Development and application of health outcome descriptors facilitated decision-making in the production of practice guidelines

OBJECTIVE

Stakeholders involved in developing recommendations need to have a common understanding of health outcomes and the perspective of affected individuals. In this paper we report on the development and application of health outcome descriptors (HODs) to inform decision-making by panels developing guideline recommendations.

STUDY DESIGN AND SETTING

Ten American Society of Hematology guideline panels addressing the management of venous thromboembolism developed HODs, rated their importance and health utility, applied them to prioritize outcomes, and to balance potential benefits and harms to formulate recommendations.

RESULTS

It was feasible to involve 18 panelists in developing 127 HODs. There was high agreement (82%) across the ten panels about outcomes perceived as critical or important for decision-making. Panelists' utility ratings of the outcomes were strongly correlated with panelists' outcome importance ratings (Pearson's r=-0.88). HODs were incorporated into Grading of Recommendations Assessment, Development and Evaluation (GRADE) evidence-to-decision (EtD) frameworks to support a shared understanding of health outcomes in panel deliberations.

CONCLUSION

HODs serve as a valuable tool to promote an explicit, common understanding of health outcomes during clinical guideline development and across different stakeholders. They are helpful across multiple steps of guideline development to facilitate panels' judgements, aiming to avoid variable implicit interpretations of health outcomes.

Is intravenous thrombolysis safe for acute ischemic stroke patients taking warfarin with INR 1.9?: A case report

INTRODUCTION

Intravenous thrombolysis is not suitable for patients undergoing oral anticoagulants therapy, with INR > 1.7 or PT > 15 s. We described a case of intravenous thrombolysis in a patient with INR 1.9.

PATIENT CONCERNS

A 66-year-old female patient was diagnosed with acute appendicitis complicated with atrial fibrillation. Seven days after admission, the patient suffered mixed aphasia with right limb asthenia. The NIHSS score was 11 points. and early infarction and hemorrhagic manifestations were not found in the emergency head CT. Thirty minutes after the onset of symptoms, NIHSS of patient increased from 11 to 14, but the INR was 1.92.

DIAGNOSIS

Acute ischemic stroke.

INTERVENTIONS

The IT therapy was recommended and all the therapy related risks were explained to the patient's parents. Briefly, the patient was given rTPA 38.5 mg. In addition to intravenous thrombolysis, VitK1 40 mg was simultaneously administered.

OUTCOME

The patient's symptoms of drowsiness were improved. After 24 hours, all symptoms were stabilized with NIHSS of 2 points, there was a slight language obstruction, and no hemorrhagic transformation in head CT. Three months later, the review showed MRS score of 0, and the patient could take care of herself in daily life.

CONCLUSION

The clinical guidelines are still the main reference for guiding clinical practice, and the main thrombolytic standards and contraindications for treatment still need to be conformed. On this basis, for individualized patients, clinicians must accurately judge the cause of acute stroke, to make optimal choice, reduce disability and mortality, and improve quality of life of patients.

Increased risk of first-ever stroke in younger patients with atrial fibrillation not recommended for antithrombotic therapy by current guidelines: a population-based study in an East Asian cohort of 22 million people

OBJECTIVE

To assess the risk of first-ever ischemic stroke in younger patients with atrial fibrillation (AF) who have none of the CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, previous stroke/transient ischemic attack, vascular disease, age 65-74 years, sex category [female sex]) risk factors (excluding female sex) by using the National Health Insurance research database in Taiwan.

PATIENTS AND METHODS

From 22,842,778 insured people, we identified 24,612 hospitalized patients with newly diagnosed AF between January 1, 2002, and December 31, 2004, as the AF group and randomly selected 98,448 age- and sex-matched persons without AF as the non-AF group. Both groups were followed up until December 31, 2010, to estimate ischemic stroke incidences in relation to other stroke risk factors.

RESULTS

During a follow-up period of 89,468 person-years, the stroke rate was higher in patients with AF than in those without AF (5.79 per 100 person-years vs 2.25 per 100 person-years). The higher prevalence of CHA2DS2-VASc comorbidities (heart failure, hypertension, diabetes, coronary artery disease, and peripheral artery disease) in patients with AF further increased the stroke risk. In 790 patients with AF aged 30 to 55 years who had none of the CHA2DS2-VASc comorbidities at baseline and retained a "low risk," that is, those with a CHA2DS2-VASc score of 0 in men and 1 in women during follow-up, the stroke rate remained considerably higher than that in their non-AF counterparts (1.00 per 100 person-years vs 0.25 per 100 person-years), with a sex-adjusted hazard ratio of 4.09 (95% CI, 2.97-5.62).

CONCLUSION

This study finds an increased risk of stroke in younger patients with AF who are not recommended for prevention of thromboembolism by current guidelines. Better stroke risk stratification tools are needed to prioritize younger patients with AF for thromboprophylactic therapy in this population.

