-like monoclonal antibody KKO increased fibrin and platelet deposition at sites of injury, followed immediately by antigen formation on proximate endothelial cells. After a few minutes, HIT antigen was detected within the thrombus itself at the interface between the platelet core and the surrounding shell. We observed similar results in the humanized, endothelialized microfluidic system. hPF4 and KKO selectively bound to photochemically injured endothelium at sites where surface glycocalyx was reduced. These studies support the concept that the perithrombus endothelium is the predominant site of HIT antigen assembly. This suggests that disrupting antigen formation along the endothelium or protecting the endothelium may provide a therapeutic opportunity to prevent thrombotic complications of HIT, while sparing systemic hemostatic pathways.

Growth Differentiation Factor 5-Mediated Enhancement of Chondrocyte Phenotype Is Inhibited by Heparin: Implications for the Use of Heparin in the Clinic and in Tissue Engineering Applications

The highly sulfated glycosaminoglycan (GAG) heparin is widely used in the clinic as an anticoagulant, and researchers are now using it to enhance stem cell expansion/differentiation protocols, as well as to improve the delivery of growth factors for tissue engineering (TE) strategies. Growth differentiation factor 5 (GDF5) belongs to the bone morphogenetic protein family of proteins and is vital for skeletal formation; however, its interaction with heparin and heparan sulfate (HS) has not been studied. We identify GDF5 as a novel heparin/HS binding protein and show that HS proteoglycans are vital in localizing GDF5 to the cell surface. Clinically relevant doses of heparin (≥10 nM), but not equivalent concentrations of HS, were found to inhibit GDF5's biological activity in both human mesenchymal stem/stromal cell-derived chondrocyte pellet cultures and the skeletal cell line ATDC5. We also found that heparin inhibited both GDF5 binding to cell surface HS and GDF5-induced induction of Smad 1/5/8 signaling. Furthermore, GDF5 significantly increased aggrecan gene expression in chondrocyte pellet cultures, without affecting collagen type X expression, making it a promising target for the TE of articular cartilage. Importantly, this study may explain the variable (and disappointing) results seen with heparin-loaded biomaterials for skeletal TE and the adverse skeletal effects reported in the clinic following long-term heparin treatment. Our results caution the use of heparin in the clinic and in TE applications, and prompt the transition to using more specific GAGs (e.g., HS derivatives), with better-defined structures and fewer off-target effects.

Anti-activated factor II assay for monitoring unfractionated heparin in children: results of the HEARTCAT study

Essentials Unfractionated heparin has variable effects in children and therefore, monitoring is essential. A randomized controlled trial substudy investigating an anti-IIa assay in children was conducted. Anti-IIa values are lower in younger children, an effect more pronounced at low-dose heparin. Heparin effect on Xa and IIa is not equal, particularly in infants and after high-dose heparin.

SUMMARY

Background Unfractionated heparin (UFH) is used for the prophylaxis and treatment of thrombosis in children. Laboratory monitoring of UFH is needed to prevent over-anticoagulation or under-anticoagulation. Objectives To investigate the association between UFH dose and UFH effect as monitored with the anti-activated factor II (FIIa) assay, the relationship between anti-FIIa and anti-activated factor X (FXa) effects, and the influence of patient age and other factors on UFH effect. Patients and methods This was a randomized controlled trial in children during cardiac catheterization, comparing high-dose UFH (100 units kg-1 bolus) with low-dose UFH (50 units kg-1 bolus). Blood samples were drawn at baseline, and after 30 min, 60 min, and 90 min. For the purpose of this study, 49 children and 117 blood samples were evaluated. Results The anti-FIIa assay discriminated well between high-dose and low-dose UFH. Multiple regression demonstrated significant influences of UFH dose and age on anti-FIIa levels. Younger children had lower anti-FIIa levels than older children, an effect that was more pronounced with low-dose UFH. Anti-FXa/anti-FIIa ratios were equal with low-dose UFH. However, anti-FXa levels were relatively increased over anti-FIIa levels in infants and after high-dose UFH bolus administration. Conclusion The UFH effect on anti-FIIa levels is lower in infants than in older children. This influence of age appears to be dose-dependent, being more pronounced with low-dose UFH. Anti-FXa and anti-FIIa levels are not equal, particularly in infants and after high-dose UFH. Monitoring UFH solely with anti-FXa assays may not be sufficient in children, and the anti-FIIa assay may provide important complementary information.

