Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

This article describes the pharmacology of approved parenteral anticoagulants. These include the indirect anticoagulants, unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs), fondaparinux, and danaparoid, as well as the direct thrombin inhibitors hirudin, bivalirudin, and argatroban. UFH is a heterogeneous mixture of glycosaminoglycans that bind to antithrombin via a unique pentasaccharide sequence and catalyze the inactivation of thrombin, factor Xa, and other clotting enzymes. Heparin also binds to cells and plasma proteins other than antithrombin causing unpredictable pharmacokinetic and pharmacodynamic properties and triggering nonhemorrhagic side effects, such as heparin-induced thrombocytopenia (HIT) and osteoporosis. LMWHs have greater inhibitory activity against factor Xa than thrombin and exhibit less binding to cells and plasma proteins than heparin. Consequently, LMWH preparations have more predictable pharmacokinetic and pharmacodynamic properties, have a longer half-life than heparin, and are associated with a lower risk of nonhemorrhagic side effects. LMWHs can be administered once daily or bid by subcutaneous injection, without coagulation monitoring. Based on their greater convenience, LMWHs have replaced UFH for many clinical indications. Fondaparinux, a synthetic pentasaccharide, catalyzes the inhibition of factor Xa, but not thrombin, in an antithrombin-dependent fashion. Fondaparinux binds only to antithrombin. Therefore, fondaparinux-associated HIT or osteoporosis is unlikely to occur. Fondaparinux exhibits complete bioavailability when administered subcutaneously, has a longer half-life than LMWHs, and is given once daily by subcutaneous injection in fixed doses, without coagulation monitoring. Three additional parenteral direct thrombin inhibitors and danaparoid are approved as alternatives to heparin in patients with HIT.

Heparin plus a glycoprotein IIb/IIIa inhibitor versus bivalirudin monotherapy and paclitaxel-eluting stents versus bare-metal stents in acute myocardial infarction (HORIZONS-AMI): final 3-year results from a multicentre, randomised controlled trial

BACKGROUND

Primary results of the HORIZONS-AMI trial have been previously reported. In this final report, we aimed to assess 3-year outcomes.

METHODS

HORIZONS-AMI was a prospective, open-label, randomised trial undertaken at 123 institutions in 11 countries. Patients aged 18 years or older were eligible for enrolment if they had ST-segment elevation myocardial infarction (STEMI), presented within 12 h after onset of symptoms, and were undergoing primary percutaneous coronary intervention. By use of a computerised interactive voice response system, we randomly allocated patients 1:1 to receive bivalirudin or heparin plus a glycoprotein IIb/IIIa inhibitor (GPI; pharmacological randomisation; stratified by previous and expected drug use and study site) and, if eligible, randomly allocated 3:1 to receive a paclitaxel-eluting stent or a bare metal stent (stent randomisation; stratified by pharmacological group assignment, diabetes mellitus status, lesion length, and study site). We produced Kaplan-Meier estimates of major adverse cardiovascular events at 3 years by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00433966.

FINDINGS

Compared with 1802 patients allocated to receive heparin plus a GPI, 1800 patients allocated to bivalirudin monotherapy had lower rates of all-cause mortality (5·9%vs 7·7%, difference -1·9% [-3·5 to -0·2], HR 0·75 [0·58-0·97]; p=0·03), cardiac mortality (2·9%vs 5·1%, -2·2% [-3·5 to -0·9], 0·56 [0·40-0·80]; p=0·001), reinfarction (6·2%vs 8·2%, -1·9% [-3·7 to -0·2], 0·76 [0·59-0·99]; p=0·04), and major bleeding not related to bypass graft surgery (6·9%vs 10·5%, -3·6% [-5·5 to -1·7], 0·64 [0·51-0·80]; p=0·0001) at 3 years, with no significant differences in ischaemia-driven target vessel revascularisation, stent thrombosis, or composite adverse events. Compared with 749 patients who received a bare-metal stent, 2257 patients who received a paclitaxel-eluting stent had lower rates of ischaemia-driven target lesion revascularisation (9·4%vs 15·1%, -5·7% [-8·6 to -2·7], 0·60 [0·48-0·76]; p<0·0001) after 3 years, with no significant differences in the rates of death, reinfarction, stroke or stent thrombosis. Stent thrombosis was high (≥4·5%) in both groups.

INTERPRETATION

The effectiveness and safety of bivalirudin monotherapy and paclitaxel-eluting stenting are sustained at 3 years for patients with STEMI undergoing primary percutaneous coronary intervention.

FUNDING

Boston Scientific and The Medicines Company.

A comparison of recombinant hirudin with a low-molecular-weight heparin to prevent thromboembolic complications after total hip replacement

BACKGROUND

Patients who undergo total hip replacement have a high risk of thromboembolic complications. Recombinant hirudin (desirudin), a specific inhibitor of thrombin, represents a new development in antithrombotic therapy. We compared the efficacy and safety of desirudin with those of a low-molecular-weight heparin (enoxaparin) for the prevention of thromboembolic complications in patients undergoing primary total hip replacement.

METHODS

Both treatments, which were assigned in a randomized, double-blind manner, were started preoperatively: enoxaparin on the evening before surgery, and desirudin within 30 minutes before the start of surgery. The dose of desirudin was 15 mg subcutaneously twice daily, and the dose of enoxaparin was 40 mg subcutaneously once daily. The duration of treatment was 8 to 12 days. Deep-vein thrombosis was verified by bilateral venography performed at the end of the treatment period or earlier, if there were clinical signs of deep-vein thrombosis.