Periprocedural management of antithrombotic therapy in hospitalized patients

The management of antithrombotic medications in patients requiring invasive procedures is a common problem in hospital medicine, for which there is limited evidence to guide clinical decision making. Existing guidelines do not address many hospital-based procedures and have not kept pace with the introduction of newer antiplatelet and anticoagulant medications. This article provides a conceptual framework for the periprocedural management of antithrombotic therapy, with a focus on the procedures that hospitalists are most likely to perform and the pharmacology of the common and newer antithrombotic medications.

Safety of protocol violations in acute stroke tPA administration

BACKGROUND

Intravenous (IV) tissue plasminogen activator remains the only approved therapy for acute ischemic stroke (AIS) in the United States; however, less than 10% of patients receive treatment. This is partially because of the large number of contraindications, narrow treatment window, and physician reluctance to deviate from these criteria.

METHODS

We retrospectively analyzed consecutive patients who received IV thrombolysis at our stroke center for National Institute of Neurological Disorders and Stroke (NINDS) protocol violations and rates of symptomatic intracerebral hemorrhage (sICH). Other outcome variables included systemic hemorrhage, modified Rankin Scale at discharge, and discharge disposition.

RESULTS

A total of 212 patients were identified in our stroke registry between 2009 and 2011 and included in the analysis. Protocol violations occurred in 76 patients (36%). The most common violations were thrombolysis beyond 3 hours (26%), aggressive blood pressure management (15%), elevated prothrombin time (PT) or partial thromboplastin time (PTT) (6.6%), minor or resolving deficits (4.2%), unclear time of onset (3.9%), and stroke within 3 months (3%). There were no significant differences in any of the safety outcomes or discharge disposition between patients with or without protocol violations. Controlling for age, National Institutes of Health Stroke Scale on admission, and glucose on admission, there was no significant increase in sICH (odds ratio: 3.8; 95% confidence interval: .37-38.72) in the patients who had protocol violations.

CONCLUSIONS

Despite more than one third of patients receiving thrombolysis with protocol violations, overall rates of hemorrhage remained low and did not differ from those who did not have violations. Our data support the need to expand access to thrombolysis in AIS patients.

Antithrombotic therapy for cervical artery dissection

Antithrombotic therapy in patients with cervical artery dissection (CAD) is empiric rather than evidence based. The routine use of anticoagulants in each CAD patient cannot be recommended. A randomized controlled trial comparing antiplatelets with anticoagulation is clearly needed. However, due to the large sample size, which is required to gather meaningful results, such a trial is a huge venture. Thus, the matter of antithrombotic treatment in CAD is not expected to be solved in the near future. What should clinicians do in the meantime? There are several pathophysiological arguments in favor as well as against anticoagulants or antiplatelets. Until more data are available, it is our personal recommendation that treatment decisions should be geared to several clinical and paraclinical features of individual patients. The chapter compiles putative arguments in favor versus against immediate anticoagulation and may be helpful for individually tailored antithrombotic treatment decisions in CAD patients.

Thrombolysis for lower extremity deep venous thrombosis

Catheter-directed thrombolysis (CDT) has been proposed as an alternative mode of therapy to anticoagulation in patients with massive, symptomatic deep vein thrombosis of the extremity. The major goal of therapy is to rapidly restore venous blood flow, reduce the pain and edema of the extremity, preserve venous valve function, and reduce chronic symptoms related to chronic venous hypertension (postthrombotic syndrome). In patients with iliofemoral deep venous thrombosis (DVT) standard angiographic techniques are used to instrument a lower extremity vein (popliteal) and venography is performed followed by catheter-directed infusion of a plasminogen activator directly into the thrombus. Following lytic infusion, the interventionalist must evaluate the venous drainage to determine if there is an anatomic lesion that requires further endovascular treatment (eg, iliac vein compression syndrome). Posttreatment therapy usually consists of warfarin therapy and venous compression stockings for at least 3 to 6 months. The purpose of this article is to review the technical approach used in treating iliofemoral DVT and highlight the hurdles that face interventionalists in attempting to broaden this procedure to most types of lower extremity DVT.

Low-molecular-weight heparin as bridging anticoagulation during interruption of warfarin: assessment of a standardized periprocedural anticoagulation regimen

BACKGROUND

The treatment of patients at increased risk for arterial thromboembolism who require temporary interruption of warfarin sodium therapy is a common clinical problem. We investigated the efficacy and safety of a standardized periprocedural anticoagulation regimen with low-molecular-weight heparin.

METHODS

We studied 650 consecutive patients with a mechanical heart valve, chronic atrial fibrillation, or embolic stroke who required interruption of warfarin therapy because of an invasive procedure. Warfarin was stopped 5 or 6 days before the procedure, and patients received subcutaneous dalteparin sodium, 100 IU/kg twice daily, starting 3 days before the procedure. The risk of postprocedural bleeding determined postprocedural anticoagulant management. In patients undergoing a non-high-bleeding-risk procedure who had adequate postprocedural hemostasis, warfarin was resumed on the evening of the procedure, and dalteparin sodium, 100 IU/kg twice daily, was resumed on the next day and continued until the international normalized ratio was 2.0 or more. If postprocedural hemostasis was not secured, the resumption of dalteparin was delayed. In patients undergoing a high-bleeding-risk procedure, warfarin was resumed on the evening of the procedure, but dalteparin was not given after the procedure.