Adult congenital heart disease nurse coordination: Essential skills and role in optimizing team-based care a position statement from the International Society for Adult Congenital Heart Disease (ISACHD)

BACKGROUND

Founded in 1992, the International Society for Adult Congenital Heart Disease (ISACHD) is the leading global organization of professionals dedicated to pursuing excellence in the care of adults with congenital heart disease (CHD) worldwide. Among ISACHD's objectives is to "promote a holistic team-based approach to the care of the adult with CHD that is comprehensive, patient-centered, and interdisciplinary" (http://www.isachd.org). This emphasis on team-based care reflects the fact that adults with CHD constitute a heterogeneous population with a wide spectrum of disease complexity, frequent association with other organ involvement, and varied co-morbidities and psychosocial issues.

METHODS

Recognizing the vital role of the adult CHD (ACHD) nurse coordinator (ACHD-NC) in optimizing team-based care, ISACHD established a task force to elucidate and provide guidance on the roles and responsibilities of the ACHD-NC. Acknowledging that nursing roles can vary widely from region to region based on factors such as credentials, scopes of practice, regulations, and local culture and tradition, an international panel was assembled with experts from North America, Europe, East Asia, and Oceania. The writing committee was tasked with reviewing key aspects of the ACHD-NC's role in team-based ACHD care.

RESULTS/CONCLUSION

The resulting ISACHD position statement addresses the ACHD-NC's role and skills required in organizing, coordinating, and facilitating the care of adults with CHD, holistic assessment of the ACHD patient, patient education and counseling, and support for self-care management and self-advocacy.

Monitoring unfractionated heparin in children: a parallel-cohort randomized controlled trial comparing 2 dose protocols

Monitoring unfractionated heparin (UFH) is crucial to prevent over- or under-anticoagulation. However, the optimal parameters for monitoring UFH in children are not well established. The study objectives were to investigate (1) the relationship between UFH dose and its anticoagulant effect as assessed by anti-Xa, activated partial thromboplastin time (aPTT) and activated clotting time (ACT); (2) other factors influencing UFH effect; (3) the agreement between the assays; and (4) the association between UFH effect and clinical outcome. HEARTCAT was a parallel-cohort randomized controlled trial comparing high-dose (100 U/kg bolus followed by age-based continuous infusion in randomized children) vs low-dose UFH (50 U/kg bolus) during cardiac catheterization in children. Blood samples were drawn before and after UFH administration at 30, 60, and 90 minutes. Four-hundred and two samples of 149 patients were evaluable. Anti-Xa, aPTT, and ACT all showed good discrimination between UFH doses. Regression models demonstrated the following determinants of UFH effect: UFH dose, age, baseline antithrombin (for anti-Xa), and baseline levels of aPTT and ACT, respectively. UFH effects were lower in infants compared with older children, which was more pronounced at low-dose than at high-dose UFH. Agreement between the 3 assays was poor. Most aPTT values were above therapeutic range or beyond measuring limit and thus of limited value for UFH monitoring. No association of UFH dose or effect with clinical outcome could be observed. In conclusion, all assays reflected a significant UFH dose-effect relationship, however, with poor agreement between the respective tests. The age-dependency of UFH effect was confirmed. Notably, the influence of age on UFH effect was dose-dependent.

Contemporary anticoagulation therapy in patients undergoing percutaneous intervention

The proper use of anticoagulants is crucial for ensuring optimal patient outcomes post percutaneous interventions in the cardiac catheterization laboratory. Anticoagulant agents such as unfractionated heparin, a thrombin inhibitor; low-molecular weight heparins, predominantly Factor Xa inhibitors; fondaparinux, a Factor Xa inhibitor and bivalirudin, a direct thrombin inhibitor have been developed to target various steps in the coagulation cascade to prevent formation of thrombin. Optimal anticoagulation achieves the correct balance between thrombosis and bleeding and is related to optimal outcomes with minimal complications. This review will discuss the mechanisms and appropriate use of current and emerging anticoagulant therapies used during percutaneous interventions.