RESULTS

At 31 centers in 10 European countries, 2079 eligible patients were randomly assigned to receive desirudin or enoxaparin. A total of 1587 patients were included in the primary analysis of efficacy. In the desirudin group, as compared with the enoxaparin group, there was a significantly lower rate of proximal deep-vein thrombosis (4.5 vs. 7.5 percent, P=0.01; relative reduction in risk, 40.3 percent) and a lower overall rate of deep-vein thrombosis (18.4 vs. 25.5 percent, P=0.001; relative reduction in risk, 28.0 percent). The safety profiles were similar in the two treatment groups.

CONCLUSIONS

When administered 30 minutes before total hip replacement surgery, desirudin is more effective than enoxaparin in preventing deep-vein thrombosis.

Heparin-induced thrombocytopenia and cardiac surgery

Unfractionated heparin given during cardiopulmonary bypass is remarkably immunogenic, as 25% to 50% of postcardiac surgery patients develop heparin-dependent antibodies during the next 5 to 10 days. Sometimes, these antibodies strongly activate platelets and coagulation, thereby causing the prothrombotic disorder, heparin-induced thrombocytopenia. The risk of heparin-induced thrombocytopenia is 1% to 3% if unfractionated heparin is continued beyond the first postoperative week. When cardiac surgery is urgently needed for a patient with acute or subacute heparin-induced thrombocytopenia, options include an alternative anticoagulant (bivalirudin, lepirudin, or danaparoid) or combining unfractionated heparin with a platelet antagonist (epoprostenol or tirofiban). As heparin-induced thrombocytopenia antibodies are transient, unfractionated heparin alone is appropriate in a patient with previous heparin-induced thrombocytopenia whose antibodies have disappeared.

Radial versus femoral access and bivalirudin versus unfractionated heparin in invasively managed patients with acute coronary syndrome (MATRIX): final 1-year results of a multicentre, randomised controlled trial

BACKGROUND

The Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of Angiox (MATRIX) programme was designed to assess the comparative safety and effectiveness of radial versus femoral access and of bivalirudin versus unfractionated heparin with optional glycoprotein IIb/IIIa inhibitors in patients with the whole spectrum of acute coronary syndrome undergoing invasive management. Here we describe the prespecified final 1-year outcomes of the entire programme.

METHODS

MATRIX was a programme of three nested, randomised, multicentre, open-label, superiority trials in patients with acute coronary syndrome in 78 hospitals in Italy, the Netherlands, Spain, and Sweden. Patients with ST-elevation myocardial infarction were simultaneously randomly assigned (1:1) before coronary angiography to radial or femoral access and to bivalirudin, with or without post-percutaneous coronary intervention infusion or unfractionated heparin (one-step inclusion). Patients with non-ST-elevation acute coronary syndrome were randomly assigned (1:1) before coronary angiography to radial or femoral access and, only if deemed eligible to percutaneous coronary intervention after angiography (two-step inclusion), entered the antithrombin type and treatment duration programmes. Randomisation sequences were computer generated, blocked, and stratified by intended new or current use of P2Y12 inhibitor (clopidogrel vs ticagrelor or prasugrel), and acute coronary syndrome type (ST-elevation myocardial infarction, troponin-positive, or troponin-negative non-ST-elevation acute coronary syndrome). Bivalirudin was given as a bolus of 0·75 mg/kg, followed immediately by an infusion of 1·75 mg/kg per h until completion of percutaneous coronary intervention. Heparin was given at 70-100 units per kg in patients not receiving glycoprotein IIb/IIIa inhibitors, and at 50-70 units per kg in patients receiving glycoprotein IIb/IIIa inhibitors. Clinical follow-up was done at 30 days and 1 year. Co-primary outcomes for MATRIX access and MATRIX antithrombin type were major adverse cardiovascular events, defined as the composite of all-cause mortality, myocardial infarction, or stroke up to 30 days; and net adverse clinical events, defined as the composite of non-coronary artery bypass graft-related major bleeding, or major adverse cardiovascular events up to 30 days. The primary outcome for MATRIX treatment duration was the composite of urgent target vessel revascularisation, definite stent thrombosis, or net adverse clinical events up to 30 days. Analyses were done according to the intention-to-treat principle. This trial is registered with ClinicalTrials.gov, number NCT01433627.

FINDINGS

Between Oct 11, 2011, and Nov 7, 2014, we randomly assigned 8404 patients to receive radial (4197 patients) or femoral (4207 patients) access. Of these 8404 patients, 7213 were included in the MATRIX antithrombin type study and were randomly assigned to bivalirudin (3610 patients) or heparin (3603 patients). Patients assigned to bivalirudin were included in the MATRIX treatment duration study, and were randomly assigned to post-procedure infusion (1799 patients) or no post-procedure infusion (1811 patients). At 1 year, major adverse cardiovascular events did not differ between patients assigned to radial access compared with those assigned to femoral access (14·2% vs 15·7%; rate ratio 0·89, 95% CI 0·80-1·00; p=0·0526), but net adverse clinical events were fewer with radial than with femoral access (15·2% vs 17·2%; 0·87, 0·78-0·97; p=0·0128). Compared with heparin, bivalirudin was not associated with fewer major adverse cardiovascular (15·8% vs 16·8%; 0·94, 0·83-1·05; p=0·28) or net adverse clinical events (17·0% vs 18·4%; 0·91, 0·81-1·02; p=0·10). The composite of urgent target vessel revascularisation, stent thrombosis, or net adverse clinical events did not differ with or without post-procedure bivalirudin infusion (17·4% vs 17·4%; 0·99, 0·84-1·16; p=0·90).