RESULTS

Patients were followed up during the preprocedural and postprocedural period for a mean of 13.8 days (range, 10-18 days). In 542 patients who underwent a non-high-bleeding-risk procedure, there were 2 thromboembolic events (0.4%), 4 major bleeding episodes (0.7%), and 32 episodes of increased wound-related blood loss that precluded postprocedural dalteparin administration (5.9%). In 108 patients who underwent a high-bleeding-risk procedure, there were 2 deaths (1.8%) possibly due to thromboembolism and 2 major bleeding episodes (1.8%).

CONCLUSIONS

In patients at increased risk for arterial thromboembolism who require temporary interruption of warfarin therapy, a standardized periprocedural anticoagulant regimen with low-molecular-weight heparin is associated with a low risk of thromboembolic and major bleeding complications.

Prevention of venous thromboembolism in orthopedic surgery with vitamin K antagonists: a meta-analysis

BACKGROUND

The benefit-to-risk ratio of vitamin K antagonists (VKA), relative to active comparators, especially low-molecular-weight heparins (LMWH), for preventing venous thromboembolism in patients undergoing major orthopedic surgery is debated.

OBJECTIVES

We performed a meta-analysis of all randomized trials in orthopedic surgery comparing adjusted doses of VKA to control treatments.

PATIENTS AND METHODS

An exhaustive literature search, both manual and computer-assisted, was performed. Studies were selected on the basis of randomization procedure (VKA vs. a control group). At least one of the following outcome measures was to be evaluated: deep vein thrombosis (DVT), pulmonary embolism (PE), death, major hemorrhage or wound hematoma. Four reviewers assessed each article to determine eligibility for inclusion and outcome measures.

RESULTS

VKAs were more effective than placebo or no treatment in reducing DVT [567 patients, relative risk (RR) = 0.56, 95% confidence interval (CI) 0.37, 0.84, P < 0.01] and clinical PE (651 patients, RR = 0.23, 95% CI 0.09, 0.59, P < 0.01). These results were obtained at the cost of a higher rate of wound hematoma (162 patients, RR = 2.91, 95% CI 1.09, 7.75, P = 0.03). VKAs were also more effective than intermittent pneumatic compression (534 patients, RR = 0.46, 95% CI 0.25, 0.82, P = 0.009) in preventing proximal DVT. In contrast, VKAs were less effective than LMWH in preventing total DVT and proximal DVT (9822 patients, RR = 1.51, 95% CI 1.27, 1.79, P < 0.001; and 6131 patients, RR = 1.51, 95% CI 1.04, 2.17, P = 0.028, respectively). The differences between VKA and LMWH in major hemorrhage and wound hematoma were not significant.

CONCLUSIONS

In patients undergoing major orthopedic surgery, VKAs are less effective than LMWH, without any significant difference in the bleeding risk.

Randomized clinical stroke trials in 2003

Randomized clinical stroke trials published during 2003 dealt with what impact treatment of stroke risk factors have on reducing future strokes. Treatment of hypertension and hyperlipidemia, and atrial fibrillation with a new anticoagulant, were confirmed to be beneficial. Treatment with female hormones was not beneficial. A potentially important study indicated that donepezil is a useful treatment for dementia in people who have had strokes.

Call-to-needle times for thrombolysis in acute myocardial infarction in Victoria

OBJECTIVE

To determine the proportion of patients in Victoria treated within the British Heart Foundation 90-minute call-to-needle (CTN) time benchmark for thrombolysis of ST-elevation myocardial infarction (STEMI), and to validate the British Heart Foundation 90-minute benchmark with respect to mortality.

DESIGN

Cohort study.

SETTING

20 hospitals and two ambulance services in the State of Victoria, Australia.

PARTICIPANTS

1147 patients with STEMI transported to hospital by ambulance and eligible for thrombolysis.

MAIN OUTCOME MEASURES

CTN time, and in-hospital mortality.

RESULTS

Median CTN time was 83 minutes (mean, 93.2 min; range, 29-894 min). Median door-to-needle (DTN) time was 37 minutes (mean, 46.5 min; range, 0-853 min). 61% of patients received thrombolysis within the 90-minute benchmark. Patients with CTN times > 90 minutes had an increased risk of dying (relative risk, 1.8; 95% CI, 1.3-2.7). Factors associated with CTN time < 90 minutes were lower DTN time, prior notification of the receiving hospital and transport time less than 20 minutes.

CONCLUSION

The British Heart Foundation CTN time benchmark is being met for 61% of eligible STEMI patients in Victoria. Strategies to reduce CTN time should be region-specific, and should include attempts to reduce DTN and to enhance ambulance-hospital communication. Prehospital thrombolysis may be appropriate for some regions.