Impact of anticoagulation on coronary flow in patients with non-ST elevation acute coronary syndrome

The effect of anticoagulation by heparin on patients with non-ST elevation acute coronary syndrome (NSTE-ACS), receiving early dual antiplatelet therapy, has not been fully evaluated. We classified 355 patients with NSTE-ACS according to the adequacy of anticoagulation (percentage of low activated partial thromboplastin time [APTT] level). The 6-hour APTT level was optimal in only 23.1% of the patients treated with unfractionated heparin. The rate of poor preprocedural coronary blood flow (thrombolysis in myocardial infarction grade <3, 39.1%, 30.5%, 30.3%, and 33.9% in the 100% low-, 99%∼50% low-, 49%∼1% low-, and 0% low-APTT group, respectively, P = .632) and bleeding events did not differ between the groups. Instead, in multivariate analysis, the diagnosis of myocardial infarction was the only independent predictor of poor coronary flow. For bleeding events, the usage of glycoprotein IIb/IIIa inhibitor appeared to be a sole risk factor. In conclusion, inadequate preprocedural anticoagulation was not associated with adverse outcomes in patients with NSTE-ACS treated with dual antiplatelet agents.

Heparin inhibits angiotensin II-induced vasoconstriction on isolated mouse mesenteric resistance arteries through Rho-A- and PKA-dependent pathways

Heparin is commonly used to treat intravascular thrombosis in children undergoing extracorporeal membrane oxygenation or cardiopulmonary bypass. These clinical circumstances are associated with elevated plasma levels of angiotensin II (Ang II). However, the mechanisms by which heparin modulates vascular reactivity of Ang II remain unclear. We hypothesized that heparin may offset Ang II-induced vasoconstriction on mesenteric resistance arteries through modulating the Rho-A/Rho kinase pathway. Vascular contractility was studied by using pressurized, resistance-sized mesenteric arteries from mice. Rho-A activation was measured by pull-down assay, and myosin light chain or PKA phosphorylation by immunoblotting. We found that heparin significantly attenuated vasoconstriction induced by Ang II but not that by KCl. The combined effect of Ang II with heparin was almost abolished by a specific Rho kinase inhibitor Y27632. Ang II stimulated Rho-A activation and myosin light chain phosphorylation, both responses were antagonized by heparin. Moreover, the inhibitory effect of heparin on Ang II-induced vasoconstriction was reversed by Rp-cAMPS (cAMP-dependent PKA inhibitor), blunted by ODQ (soluble guanylate cyclase inhibitor), and mimicked by a cell-permeable cGMP analogue, 8-Br-cGMP, but not by a cAMP analogue. PKC and Src kinase were not involved. We conclude that heparin inhibits Ang II-induced vasoconstriction through Rho-A/Rho kinase- and cGMP/PKA-dependent pathways.

Heparin dosing is associated with diffusion weighted imaging lesion load following aneurysm coiling

BACKGROUND AND PURPOSE

Diffusion weighted imaging (DWI) may be used to evaluate post-coiling ischemia. Heparinization protocols for cerebral aneurysm coiling procedures differ among operators and centers, with little literature surrounding its effect on DWI lesions. The goal of this study was to determine which factors, including heparinization protocols, may affect DWI lesion load post-coiling.

MATERIALS AND METHODS

A review of 135 coiling procedures over 5 years at our centre was performed. Procedural data including length of procedure, number of coils used, stent or balloon assistance and operators were collected. Procedures were either assigned as using a bolus dose (>2000 U at any one time) or small aliquots of heparin (≤2000 U). Postprocedure DWI was reviewed and lesions were classified as small (< 5mm), medium (5-10 mm) or large (>10 mm). The cases were then classified into group 1 (≤5 small lesions) or group 2 (>5 small lesions or ≥1 medium or large lesion). Multivariate regression of the procedural variables for the two groups was calculated. A p value of <0.05 was considered significant.

RESULTS

There were 78 procedures in group 1 and 57 procedures in group 2. Patients who received small aliquots (n=37) versus boluses of heparin (n=98) intraprocedurally had significantly greater frequency and size of DWI lesions (p=0.03). None of the other procedural variables was found to impact on lesion load.

CONCLUSIONS

More substantial DWI lesions were associated with small aliquots of heparin dosage compared with bolus doses. Heparin boluses should be preferentially administered during aneurysm coiling.

Venous thromboembolism following microsurgical breast reconstruction: an objective analysis in 225 consecutive patients using low-molecular-weight heparin prophylaxis

BACKGROUND

Free flap breast reconstruction involves major risk factors for postsurgical venous thromboembolism. The main study objectives were (1) to estimate objectively the incidence of symptomatic and asymptomatic lower extremity deep vein thrombosis in patients who received postoperative thromboprophylaxis after free flap breast reconstruction, (2) to evaluate the safety of low-molecular-weight heparin postoperatively, and (3) to assess the incidence of symptomatic pulmonary embolism or sudden death.