INTERPRETATION

In patients with acute coronary syndrome, radial access was associated with lower rates of net adverse clinical events compared with femoral access, but not major adverse cardiovascular events at 1 year. Bivalirudin with or without post-procedure infusion was not associated with lower rates of major adverse cardiovascular events or net adverse clinical events. Radial access should become the default approach in acute coronary syndrome patients undergoing invasive management.

FUNDING

Italian Society of Invasive Cardiology, The Medicines Company, Terumo, amd Canada Research Chairs Programme.

Use of a direct antithrombin, hirulog, in place of heparin during coronary angioplasty

BACKGROUND

Since the inception of coronary angioplasty, heparin with or without aspirin has been routinely given intraprocedurally to avoid coronary thrombotic complications. Recently, the direct thrombin inhibitor hirulog has been demonstrated to inactivate clot-bound thrombin. The present study was a multicenter dose escalation of hirulog to determine its appropriate dose and feasibility as the sole anticoagulant during coronary angioplasty.

METHODS AND RESULTS

At 11 participating centers, 291 patients undergoing elective coronary angioplasty and pretreated with 325 mg aspirin daily were enrolled in sequential groups of intravenously administered hirulog instead of heparin as follows: group 1: bolus, 0.15 mg/kg; infusion, 0.6 mg.kg-1.hr-1 (54 patients); group 2: bolus, 0.25 mg/kg; infusion, 1.0 mg.kg-1.hr-1 (53 patients); group 3: bolus, 0.35 mg/kg; infusion, 1.4 mg.kg-1.hr-1 (44 patients); group 4: bolus, 0.45 mg/kg; infusion, 1.8 mg.kg-1.hr-1 (74 patients); and group 5: bolus, 0.55 mg/kg; infusion, 2.2 mg.kg-1.hr-1 (54 patients). The hirulog infusion was maintained for 4 hours; the primary end point was abrupt vessel closure within 24 hours of the initiation of the procedure. Activated clotting times (ACT) and activated partial thromboplastin times (aPTT) were serially monitored. Abrupt vessel closure occurred in 18 patients (6.2%). By intention to treat, the abrupt closure event rate for groups 1-3 was 11.3% compared with 3.9% in groups 4 and 5 (p = 0.052). There were no significant bleeding complications except for one patient in group 1, who received a two-unit transfusion. A dose-response curve of both ACTs and aPTTs was noted; no coronary thrombotic closures occurred in the small number of patients with ACT > 300 seconds.

CONCLUSIONS

The present study documents for the first time that it is possible to perform coronary angioplasty with an anticoagulant other than heparin in aspirin-pretreated patients. Hirulog was associated with a rapid onset, dose-dependent anticoagulant effect, minimal bleeding complications, and at doses of 1.8-2.2 mg/kg, a rate of 3.9% for abrupt vessel closure.

Controlled delivery of recombinant hirudin based on thermo-sensitive Pluronic® F127 hydrogel for subcutaneous administration: In vitro and in vivo characterization

Here we investigated thermo-sensitive Pluronic(R) F127 (PF127) hydrogel for the controlled release of peptide and protein drugs after subcutaneous injection, using an antithrombotic polypeptide, recombinant hirudin variant-2 (rHV2), as the model drug. The in vitro release experiment performed with a membrane-less model at 37 degrees C showed that the release of antithrombotic activity of rHV2 from PF127 gel followed zero-order kinetics and correlated well with the weight percentage of PF127 dissolved, indicating a dissolution-controlled release mechanism. The in vivo result obtained after subcutaneous injection of rHV2-loaded PF127 gel in normal rats demonstrated that PF127 gel improved the bioavailability, prolonged the antithrombotic effect of rHV2, and induced detectable plasma rHV2 concentration for a longer time in comparison with rHV2 aqueous solution. Differential scanning calorimetry, dynamic light scattering and Fourier transform infrared spectroscopy provided evidence of the interaction between PF127 and rHV2, but such interaction was unlikely to interfere the feasibility of this drug delivery system. Our current in vitro and in vivo study suggested that PF127 gel may be useful as an injectable delivery vehicle for peptides and proteins with short half-lives to prolong their therapeutic effect, increase their bioavailability and improve the clinic outcome.

Bivalirudin pharmacokinetics and pharmacodynamics: effect of renal function, dose, and gender

BACKGROUND

These studies were conducted to determine whether bivalirudin clearance and pharmacodynamics are dependent on dose, renal function, or gender.

METHODS

Two studies were performed. The first comprised 25 patients who were undergoing percutaneous coronary intervention-8 with normal renal function, 11 with mild renal impairment, and 6 with moderate renal impairment. Each patient received a bolus dose of bivalirudin (1 mg/kg) followed by an infusion (2.5 mg/kg per hour for 4 of 6 hours, then 0.5 mg/kg per hour for 4 of 6 hours). The second study enrolled 8 volunteers with severe renal impairment who received a bivalirudin bolus of 1 mg/kg, followed by an infusion of 0.5 mg/kg per hour for 10 hours. Bivalirudin in plasma and urine was assayed with a newly developed, highly specific liquid chromatography-mass spectrometry assay.

RESULTS

Clearances at the two infusion doses did not differ significantly (3.23 mL/min per kilogram and 3.16 mL/min per kilogram). There was no statistically significant difference in area under the concentration-time curve (AUC) and in plasma clearance between patients with normal renal function and those with mild renal impairment. Patients with moderate and severe renal impairment had reductions in plasma clearance of 21% and 24%, respectively. The level of anticoagulation(activated clotting time) was similar between groups. There was no difference between male and female patients.