Isolation of endogenous anticoagulant N-sulfated glycosaminoglycans in human plasma from healthy subjects

Endogenous N-sulfated glycosaminoglycans (GAGs) comigrating with standard heparin and sensitive to nitrous acid treatment were isolated from plasma of healthy donors. The amount of these compounds was 7-10 microg/ml, and activated partial thromboplastin time, anti-Xa and anti-IIa activities were similar to those of standard heparin of high molecular mass. Analysis with gradient PAGE of the putative endogenous heparin showed a mean molecular mass of 12 kD. These N-sulfated GAGs could be isolated only after removal of binding peptides that impaired purification by ion-exchange chromatography. We used SDS-PAGE as a tool to separate peptides from endogenous GAGs. N-sulfated GAGs exited the gel before peptides when the electrophoresis was overrun. Endogenous GAGs could be recovered by ion-exchange chromatography of the SDS-PAGE buffer, 'free' from associating peptides. These results strongly support the hypothesis that endogenous heparin is associated in vitro with a variety of proteins and that this association could be responsible for modification of both heparin and protein activities.

The outcome of ambulatory DVT management using a multidisciplinary approach

Low molecular weight heparins (LMWHs) have been demonstrated to be at least as safe and effective as unfractionated heparin (UFH) in the initial management of deep vein thrombosis (DVT). However, the effectiveness of using LMWH in the ambulatory management of DVT in a 'real-life' setting has yet to be evaluated. This multicentre retrospective study involving 697 patients considers the outcome data of patients under- going ambulatory DVT treatment with tinzaparin (Innohep(R), Leo Pharmaceuticals, Risborough, Buckinghamshire, UK). During the 6 months following presentation, 17 (2.5%) patients had confirmed thromboembolic complications, of which 14 occurred subsequent to the initial LMWH treatment phase ('late'). There were no deaths in this group. Bleeding complications were reported in 23 (3.4%) patients, with 13 of these being classified as 'late'. Of these, two events were considered major resulting in hospitalization and death. Hospitalization for all causes was 6.8% (45 patients) with 32 patients being admitted for thromboembolic or bleeding complications. Overall mortality was 6.7%. These results compare favourably with published clinical trial data. This study demonstrates that ambulatory treatment of proven DVT with LMWH is both safe and effective.

Antithrombogenic polymer alloy composed of 2-methacryloyloxyethyl phosphorylcholine polymer and segmented polyurethane

To evaluate the antithrombogenicity of a new polymeric biomaterial in vivo, a polymer alloy tube composed of poly[2-methacryloyloxyethyl phosphorylcholine(MPC)-co-2-ethylhexyl methacrylate](PMEH) polymer and a segmented polyurethane (SPU) was prepared by a solvent evaporation method on a Teflon rod from a homogeneous solution containing both the PMHE and SPU. The composition of the PMEH vs the SPU was 10 wt%. The inner and outer surfaces of the polymer alloy tubing were characterized by X-ray electron spectroscopic (XPS) measurements. The MPC units were located on the inner surface of the polymer alloy tubing rather than the outer surface. After immersion in aqueous media, a higher concentration of the MPC units was observed on both surfaces. Selective staining of the MPC units with osmium tetraoxide was carried out to observe the morphology of the PMEH domain on the surface of the polymer alloy. There were large-sized PMEH domains on the inner surface of the tubing but small-sized domains were found on the outer surface. This result was in good agreement with the XPS results. Blood compatibility of the polymer alloy was evaluated by observation of fibrinogen adsorption and platelet adhesion from human plasma. A lot of fibrinogen was adsorbed and many platelets adhered to the inner surface of the original SPU tubing. On the other hand, the PHEH/SPU polymer alloy tubing suppressed these adsorptions and adhesions. When the PMEH/SPU polymer alloy tubing was implanted into a rabbit's artery, thrombus could not be observed even after a 7-day implantation but the original SPU tubing was almost totally occluded only after a 90-min implantation due to serious thrombus deposition on the surface. These results clearly indicated that the PMEH in the SPU matrix acted as an antithrombus reagent by suppression of protein adsorption and platelet adhesion and activation. Particularly, the MPC units played a significant role in this function.