METHODS

A cohort study of 225 consecutive patients who underwent abdominally based free flap breast reconstruction at a single cancer center was conducted. The postoperative thromboprophylaxis regimen was based on the American College of Chest Physicians guidelines. A study group of 118 patients systematically underwent bilateral lower extremity duplex ultrasound before hospital discharge to assess objectively the status of the lower extremity deep venous system. A retrospective cohort of 107 women who were not systematically screened for deep vein thrombosis was used for comparison.

RESULTS

The incidence of postoperative deep vein thrombosis confirmed by duplex ultrasound was 3.4 percent in the study group, all events being clinically silent. Bleeding complications in the entire patient sample were estimated at 5.3 percent. Partial flap loss and total flap loss rates were 2.7 and 1.9 percent, respectively. No venous thromboembolism event was diagnosed in the control group.

CONCLUSIONS

This report shows that the objective incidence of deep vein thrombosis was 3.4 percent within 5 postoperative days in this patient population. The authors' findings support the use of triple thromboprophylaxis and demonstrate that low-molecular-weight heparin is a safe and effective method for prevention of venous thromboembolism in this population.

Dose-escalation study of the pharmacokinetics and pharmacodynamics of rivaroxaban in healthy elderly subjects

OBJECTIVE

The aim of this study was to investigate the pharmacokinetics and pharmacodynamics of rivaroxaban--a novel, oral, direct Factor Xa (FXa) inhibitor--in healthy elderly subjects.

RESEARCH DESIGN AND METHODS

In this single-centre, single-blind, placebo-controlled, parallel-group, dose-escalation study, 48 subjects (aged 60-76 years) were randomized to receive a single oral dose of 30, 40 or 50 mg of rivaroxaban or placebo.

RESULTS

Rivaroxaban was absorbed rapidly, reaching peak plasma concentration (C(max)) 4 h after dosing in all groups. Bioavailability, in terms of the area under the plasma concentration-time curve (AUC) and C(max), increased slightly (less than dose proportionally) after administration of rivaroxaban 40 mg compared with 30 mg, but was not increased further with rivaroxaban 50 mg. Rivaroxaban pharmacodynamic effects (inhibition of FXa activity and prolongation of prothrombin time, activated partial thromboplastin time and HepTest) all showed a similar pattern, with maximum inhibition of FXa activity increasing from 68% after rivaroxaban 30 mg to 75% after 40 mg and no further increase with the 50 mg dose. Most adverse events were mild; observed rates were less than placebo for the 30 and 40 mg dose groups, and similar to placebo for 50 mg. No differences were found between male and female subjects. Effects of rivaroxaban doses above 50 mg were not investigated in this study.

CONCLUSIONS

Each single dose of rivaroxaban was well tolerated, with predictable pharmacokinetics and pharmacodynamics at doses up to 40 mg, and provided effective anticoagulation in healthy elderly subjects. Adverse events were somewhat elevated in the 50 mg group, but given the small sample size, no specific conclusions can be drawn about this dosing level.

The anti-inflammatory effects of heparin and related compounds

Heparin is a glycosaminoglycan well known for its anticoagulant properties. In addition, heparin possesses anti-inflammatory effects. Although the mechanisms responsible for the anticoagulant effects of heparin are well understood, those underlying its anti-inflammatory effects are not. This review presents some of the evidence from clinical and animal studies supporting an anti-inflammatory role for heparin and heparin-related derivatives. Potential mechanisms by which heparin can exert its anti-inflammatory effects are discussed. The clinical use of heparin as an anti-inflammatory agent has been held back by the fear of bleeding. Development of nonanticoagulant heparins or heparin derivatives should mitigate this concern.

Molecular weight dependent tissue factor pathway inhibitor release by heparin and heparin oligosaccharides

Heparin and low molecular weight heparins exert their vascular effects by mobilizing tissue factor pathway inhibitor (TFPI) from the vascular endothelium into the blood circulation. We compared the influence of molecular weight on the TFPI release by heparin and its fractions in a non-human primate model. Primates were treated with unfractionated heparin, a low molecular weight heparin (gammaparin), or a heparin-derived oligosaccharide mixture (C3). Endothelial TFPI release was determined using both immunologic and functional assays. After intravenous administration, all agents significantly increased TFPI levels (p<0.05) in a dose dependent manner. The increase produced by unfractionated heparin and gammaparin was greater than that by C3 at an equal dosage (p<0.05). With subcutaneous injection, all agents produced less TFPI release. Repeated administration of heparin-derived oligosaccharides gradually increased TFPI release. A 1.89 fold increase in TFPI levels was observed 4 days after C3 treatment (2.5 mg/kg). Our findings indicated that TFPI release is dependent on the molecular weight of heparin and its derivatives. Heparin oligosaccharides exert their vascular effects through increased TFPI release after long-term repeated administration.