CONCLUSION

The clearance of bivalirudin is dependent on renal function but independent of dose and gender. Approximately 20% of unchanged drug is cleared via the kidney, and the remainder presumably undergoes proteolysis intracellularly. The pharmacodynamics of bivalirudin are dose-dependent and gender-independent. Bivalirudin kinetics are linear in the dose ranges that are used in percutaneous coronary intervention and that are under investigation for use in acute coronary syndromes.

Relationship Between Activated Clotting Time and Ischemic or Hemorrhagic Complications

Background— Unfractionated heparin (UFH) is the most widely used antithrombin during percutaneous coronary intervention (PCI). Despite significant pharmacological and mechanical advancements in PCI, uncertainty remains about the optimal activated clotting time (ACT) for prevention of ischemic or hemorrhagic complications.

Methods and Results— We analyzed the outcome of all UFH-treated patients enrolled in 4 large, contemporary PCI trials with independent adjudication of ischemic and bleeding events. Of 9974 eligible patients, maximum ACT was available in 8369 (84%). The median ACT was 297 seconds (interquartile range 256 to 348 seconds). The incidence of death, myocardial infarction, or revascularization at 48 hours, by ACT quartile, was 6.2%, 6.8%, 6.0%, and 5.7%, respectively ( P =0.40 for trend). Covariate-adjusted rate of ischemic complications was not correlated with maximal procedural ACT (continuous value, P =0.29). Higher doses of UFH (>5000 U, or up to 90 U/kg) were independently associated with higher rates of events. The incidence of major or minor bleeding at 48 hours, by ACT quartile, was 2.9%, 3.5%, 3.8%, and 4.0%, respectively ( P =0.04 for trend). In a multivariable logistic model with a spline transformation for ACT, there was a linear increase in risk of bleeding as the ACT approached 365 seconds ( P =0.01), which leveled off beyond that value. Increasing UFH weight-indexed dose was independently associated with higher bleeding rates (OR 1.04 [1.02 to 1.07] for each 10 U/kg, P =0.001).

Conclusions— In patients undergoing PCI with frequent stent and potent platelet inhibition use, ACT does not correlate with ischemic complications and has a modest association with bleeding complications, driven mainly by minor bleeding. Lower values do not appear to compromise efficacy while increasing safety.

Effect of age on outcome with primary angioplasty versus thrombolysis

OBJECTIVES

The purpose of this study was to determine how risks associated with increasing age differed in patients treated with percutaneous transluminal coronary angioplasty versus thrombolysis.

BACKGROUND

Advancing age is a risk factor for adverse outcome in patients with acute myocardial infarction. Primary angioplasty has been thought to be particularly beneficial in higher risk patients including the elderly. There is, however, limited data on any differential incremental benefit of angioplasty compared with thrombolysis in candidates for either treatment.

METHODS

In the GUSTO-IIb angioplasty substudy, 1,138 patients were randomized to receive primary angioplasty or accelerated tissue-type plasminogen activator (t-PA). The effect of age on outcome was assessed as a discrete and continuous variable for each treatment group. Models using age as a linear factor as well as cubic spline transformations were used for the major end points of 30-day death or disabling stroke; death or reinfarction; and death, reinfarction or disabling stroke.

RESULTS

For each 10-year patient group, outcome was improved with angioplasty (n = 565) compared with t-PA (n = 573). Irrespective of treatment, however, risk increased with age. After adjusting for baseline characteristics, each increment of 10 years of age increased the risk of death or myocardial infarction by 1.32 (95% confidence interval 1.04 to 1.76, p = 0.022). For all adverse outcomes, this incremental effect of increasing age was constant.

CONCLUSIONS

Advancing age is associated with worse outcomes, and the risks increase in proportion to age. Although primary angioplasty improves outcomes over thrombolysis, it does not appear to be more beneficial in older than in younger patient groups. The incremental adverse effect of age does not vary by treatment strategy.

Comparison of the effects of two doses of recombinant hirudin compared with heparin in patients with acute myocardial ischemia without ST elevation: a pilot study. Organization to Assess Strategies for Ischemic Syndromes (OASIS) Investigators

BACKGROUND

Despite the use of aspirin and heparin, patients with acute ischemic syndromes are at risk of myocardial infarction (MI) or refractory ischemia. Therefore, evaluation of more potent antithrombotic therapies is warranted.

METHODS AND RESULTS

Patients (n=909) with unstable angina or suspected acute MI without ST-segment elevation were randomized to receive heparin (5000 IU bolus+1000 to 1200 U/h, n=371), low-dose hirudin (LDHir) (0.2 mg/kg bolus+0.10 mg x kg(-1) x h(-1) infusion, n=271), or medium-dose hirudin (MDHir) (0.4 mg/kg bolus+0.15 mg x kg(-1) x h(-1) infusion, n=267) for 72 hours. At 7 days, 6.5% of patients in the heparin group, 4.4% in the LDHir group, and 3.0% in the MDHir group (P=.267 heparin versus low-dose hirudin; P=.047 heparin versus medium-dose hirudin) suffered cardiovascular death, new MI, or refractory angina (primary outcome). The proportions with cardiovascular death, new MI, or refractory or severe angina (secondary outcome) were 15.6%, 12.5%, and 9.4%, respectively (P=.27 for heparin versus LDHir; P=.02 for heparin versus MDHir). The rates of new MI were 4.9%, 2.6%, and 1.9%, respectively (P=.14 heparin versus LDHir; P=.046 heparin versus MDHir). Fewer patients underwent coronary artery bypass graft surgery in the two hirudin groups (3.7% low-dose, 1.1% medium-dose group) compared with heparin (4.0%) (P=.028 for heparin versus MDHir). After cessation of study treatments, there was an increase in ischemic events in the LDHir group at approximately 24 hours and at approximately 5 days in the medium-dose group. Nevertheless, at 180 days, the differences between hirudin and heparin persisted.