Measurement of hematological, clinical chemistry, and infection parameters from hirudinized blood collected in universal blood sampling tubes

Hirudin, the anticoagulatory polypeptide of the leech Hirudo medicinalis, strongly inhibits thrombus formation by specifically interacting with thrombin. For diagnostic purposes, hirudin should be superior to other anticlotting compounds because it only minimally alters the mineral, protein, and cellular blood constituents. To test this hypothesis, hirudinized and routinely processed venous blood from 80 healthy volunteers and patients was subjected to a variety of automated blood tests. A strong correlation was found between the results of automated complete blood counts obtained from K(2)-ethylenediaminetetraacetic acid (EDTA) anticoagulated and hirudinized blood (1000 antithrombin units [ATU] hirudin/ml). In addition, clinical chemistry and serological infection parameters (asparlat amintransferase [ASAT], lactate dehydrogenase [LDH], sodium, and so on, and antibodies against hepatitis B and C and human immunodeficiency virus [HIV]1/2, respectively) correlated well when measured in serum as compared with hirudinized plasma. Contrary to single clotting factors, global coagulation parameters (activated partial thromboplastin time [aPTT], prothrombin time [PT]) could not be measured in hirudinized blood. Recombinant hirudin neither interfered with immunophenotyping of mononuclear cells using FACScan analysis, nor did it alter the detection of Wilms' tumor gene expression by RT-PCR technology even at high doses (5000 ATU hirudin). Thus, a hirudin-containing blood sampling tube can be designed as a universal blood sampling tube (UBT) for testing the majority of diagnostic blood parameters.

Heparins and venous thromboembolism: current practice and future directions

Unfractionated heparin (UFH) in adjusted doses and low-molecular-weight heparins (LMWH) in fixed doses are the chosen therapy for the initial treatment of venous thromboembolism. The use of UFH protocols ensures that virtually all patients will promptly achieve the therapeutic range for the activated partial thromboplastin time. However, proper use of UFH requires considerable expertise, can cause inconvenience and has limitations. Unmonitored therapy with subcutaneous LMWH is at least as effective and safe as adjusted-dose UFH, is associated with a considerable reduction of mortality in cancer patients, and permits the treatment of suitable patients in an outpatient setting. LMWH in high prophylactic doses is more effective than UFH and oral anticoagulants for prevention of postoperative venous thrombosis in major orthopedic surgery. Whether thromboprophylaxis should be continued for a few additional weeks after hospital discharge is controversial. LMWH and UFH are equally effective for prevention of postoperative deep-vein thrombosis in cancer patients. In a recent controlled randomized trial, enoxaparin in high prophylactic doses was an effective and safe measure of thromboprophylaxis in ordinary bedridden patients. The efficacy and safety of pentasaccharide (the smallest antithrombin binding sequence of heparin) in the treatment and prevention of venous thromboembolic disorders is currently under investigation.

Anti-GPIIb/IIIa drugs: current strategies and future directions

Three platelet glycoprotein (GP) IIb/IIIa receptor antagonists have been approved as adjunctive therapy to decrease the ischemic complications of percutaneous coronary interventions (PCI) and/or unstable angina. They include the chimeric murine/human monoclonal antibody 7E3 Fab fragment (abciximab), a cyclic heptapeptide based on the KGD amino acid sequence (eptifibatide), and a nonpeptide mimetic of the RGD sequence (tirofiban). The agents are very effective in providing both short-term and long-term benefit after PCI, and one agent has also demonstrated a progressive long-term mortality benefit. The long-term mortality benefit is highly cost-effective when compared to other medical interventions. The benefits in treating unstable angina without PCI are less dramatic and robust, with some agents providing no benefit. Severe thrombocytopenia is an infrequent, but potentially serious, complication of therapy with all of the agents. The risk of major bleeding is increased only minimally or not at all by the drugs. Currently, a number of new indications for GPIIb/IIIa antagonists are under study, including acute myocardial infarction (+/- thrombolytic therapy, +/- PCI) and stroke. In addition to their impact on improving outcome, the results of clinical trials with these agents provide crucial insights into the contribution of GPIIb/IIIa-mediated platelet function in the pathophysiology of thrombotic vascular disease.

Alteplase and tenecteplase: applications in the peripheral circulation

Alteplase (t-PA), a recombinant analogue of human tissue plasminogen activator, became the first genetically engineered thrombolytic approved by the Food and Drug Administration in 1987 for acute myocardial infarction (AMI). In addition to AMI, alteplase is currently approved for the treatment of acute ischemic stroke and pulmonary embolism, and we anticipate approval for catheter clearance in late 2001 in a 2-mg vial configuration. With the withdrawal of human neonatal kidney cell-derived urokinase, alteplase has become an alternative agent in peripheral vascular applications. Because few interventionalists had prior experience with the handling and dosage of alteplase, the Advisory Panel to the Society of Cardiovascular and Interventional Radiology established practice guidelines for use in noncoronary applications. Emerging clinical experience with contemporary dosing regimens shows a safety and efficacy profile similar to urokinase but with significantly reduced drug costs. Tenecteplase (TNK) is a genetically modified version of alteplase. TNK is the only plasminogen activator available that has shown a significantly enhanced safety profile versus alteplase in AMI. Approved for a 5-second, single-bolus injection in AMI, TNK possesses a longer half-life, increased resistance to plasminogen activator inhibitor, and improved fibrin specificity compared with alteplase. Because of its enhanced safety profile, TNK may be a desirable agent for peripheral vascular applications. Initial clinical studies with TNK in acute arterial and venous disease are ongoing. This article outlines the Advisory Panel guidelines for using alteplase and highlights features of tenecteplase.