Mechanism of antithrombotic effect of heparin and antithrombin in balloon-injured arteries

The mechanism of the antithrombotic effects of heparin and the synthetic antithrombin agent argatroban was evaluated in a dog model. Thrombus formation following balloon injury was evaluated by angioscopy in the right iliac arteries of 20 dogs to serve as a control. After the evaluation of the growth of thrombus on the control side, heparin (200 U/kg) or argatroban (0.2 mg/kg) was infused intravenously, and the distal site of the contralateral left iliac artery was injured in the same manner. At 30 to 120 min before the final examination, the proximal site of the left iliac artery also was injured. After antithrombotic drug infusion, the percent angioscopic stenosis at the distal site was much lower (P<0.0001) than that of the control site (mean stenosis index: 0.67 in heparin vs. 3.8 in control, and 0.25 in argatroban vs. 4.3 in control); however, thrombus formation was observed at the proximal site. With local delivery of a low dose of either antithrombotic drug (n=10), an antithrombotic effect was maintained until 4 h after the infusion. A very weak fluorescence of FITC-heparin was detected at the injured artery 2 h after infusion. In a shunt experiment involving 5 dogs, carotid arteries were injured and incubated in oxygenated Krebs--Henseleit solution before auto grafting into the femoral artery. At 2 h after the grafting, no thrombus was formed in the grafted vessels incubated for 4 h, but was formed in those incubated for 10 min. These results indicate that the relatively long antithrombotic effect of these drugs may be due to a local drug effect at the injured artery, as well as the recovery of the anti-thrombogenicity of the injured artery.

An international survey of current practice in the laboratory assessment of anticoagulant therapy with heparin

AIMS

We conducted a survey of laboratory practice for assessment of heparin anticoagulant therapy by participants of the Royal College of Pathologists of Australasia Quality Assurance Program (RCPA QAP).

METHODS

A questionnaire was sent to 646 laboratories enrolled in the Haematology component of the QAP, requesting details of tests used for monitoring heparin therapy.

RESULTS

Seventy laboratories (10.8%) returned results that indicated that they performed laboratory monitoring of heparin therapy. Most laboratories (69/70 = 98.6%) use the activated partial thromboplastin time (APTT) to monitor unfractionated heparin, with eight (11.4%) also using the APTT for monitoring low molecular weight (LMW) heparin. Five (7.1%) laboratories use the thrombin time (TT) test to help monitor heparin therapy and 37 (52.9%) laboratories use an anti-Xa assay to monitor heparin (either LMW or unfractionated). Normal reference ranges (NRR) for APTT differed considerably between laboratories, even those using the same reagent. Therapeutic ranges (TR) also differed considerably between laboratories, for both APTT and the anti-Xa assay. Laboratory differences in NRR and TR using the same reagents could only be partly explained by the use of different instrumentation.

CONCLUSIONS

There is a large variation in current laboratory practice relating to monitoring of heparin anticoagulant therapy. This finding is similar to that of a similar survey conducted by the RCPA QAP almost a decade ago. This study suggests that better standardisation is still required for laboratory monitoring of heparin therapy.

Anticoagulant therapy in Japanese patients with mechanical mitral valves

There are no guidelines for the optimal therapeutic range of anticoagulant therapy in Japanese patients with mechanical heart valves. A total of 214 patients were followed retrospectively after mitral mechanical valve replacement (mean duration of follow-up, 4.8 years; total duration of follow-up, 1,027 patient-years). The target range of the international normalized ratio (INR) for oral anticoagulation was between 1.5 and 2.5. For all patients 10,416 measurements of the INR were obtained during the follow-up period and approximately 76% of the intensity measurements were within the target range. Thromboembolism occurred in 8 patients (0.8 per 100 patient-years) and major bleeding in 5 patients (0.5 per 100 patient-years). There was no correlation between the distribution of the INR and the occurrence of thromboembolic or bleeding complications. In the univariate analysis of the various risk factors, patients who had a tilting valve or did not receive antiplatelet therapy had an increased risk of thromboembolism. However, there were no risk factors with respect to bleeding complications. A target range of 1.5 to 2.5 INR appears to be the optimal range and is safe for thromboembolism or bleeding complications. Thromboembolism may be reduced by additional antiplatelet therapy, and a tilting valve needs more intense anticoagulation.