CONCLUSIONS

Hirudin, especially at the medium dose, appears to be superior to heparin in preventing ischemic outcomes in unstable angina or acute MI without ST elevation.

Recombinant hirudin for unstable angina pectoris. A multicenter, randomized angiographic trial

BACKGROUND

Coronary artery thrombosis plays an important pathophysiological role in unstable angina and non-Q-wave myocardial infarction. To date, heparin and thrombolytic therapy has not provided complete or consistent benefit. We hypothesized that recombinant hirudin, a direct thrombin inhibitor, would prevent accumulation of coronary artery thrombus in a manner superior to heparin.

METHODS AND RESULTS

Patients with rest ischemic pain, abnormal ECG, and baseline angiogram indicating a > or = 60% stenosis of a culprit coronary artery or saphenous vein graft with visual appearance of thrombus were randomized to one of two different doses of heparin (either a target activated partial thromboplastin time [aPTT] of 65 to 90 or 90 to 110 seconds) or one of four doses of hirudin (0.05, 0.10, 0.20, or 0.30 mg.kg-1.h-1 infusion) in a dose-escalating protocol. After 72 to 120 hours of study drug, a repeat coronary angiogram was obtained, and the paired studies underwent quantitative analysis. The primary end point was change in the average cross-sectional area of the culprit lesion. Other efficacy end points also involved changes in culprit lesion dimensions and TIMI flow grade. Recombinant hirudin led to a dose-dependent elevation of aPTT that appeared to plateau at the 0.2-mg/kg dose. A higher proportion of hirudin-treated patients had their aPTT within a 40-second range (16% heparin versus 71% hirudin, P < .001). Overall, the 116 patients treated with hirudin tended to show more improvement than the 50 patients receiving heparin relative to the primary efficacy variable--the average cross-sectional area (P = .08)--as well as minimal cross-sectional area (P = .028), minimal luminal diameter (P = .029), and percent diameter stenosis (P = .07).

CONCLUSIONS

Recombinant hirudin appears to be a promising antithrombotic intervention compared with heparin for inhibition of coronary artery thrombus. Large-scale comparative trials are warranted.

Influence of diabetes mellitus on clinical outcomes across the spectrum of acute coronary syndromes. Findings from the GUSTO-IIb study. GUSTO IIb Investigators

AIMS

We examined the characteristics, outcomes, and effects of hirudin vs heparin treatment of diabetic patients across the spectrum of acute coronary syndromes.

METHODS AND RESULTS

We studied the 12,142 patients enrolled in the randomized GUSTO-IIb study. Diabetic patients (n=2175) were older, more often female, more often had prior cardiovascular disease, hypertension, and hyperlipidaemia, and less often were current smokers. Diabetic patients had a higher overall incidence of death or (re)infarction at 30 days (13.1% vs 8.5%, P=0.0001), whether they presented with ST-segment elevation (13.9% vs 9.9%, P=0.0017) or not (12.8% vs 7.8%, P=0.0001), and at 6 months (18.8% vs 11.4%, P=0.0001). Among diabetic patients, hirudin was associated with a tendency toward a lower risk of death or (re)infarction at 30 days (12.2% vs 13.9% with heparin) and 6 months (17.8% vs 20.2%). Diabetic patients had more major bleeding, stroke, heart failure, shock, atrioventricular block, and atrial arrhythmias, but no increased risk for ocular bleeding.

CONCLUSIONS

Diabetic patients with acute coronary syndromes had worse 30-day and 6-month outcomes, particularly those without ST-segment elevation. The statistically non-significant trend toward improved outcomes with hirudin was similar among patients with and without diabetes, with a greater point estimate for the absolute difference in patients with diabetes.

Bioactive immobilization of r-hirudin on CVD-coated metallic implant devices

The poor biocompatibility of metallic coronary stents which leads to un-satisfying restenosis rates is mainly caused by contact activation of blood cells, smooth muscle cells and endothelial cells. Mimicking a metal surface with a biocompatible coating that actively suppresses mechanisms leading to restenosis may overcome today's limitations regarding the complications of metal stents. Nitinol coronary stents were coated by CVD polymerization of functionalized [2.2]paracyclophanes. The monomers 4-amino [2.2]paracyclophane, 4-hydroxy methyl [2.2]paracyclophane and [2.2]paracyclophane-4,5,12,13-tetracarboxylic acid dianhydride were previously synthesized. A suitable installation for the CVD polymerization procedure was designed and used for the polymerization procedures. Physical and chemical properties of the polymers were shown to fulfill the requirements regarding the application as a stent coating material. The functional groups of the polymer coatings were used for the immobilization of the thrombin inhibitor r-hirudin. In vitro results indicate that the bioactively coated stents are less thrombogenic than virgin metallic stents. Surface-bound r-hirudin decreases platelet adhesion drastically due to interactions between platelets and r-hirudin.

Prevention of deep-vein thrombosis after total hip replacement: direct thrombin inhibition with recombinant hirudin, CGP 39393

BACKGROUND

The frequency of thromboembolism after major orthopaedic surgery continues to be high despite prophylaxis. New agents such as CGP 39393, a recombinant form of hirudin, may be more effective than existing therapies.

METHODS

In this double-blind, multicentre, European study the efficacy of three doses of CGP 39393, in comparison with unfractionated heparin, were examined in 1119 patients undergoing elective hip surgery. Patients were randomly allocated to receive by subcutaneous injection either 10, 15, or 20 mg of CGP 39393 twice daily or 5000 IU of heparin three times daily. All treatments were started just before surgery and continued for 8-11 days, until bilateral venography was performed.