Low molecular weight heparin therapy for percutaneous coronary intervention: a practice in evolution

Unfractionated heparin (UFH) remains the principal antithrombotic agent during percutaneous coronary intervention (PCI) but is associated with significant limitations including an unpredictable anticoagulation dose response, the requirement for frequent monitoring, and transient rebound hypercoagulability. Low molecular weight heparin (LMWH) represents an attractive alternative due to its predictable dose response relationship, superior antithrombotic efficacy and potential for improved clinical safety, and has been used increasingly in patients with acute coronary syndromes prior to coronary angiography. The rationale and existing data regarding the use of LMWH in PCI is summarized and reviewed. Preliminary clinical guidelines for the use of LMWH in the transition from medical stabilization of patients with acute coronary syndromes to invasive management in the catheterization laboratory are presented.

Comparative efficacy of low-molecular-weight heparins in orthopedic surgery

The low-molecular-weight heparins (LMWHs) have been evaluated in the prevention of postoperative thromboembolic disease and have been found to be clinically efficacious and safe. Studies conducted in similar surgery settings have resulted in significantly different reductions in the incidence of deep-vein thrombosis, making an analysis of grouped studies complex. Only two studies have reported head-to-head comparisons of two different LMWHs and showed no difference in clinical end points between enoxaparin and either reviparin or tinzaparin. Our study at the Aalborg hospital in Denmark, comparing two different dosage regimens of LMWH tinzaparin, supported the conclusions of the head-to-head comparative studies. LMWHs are distinct drug entities that cannot be interchanged at equivalent anti-Xa dosages, and the interpretation of their relative efficacy and safety may be biased by the degree of clinical experience of the individual investigators.

Antithrombotics and anticoagulants in coronary syndromes and stroke

The low-molecular-weight heparins (LMWHs) have been proven superior to placebo in reducing the incidence of acute coronary ischemic syndromes. Comparative studies vs. unfractionated heparin have not demonstrated superiority in favor of the LMWH dalteparin. In the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events (ESSENCE) trial, enoxaparin was demonstrated to have a benefit over heparin. The results have contributed to a better understanding of the relative efficacy of LMWHs in acute coronary syndromes. A second trial with enoxaparin supported the conclusions of the ESSENCE trial. The antithrombotic effects of LMWHs have also been evaluated for the management of ischemic stroke with varied results. A trial assessing tinzaparin in acute ischemic stroke has completed enrollment, and its results may shed new light on the use of an LMWH for the management of stroke.

An update on heparins at the beginning of the new millennium

Unfractionated heparin has enjoyed the sole anticoagulant status for almost half a century. Besides an effective anticoagulant, this drug has been used in several additional indications. Despite the development of newer anticoagulant drugs, unfractionated heparin has remained the drug of choice for surgical anticoagulation and interventional cardiology. In the area of hematology and transfusion medicine, unfractionated heparin has continued to play a major role as an anticoagulant drug. The development of low-molecular-weight heparins (LMWHs) represents a refinement for the use of heparin. These drugs represent a class of depolymerized heparin derivatives with a distinct pharmacologic profile that is largely determined by their composition. These drugs produce their major effects by combining with antithrombin and exerting antithrombin and anti-Xa inhibition. In addition, the LMWHs also increase non-antithrombin-dependent effects such as TFPI release, modulation of adhesion molecules, and release of profibrinolytic and antithrombotic mediators from the blood vessels. The cumulative effects of each of the different LMWHs differ and each product exhibits a distinct profile. Initially these agents were developed for the prophylaxis of postsurgical deep-vein thrombosis. However, at this time these drugs are used not only for prophylaxis, but also for the treatment of thrombotic disorders of both the venous and arterial type. To a large extent, the LMWHs have replaced unfractionated heparin in most subcutaneous indications. With the use of these refined heparins, outpatient anticoagulant management has gone through a dramatic evolution. For the first time, patients with thrombotic disorders can be treated in an outpatient setting. Thus, the introduction of LMWHs represents a major advance in improving the use of heparin. The development of the oral formulation of heparin and LMWHs also provides an important area that may impact on the use of heparin and LMWHs. The increased awareness of heparin-induced thrombocytopenia has necessitated the development of newer methods to identify patients at risk of developing this catastrophic syndrome. Furthermore, a strong interest has developed in alternate drugs or the management of patients with this syndrome. Despite the development of alternate anticoagulants that are mostly antithrombin derived (hirudins, hirulog), these agents have failed to provide similar clinical outcome as heparin in many indications. However, antithrombin drugs are useful in the anticoagulant management of heparin-compromised patients. The FDA has approved a recombinant hirudin (Refludan) and a synthetic antithrombin agent, argatroban (Novastan), for this indication. The development of synthetic heparin pentasaccharide and anti-Xa agents may have an impact on the prophylaxis of thrombotic disorders. However, these monotherapeutic agents do not mimic the polytherapeutic actions of heparin. Furthermore, these agents do not inhibit thrombin. Heparin and LMWHs are capable of inhibiting not only factor Xa and thrombin, but other serine proteases in the coagulation network. The only way the newer drugs can mimic the actions of heparin is in combination modalities (polytherapeutic approaches). It has been suggested that newer antiplatelet drugs also exhibit anticoagulant actions. While these drugs may exhibit weak effects on thrombin generation, none of the currently available antiplatelet drugs exhibit any degree of antithrombin actions. It is likely that heparins synergize or augment the effects of the new antiplatelet drugs. Currently, combination approaches are used to anticoagulate patients in these studies. The dosage of heparins has been arbitrarily reduced. This may not be an optimal procedure. Additional clinical studies are needed to study these combinations where the alterations of these drugs are compared. Such combinations will require newer monitoring approaches. The development of oral thrombin agents, GP IIb