FINDINGS

The occurrence of thromboembolism was significantly reduced in patients treated with CGP 39393 compared to heparin. The frequency of deep-vein thrombosis was 34.2% in the heparin group as compared to 23.9% (p=0.0113), 18.4% (p=0.0003), and 17.7% (p=0.0001) in the 10 mg, 15 mg, and 20 mg CGP 39393 groups, respectively. At all dose levels, CGP 39393 was more effective than heparin in preventing proximal deep-vein thrombosis. The frequency of proximal thrombosis was 19.6% in the heparin group as compared to 8.5% (p<0.001), 3.1% (p<0.001), and 2.4% (p<0.001) in the 10 mg, 15 mg, and 20 mg CGP 39393 groups, respectively. All treatments were well tolerated.

INTERPRETATION

This study indicates that specific inhibition of thrombin by prophylactic CGP 39393 significantly reduces thromboembolic complications in patients undergoing total hip replacement.

Lepirudin for prophylaxis of thrombosis in patients with acute isolated heparin-induced thrombocytopenia: an analysis of 3 prospective studies

This analysis of 3 prospective multicenter trials in patients with laboratory-confirmed acute heparin-induced thrombocytopenia (HIT) without clinically evident thromboembolic complications (TECs), isolated HIT, assessed the combined individual end points of death, new TECs, and limb amputation. Patients with the same inclusion criteria who did not receive lepirudin or danaparoid served as a contemporaneous control group. Ninety-one patients were treated with lepirudin (intravenous infusion 0.10 mg/kg/h, no bolus, activated partial thromboplastin time [aPTT]-adjusted to 1.5-2.5 times baseline) for a median of 11.0 days (range, 1-68 days). During the observation period (median 24 days), 13 (14.3%) deaths, 4 (4.4%) new TECs, 3 (3.3%) limb amputations (combined 18 [19.8%]), and 13 (14.3%) major bleeding events occurred. In comparison to the control group (N = 47), the combined end point (P = .0281) and new TECs (P = .02) were reduced, and major bleeding was not significantly different between groups (P = .5419). In renal impairment, lepirudin did not reach its steady state within 4 hours, and additional monitoring every 4 hours after start of lepirudin until steady state is reached is recommended. Lepirudin seems to be effective in patients with isolated HIT. Dose reductions in renal impairment are important. Keeping the aPTT in the range corresponding to 600 to 700 microg/L lepirudin during treatment may minimize bleeding complications.

The Ecarin Clotting Time, a Universal Method to Quantify Direct Thrombin Inhibitors

The ecarin clotting time (ECT) is a meizothrombin generation test that allows for precise quantification of direct thrombin inhibitors. The ECT has demonstrated its usefulness for more than 10 years in biochemical-pharmacological investigations as well as in clinical research and in the clinical routine. It has proved valuable especially as a drug-monitoring method in r-hirudin therapy. This test has been adjusted to clinical requirements by numerous modifications. Following the description of the biochemical background and the measuring principle of the ECT, this article gives a short survey of several modifications of the ECT for both preclinical and clinical use, e.g., for biochemical investigations, as a point-of-care method and for cardiac surgery. Advantages and disadvantages of these methods are discussed.

Recombinant hirudin in clinical practice: focus on lepirudin

Clinical applications for recombinant hirudins have been investigated for the past 10 years. The first indication for which a hirudin-lepirudin-has been approved is treatment of heparin-induced thrombocytopenia (HIT). Also, the recently completed trials for use of lepirudin in unstable angina indicate a potentially new indication. This review describes pharmacology and clinical applications of lepirudin with an emphasis on HIT and unstable angina. An overview of usage of lepirudin in acute coronary syndromes is given, as well as a summary of rare indications for lepirudin, such as extracorporeal circulation, for which comprehensive data are lacking.

Fatal cardiac rupture among patients treated with thrombolytic agents and adjunctive thrombin antagonists: observations from the Thrombolysis and Thrombin Inhibition in Myocardial Infarction 9 Study

OBJECTIVES

The purpose of this study was to determine the incidence and demographic characteristics of patients experiencing cardiac rupture after thrombolytic and adjunctive anticoagulant therapy and to identify possible associations between the mechanism of thrombin inhibition (indirect, direct) and the intensity of systemic anticoagulation with its occurrence. BACKGROUND Cardiac rupture is responsible for nearly 15% of all in-hospital deaths among patients with myocardial infarction (MI) given thrombolytic agents. Little is known about specific patient- and treatment-related risk factors. METHODS Patients (n = 3,759) with MI participating in the Thrombolysis and Thrombin Inhibition in Myocardial Infarction 9A and B trials received intravenous thrombolytic therapy, aspirin and either heparin (5,000 U bolus, 1,000 to 1,300 U/h infusion) or hirudin (0.1 to 0.6 mg/kg bolus, 0.1 to 0.2 mg/kg/h infusion) for at least 96 h. A diagnosis of cardiac rupture was made clinically in patients with sudden electromechanical dissociation in the absence of preceding congestive heart failure, slowly progressive hemodynamic compromise or malignant ventricular arrhythmias. RESULTS A total of 65 rupture events (1.7%) were reported-all were fatal, and a majority occurred within 48 h of treatment Patients with cardiac rupture were older, of lower body weight and stature and more likely to be female than those without rupture (all p < 0.001). By multivariable analysis, age >70 years (odds ratio [OR] 3.77; 95% confidence interval [CI] 2.06, 6.91), female gender (OR 2.87; 95% CI 1.44, 5.73) and prior angina (OR 1.82; 95% CI 1.05, 3.16) were independently associated with cardiac rupture. Independent predictors of nonrupture death included age >70 years (OR 3.68; 95% CI 2.53, 5.35) and prior MI (OR 2.14; 95%, CI 1.45, 3.17). There was no association between the type of thrombin inhibition, the intensity of anticoagulation and cardiac rapture. CONCLUSIONS Cardiac rupture following thrombolytic therapy tends to occur in older patients and may explain the disproportionately high mortality rate among women in prior dinical trials. Unlike major hemorrhagic complications, there is no evidence that the intensity of anticoagulation associated with heparin or hirudin administration influences the occurrence of rupture.