Development of tinzaparin: a heparinase-digested low-molecular-weight heparin

Although heparin and its properties had been discovered in the early 1920s, the different characteristics associated with different molecular-weight fractions of heparin were only recognized in the late 1970s. Tinzaparin is a low-molecular-weight heparin (LMWH) produced by heparinase digestion of heparin. Preclinical research on tinzaparin established that there were no differences in the antithrombotic activity compared with heparin. Clinical studies evaluating tinzaparin vs. standard heparin for thromboprophylaxis of deep-vein thrombosis in general and orthopedic surgery found that tinzaparin was as effective as standard heparin. Tinzaparin was also evaluated vs. standard heparin in the treatment of acute proximal vein thrombosis; time-to-event curves suggested that this LMWH could be more effective than standard heparin.

The TETAMI trial: the safety and efficacy of subcutaneous enoxaparin versus intravenous unfractionated heparin and of tirofiban versus placebo in the treatment of acute myocardial infarction for patients not thrombolyzed: methods and design

Patients with acute myocardial infarction (AMI) who do not receive early reperfusion therapy are at high risk of reinfarction or death, and the efficacy and safety of antithrombotic therapy in this group of patients has not been evaluated. Enoxaparin is a low-molecular-weight heparin (LMWH) that has previously been shown to reduce the incidence of ischemic events in patients with unstable angina or non-Q-wave MI. The principal aims of the TETAMI study are to investigate the efficacy and safety of treatment with enoxaparin or tirofiban (a glycoprotein IIb/IIIa receptor antagonist) alone or in combination for 2 to 8 days in patients with AMI who are not eligible for early reperfusion therapy. In this 2 by 2 factorial design study approximately 900 patients will be randomly assigned, in a blinded manner, to one of four treatments: enoxaparin alone, enoxaparin plus tirofiban, unfractionated heparin (UFH), or UFH plus tirofiban, with appropriate matched placebos. The primary end point is the composite of death, recurrent AMI, and recurrent angina, analyzed at 30 days after AMI. The design and methods of the TETAMI study are described in this article.

The role of low-molecular-weight heparins in arterial diseases: optimizing antithrombotic therapy

On the basis of current evidence, all patients with acute coronary syndromes should receive optimized medical therapy, whether or not they ultimately undergo an invasive revascularization procedure, to improve both clinical outcomes and cost effectiveness. While standard aspirin and unfractionated heparin (UFH) have improved short-term outcomes, they do not eliminate the risk of recurrent ischemic episodes. The recent introduction of platelet fibrinogen receptor antagonists and low-molecular-weight heparins (LMWHs) has offered an opportunity to develop more aggressive antithrombotic regimens. The LMWHs have been thoroughly evaluated in unstable angina and non-Q wave myocardial infarction (UA/NQMI), and have demonstrated improved efficacy compared to standard UFH, without an increase in major complications caused by bleeding. Experience has also been gathered using LMWHs in other arterial diseases (such as pregnant patients with prosthetic heart valves) and as an adjunctive therapy with thrombolytics for acute myocardial infarction. Lastly, studies are currently underway evaluating LMWHs in patients with atrial fibrillation.

Combination of a direct thrombin inhibitor and a platelet glycoprotein IIb/IIIa blocking peptide facilitates and maintains reperfusion of platelet-rich thrombus with alteplase