Bivalirudin versus heparin and protamine in off-pump coronary artery bypass surgery

BACKGROUND

Bivalirudin is a short-acting direct thrombin inhibitor, with advantages over unfractionated heparin for anticoagulation in cardiac surgery. We hypothesized that bivalirudin is not associated with a clinically important increase in blood loss compared with heparin with protamine reversal in patients undergoing off pump coronary artery bypass (OPCAB) surgery. We also assessed flow with angiography at 3 months using a modified Thombolysis in Myocardial Infarction (TIMI) grade in the grafted coronary arteries.

METHODS

One hundred patients were randomly assigned to receive bivalirudin (0.75 mg/kg bolus, 1.75 mg/kg/h infusion) or heparin (150 to 300 U/kg bolus) with protamine reversal.

RESULTS

A median of 3 (range, 1 to 5) grafts were inserted per patient. Blood loss for the 12 hours after study drug initiation in the bivalirudin group (median, 793 mL; interquartile range, 532 to 1,214 mL; range, 320 to 4,909 mL; n = 50) was not significantly greater than in the heparin group (median, 805 mL; interquartile range, 517 to 1,117 mL; range, 201 to 2,567 mL; n = 50; p = 0.165). Median graft flow was 3.0 in the bivalirudin group (n = 40) and 2.67 in the heparin group (n = 39; p = 0.047). The bivalirudin group had more patients with grade 3 (ie, full) flow in at least 1 graft (100% versus 90%; p = 0.04), a trend toward more patients with grade 3 flow in all grafts (60% versus 38%; p = 0.06), and more grafts with grade 3 flow (82% versus 67%; p = 0.03).

CONCLUSIONS

Anticoagulation for OPCAB surgery with bivalirudin was feasible without a clinically important increase in perioperative blood loss. Graft flow was better in the bivalirudin patients; the impact of this on clinical outcomes requires a larger study.

Monitoring of recombinant hirudin: assessment of a plasma-based ecarin clotting time assay

Assay conditions of a plasma-based ecarin clotting time (ECT) were evaluated and the precision of the ECT in monitoring plasma levels of r-hirudin assessed. The snake venom enzyme ecarin converts prothrombin to meizothrombin possessing only weak coagulant but strong esterase activity. In r-hirudin containing plasma samples, meizo thrombin is rapidly neutralized by r-hirudin resulting in a dose-dependent prolongation of the clotting times. Among the different assay conditions tested, addition of 50 microliters of ecarin (4 U/ml) to 100 microliters of undiluted citrate-anticoagulated plasma gave optimal results with respect to precision and reproducibility. The measuring range of the ECT performed in this way is about 0.02-5.0 micrograms/ml r-hirudin. In vitro studies performed on r-hirudin-spiked plasma samples of 50 healthy individuals demonstrate remarkably low interindividual differences in r-hirudin responsiveness as indicated by CV-values below 5% and 7% at r-hirudin concentrations between 0-3 micrograms/ml and 4-5 micrograms/ml, respectively. The specificity for r-hirudin of the ECT is further demonstrated by the strong correlation (r = 0.94) between the results of a chromogenic assay and the ECT-measured r-hirudin concentrations obtained on 67 ex vivo blood samples. Depending on the concentration of r-hirudin the ECT is sensitive to plasma levels of prothrombin. In the absence of r-hirudin the critical prothrombin concentration was found to be 20% but increasing to 60% in the presence of 2.0 micrograms/ml r-hirudin. A fibrinogen concentration of 50 mg/dl was found to be the minimal concentration independent of the r-hirudin concentration. The precision of the ECT in measuring plasma levels of r-hirudin is not influenced by treatment with heparin, aprotinin or oral anticoagulants. The data demonstrate that the ECT is a rapid and easily perfor mable clotting assay which allows accurate measurement of r-hirudin plasma levels. ECT-monitored hirudin treatment will help to establish optimal dose regimens that are more efficacious but still as safe as heparin.

In Vivo Targeting and Imaging of Atherosclerosis Using Multifunctional Virus-Like Particles of Simian Virus 40

Atherosclerosis is a leading cause of death globally. Targeted imaging and therapeutics are desirable for the detection and treatment of the disease. In this study, we developed trifunctional Simian virus 40 (SV40)-based nanoparticles for in vivo targeting and imaging of atherosclerotic plaques. These novel trifunctional SV40-based nanoparticles encapsulate near-infrared quantum dots and bear a targeting element and a drug component. Using trifunctional SV40-based nanoparticles, we were able to noninvasively fluorescently image atherosclerotic plaques in live intact ApoE(-/-) mice. Near-infrared quantum dots encapsulated in the SV40 virus-like particles showed prominent optical properties for in vivo imaging. When different targeting peptides for vascular cell adhesion molecule-1, macrophages, and fibrin were used, early, developmental, and late stages of atherosclerosis could be targeted and imaged in live intact ApoE(-/-) mice, respectively. Targeted SV40 virus-like particles also delivered an increased concentration of the anticoagulant drug Hirulog to atherosclerosis plaques. Our study provides novel SV40-based nanoparticles with multivalency and multifunctionality suitable for in vivo imaging, molecular targeting, and drug delivery in atherosclerosis.

Heparin-induced thrombocytopenia and cardiac surgery

Unfractionated heparin given during cardiopulmonary bypass is remarkably immunogenic, as 25% to 50% of postcardiac surgery patients develop heparin-dependent antibodies during the next 5 to 10 days. Sometimes, these antibodies strongly activate platelets and coagulation, thereby causing the prothrombotic disorder, heparin-induced thrombocytopenia. The risk of heparin-induced thrombocytopenia is 1% to 3% if unfractionated heparin is continued throughout the postoperative period. When cardiac surgery is urgently needed for a patient with acute or subacute heparin-induced thrombocytopenia, options include an alternative anticoagulant (bivalirudin, lepirudin, or danaparoid) or combining unfractionated heparin with a platelet antagonist (epoprostenol or tirofiban). As heparin-induced thrombocytopenia antibodies are transient, unfractionated heparin alone is appropriate in a patient with previous heparin-induced thrombocytopenia whose antibodies have disappeared.

Randomized comparison of direct thrombin inhibition versus heparin in conjunction with fibrinolytic therapy for acute myocardial infarction: results from the GUSTO-IIb Trial. Global Use of Strategies to Open Occluded Coronary Arteries in Acute Coronary Syndromes (GUSTO-IIb) Investigators

OBJECTIVES

We sought to show that hirudin might interact differently with streptokinase (SK) and tissue-type plasminogen activator (t-PA), which could reduce the incidence of death or reinfarction at 30 days.

BACKGROUND

In a large-scale trial of patients with acute coronary syndromes, hirudin provided modest benefit compared with heparin. However, the interaction with thrombolytic agents was not specifically assessed.

METHODS

Patients with symptoms of acute myocardial infarction and electrocardiographic ST segment elevation were treated with thrombolytic therapy and randomly assigned to receive hirudin or heparin.

RESULTS

A total of 2,274 patients received t-PA, and 1,015 received SK. Baseline characteristics were balanced by antithrombin assignment. Among SK-treated patients, death or reinfarction at 30 days occurred more often in those treated with adjunctive heparin (14.4%) rather than hirudin (8.6%, odds ratio [OR] 1.78, 95% confidence interval [CI] 1.20 to 2.66, p = 0.004). Among t-PA-treated patients, the rates were 10.9% with heparin and 10.3% with hirudin (OR 1.06, 95% CI 0.81 to 1.38, p = 0.68; for treatment heterogeneity: chi-square 4.20, degrees of freedom [df] 1, p = 0.04). After adjustment for baseline differences between thrombolytic groups, the rates were 9.1% for SK with hirudin, 10.3% for t-PA with hirudin, 10.5% for t-PA with heparin and 14.9% for SK with heparin (for treatment heterogeneity: chi-square 4.5, df 1, p = 0.03), suggesting that the beneficial treatment effect of hirudin was limited to the SK-treated patients.

CONCLUSIONS

Hirudin interacts favorably with SK but not t-PA, highlighting the importance of thrombin activity after SK therapy and the potential for simulating the effects of a more potent fibrinolytic agent through direct antithrombin therapy.

Randomized double-blind comparison of two doses of Hirulog with heparin as adjunctive therapy to streptokinase to promote early patency of the infarct-related artery in acute myocardial infarction

BACKGROUND

An improved survival rate is a consequence of successful reperfusion of the infarct-related artery. This double-blind, randomized trial investigated the potential of Hirulog, a direct thrombin inhibitor, to improve the early patency rates obtained with streptokinase and aspirin.

METHODS AND RESULTS

Angiographic patency of the culprit coronary artery lesion was assessed 90 and 120 minutes after the initiation of streptokinase and aspirin and again after 4 +/- 2 days in 68 patients with acute myocardial infarction. Patients were randomized to Hirulog 0.5 mg/kg per hour for 12 hours followed by 0.1 mg/kg per hour (low dose), Hirulog 1.0 mg/kg per hour for 12 hours followed by placebo (high dose), or to heparin 5000 U bolus followed by 1000 U/h titrated to an activated partial thromboplastin time (aPTT) 2 to 2.5 times control after 12 hours. At 90 minutes, TIMI flow grade 2 or 3 was observed in 96% of patients treated with the low dose of Hirulog, in 79% with the high dose, and in 46% with heparin (P = .006) and TIMI flow grade 3 was observed in 85%, 61%, and 31% of patients, respectively (P = .008). At 120 minutes, these figures were 100%, 82%, and 62% for TIMI flow grades 2 and 3 (P = .046) and 92%, 68%, and 46% for TIMI flow grade 3 (P = .014). At 90 minutes, the relative risk for restoring TIMI flow grade 3 was 2.77 with Hirulog 0.5 mg/kg per hour compared with heparin (95% confidence limits, 1.21 to 6.35; P < .001) and 1.4 compared with Hirulog 1.0 mg/kg per minute (95% confidence limits, 1.00 to 1.51; P = .04). Patients who received a placebo infusion after 12 hours experienced more clinical events and reocclusion during the following 4 days than patients in the other two groups.

CONCLUSION

Hirulog yields higher early patency rates in the culprit coronary artery than heparin when used as adjunctive therapy to streptokinase and aspirin in the early phase of acute myocardial infarction. High doses are not required and may be less effective than lower doses, which suggests that too much thrombin inhibition may be harmful.