We sought to determine the efficacy of the combination of argatroban, a direct thrombin inhibitor, and G4120, a platelet glycoprotein (GP) IIb/IIIa blocker, to enhance thrombolysis with alteplase. Platelet-rich thrombus in the rabbit arterial thrombosis model is relatively resistant to alteplase despite the addition of aspirin and heparin. The adjunctive use of either direct thrombin inhibitors or GP IIb/IIIa inhibitors in thrombolysis has been investigated with encouraging, but limited, success. The usefulness of combining both agents as adjunctive therapy to thrombolysis has not been fully explored. Following platelet-rich thrombus formation in the rabbit, argatroban (3 mg/kg), G4120 (0.5 mg/kg), G4120 plus heparin (200 U/kg), or G4120 plus argatroban were intravenously infused over 60 minutes. Alteplase was given as intravenous boluses (0.45 mg/kg) at 15-minute intervals up to 4 doses or until reperfusion. Blood flow and bleeding time were monitored for 2 hours. The combination of G4120 plus argatroban resulted in a persistent patency in 5 of 7 animals compared with 0 of 6 for argatroban alone (p=0.02), 1 of 6 for G4120 alone (p=0.08), and 2 of 6 for G4120 plus heparin (p=0.2). Although during the infusion the bleeding times were longer in the groups that received G4120 (26+/-7.7 minutes vs. 14+/-10 minutes, p<0.05), by the end of the experiment there were no statistically significant differences. Similarly, during the infusion the activated partial thromboplastin times (aPTT) was higher in groups that received heparin or argatroban (99+/-51 seconds vs. 32+/-7.6 seconds, p<0.001), but by the end of the experiment the aPTTs had returned to close to baseline in all groups except the G4120 plus heparin group. These results suggest that lysis of platelet-rich thrombus with alteplase requires the addition of both potent platelet and thrombin inhibitors. Specifically designed agents, G4120 and argatroban, are effective without additional increased risk for bleeding.

Comparing the antithrombotic efficacy of a humanized anti-factor IX(a) monoclonal antibody (SB 249417) to the low molecular weight heparin enoxaparin in a rat model of arterial thrombosis

A humanized inhibitory anti-factor IX(a) antibody (SB 249417) has been compared to enoxaparin (Lovenox) in a rat model of arterial thrombosis. Pretreatment of rats with either SB 249417 (3.0 mg/kg, i. v.) or enoxaparin (30.0 mg/kg, i.v. or s.c.) resulted in comparable and significant reductions in thrombus formation. However, the efficacious dose of enoxaparin resulted in >30-fold increase in the aPTT over baseline, while the efficacious dose of SB 249417 prolonged the aPTT by only approximately 3-fold. Additionally, pretreatment with SB 249417 resulted in sustained blood flow and arterial patency throughout the experiment in >80% of rats treated. In contrast, <30% of rats pretreated with enoxaparin remained patent throughout the experiment. The data in this report indicate that the selective inhibition of factor IX(a) with the monoclonal antibody SB 249417 produces a superior antithrombotic profile to that of the low molecular weight heparin enoxaparin.

Loco-regional thrombolysis for deep vein thrombosis: fact or fiction? A study of hemostatic parameters

Loco-regional thrombolysis for deep-vein thrombosis (DVT) has been claimed to be equally effective and safe compared with systemic thrombolysis. It is not known whether a loco-regional thrombolytic effect exists and of what it might consist. To investigate this issue, we studied eight patients with DVT undergoing loco-regional thrombolysis with 20 mg alteplase infused over 4 h in a dorsal foot-vein of the affected leg, while the leg was kept tightly bandaged; alteplase infusions were repeated every 24 h, the number of therapy cycles (TC) was seven, and full-dose heparin was given. For coagulation analyses, 'loco-regional' blood samples were taken from a vein of the affected leg and 'systemic' samples were taken from an antecubital vein. After a median number of six TC, good partial reperfusion was achieved in 4/8 patients, moderate partial reperfusion in 2/8, major bleedings occurred in 2/8, and minor bleedings in 1/8 patients. During the first TC, recombinant tissue-type plasminogen activator (rtPA) activity and antigen, as well as FgDPs and d-dimers, were elevated significantly loco-regionally over systemic values, and a complete breakdown of plasmin-inhibitor activity occurred with only a slight systemic reduction; no other differences were found. During successive TC, differences in rtPA-activity and -antigen levels decreased, and no significant differences were found for all other parameters. Thus, a local fibrinolytic effect was demonstrable during loco-regional thrombolysis for DVT; the magnitude of this effect diminished during successive TC, giving rise to the hypothesis that the fibrinolytic efficacy may be decreased due to growing, antifibrinolytic activity. The preserved, loco-regional plasmin-inhibitor activities during the later TC, in contrast to the complete breakdown during the first TC, suggest that part of the enhanced antifibrinolytic activity is due to loco-regionally increased plasmin-inhibitor activity. The ultimate goal of loco-regional thrombolysis, the induction of local fibrinolysis without systemic effects, has not, however, been achieved.

[Streptokinase: correlation between different methods of biological evaluation]

A study was carried out to establish an appropriate method for streptokinase (SK) potency determination (biological assay) in order to fulfil the main function of the Instituto Nacional de Medicamentos respecting products marketed in Argentina. The potency of different commercial samples of SK was determined against the International Standard, and three internationally accepted methods were used for this purpose: fibrin plate, clot lysis and chromogenic method. The analysis of results suggests that the fibrin plate method is the least precise and reproducible. The clot lysis and chromogenic methods demonstrated great precision and reproducibility, giving a correlation coefficient of 0.99. It is concluded that both of these methods are best suited to determine potency of SK commercial products.