BACKGROUND

Venous thromboembolism (VTE) is the most frequent complication following craniotomy for brain tumors. At Brigham and Women's Hospital, VTE after craniotomy for brain tumor is the leading cause of deep vein thrombosis (DVT) and pulmonary embolism (PE) among patients hospitalized for conditions other than VTE.

OBJECTIVE

To minimize VTE among patients undergoing craniotomy for brain tumor.

METHODS

Randomized, prospective, double-blind clinical trial.

METHODS

Brigham and Women's Hospital.

METHODS

One hundred fifty patients undergoing craniotomy for brain tumor randomized to enoxaparin, 40 mg/d, vs heparin, 5,000 U bid, with all patients receiving graduated compression stockings and intermittent pneumatic compression.

METHODS

The rate of DVT detected by venous ultrasonography prior to hospital discharge.

RESULTS

Symptomatic DVT or PE developed in none of the patients. The overall rate of asymptomatic VTE was 9.3%, with no significant difference in the rates between the two prophylaxis groups. Ten of the 14 patients identified with VTE had thrombus limited to the deep veins of the calf.

CONCLUSIONS

Enoxaparin, 40 mg/d, or unfractionated heparin, 5,000 U bid, in combination with graduated compression stockings, intermittent pneumatic compression, and predischarge surveillance venous ultrasonography of the legs, resulted in 150 consecutive patients without symptomatic VTE. The low 9.3% frequency of asymptomatic VTE comprised mostly isolated calf DVT. Therefore, this comprehensive, multimodality approach to VTE prophylaxis achieved excellent efficacy and safety.

BACKGROUND

The pathogenesis of unstable angina and non-Q-wave myocardial infarction is still poorly understood, and early evaluation of prognosis remains difficult. We therefore studied the predictive value of 5 biological indicators of inflammation, thrombogenesis, vasoconstriction, and myocardial necrosis, and we examined the effects of enoxaparin and unfractionated heparin on these markers after 48 hours of treatment.

RESULTS

Sixty-eight patients with unstable angina or non-Q-wave myocardial infarction randomized in the international ESSENCE trial participated in this French substudy. C-reactive protein, fibrinogen, von Willebrand factor antigen, endothelin-1 and troponin I were measured on admission and 48 hours later. The composite end point of death, myocardial infarction, recurrent angina, or revascularization was significantly lower at 14 and 30 days of follow-up in patients allocated to enoxaparin compared with unfractionated heparin. All acute-phase reactant proteins were elevated on admission and increased further at 48 hours. Multivariate analysis demonstrated that the rise of von Willebrand factor over 48 hours was a significant and independent predictor of the composite end point at both 14 days and 30 days. Moreover the early increase of von Willebrand factor was more frequent and more severe with unfractionated heparin than with enoxaparin (mean change was +8.7+/-8.8% with enoxaparin versus +93.9+/-11.7% with unfractionated heparin, P<0.0001). The other clinical and biological variables did not predict outcome.

CONCLUSIONS

In patients with unstable angina or non-Q-wave myocardial infarction, the acute-phase proteins increase over the first 2 days despite medical treatment. The early rise of von Willebrand factor is an independent predictor of adverse clinical outcome at 14 days and at 30 days. Enoxaparin provides protection as evidenced by the reduced release of von Willebrand factor, which represents a favorable prognostic finding.

BACKGROUND

The Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial demonstrated that bivalirudin monotherapy significantly reduces major bleeding compared with heparin (unfractionated or enoxaparin) or bivalirudin plus a glycoprotein IIb/IIIa inhibitor in acute coronary syndromes. Whether vascular closure devices (VCD) impact these results is unknown. Therefore, this study sought to determine whether VCD impact major access site bleeding (ASB) in patients with acute coronary syndromes undergoing early invasive management by the femoral approach.

RESULTS

Major ASB in ACUITY was defined as ASB requiring interventional or surgical correction, hematoma>> or =5 cm at the access site, retroperitoneal bleeding, or hemoglobin drop>> or =3 g/dL with ecchymosis or hematoma <5 cm, oozing blood, or prolonged bleeding (>30 minutes) at the access site. Stepwise logistical regression was performed to identify the independent determinants of ASB. Of 11 621 patients undergoing angiography with or without percutaneous coronary intervention by the femoral approach, 4307 (37.1%) received a VCD and 7314 (62.9%) did not. Rates of major ASB were lower with VCD compared with no VCD (2.5% versus 3.3%, relative risk, 0.76; 95% CI, 0.61 to 0.94; P=0.01) and were lowest in patients treated with bivalirudin monotherapy and a VCD (0.7%). Stepwise logistic regression revealed that a VCD (odds ratio, 0.78; 95% CI, 0.61 to 0.99; P=0.04) and bivalirudin monotherapy (odds ratio, 0.35; 95% CI, 0.25 to 0.49; P<0.0001) were both independent determinates of freedom from major ASB.

CONCLUSIONS

In patients with acute coronary syndromes undergoing an early invasive management strategy by the femoral approach, the use of a VCD, bivalirudin monotherapy, or both minimizes rates of major ASB. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00093158.

A variety of pharmaceutical preparations of low-molecular-weight heparins (LMWHs) are available. They belong to the same family of compounds-ie, heparin derivatives with a narrow distribution of mean molecular weights (MWs). LMWHs have different methods of preparation, which result in variations in mean MW, distribution of MW, and pharmacokinetic (PK) and pharmacodynamic (PD) profiles. The mean MW of these compounds ranges from 3,600 to 6,500 daltons. The ratio of anti-Xa (aXa) and anti-IIa (aIIa) activities of the different LMWHs ranges from 1.5 to >10. After subcutaneous (SC) injection of a prophylactic or therapeutic dose, the peak values for plasma aXa or aIIa activity may vary twofold to threefold because of differences in bioavailability, plasma clearance (Clplasma), and half-life (t1/2). The injection of equivalent amounts of product, based on aXa and aIIa international units (IU), may result in different areas under the curve for the respective activities. Although tinzaparin has a high aIIa specific activity per milligram (and consequently, a low aXa/aIIa ratio), SC injection of 40 mg of enoxaparin (4,000 aXa IU) results in a higher aXa peak value in patients with total hip replacement than 4,500 aXa IU of tinzaparin. Differences in aIIa and aXa peak activities are more striking when high doses of LMWHs are used. The activated partial thromboplastin time (aPTT) can be significantly prolonged, an effect that is related to aIIa and aXa activity. The volume of distribution of LMWHs is of the same order of magnitude as that of the plasma volume. The mean retention time of aXa activity varies from 5.2 (dalteparin) to approximately 7 h (enoxaparin, nadroparin). Bioavailability of prophylactic doses of LMWHs ranges from 86% (dalteparin) to 98% (enoxaparin, nadroparin). PK parameters appear to be minimally affected by a patient's age. The Clplasma is different for each LMWH: 16 mL/min enoxaparin, 21 mL/min nadroparin, 33 mL/min dalteparin, 19 mL/min reviparin, and 22 mL/min tinzaparin. Accumulation of product has been observed for almost all LMWHs in patients with renal insufficiency. LMWHs are effective and safe for treatment or prophylaxis of venous thromboembolism during pregnancy, because they do not cross the placenta. No data are available regarding the passage of LMWHs into the milk in lactating women. Although LMWHs are also effective in prevention and treatment of thromboembolic disease in children, optimal use of these agents in pediatric patients has not been determined. In summary, the PD and PK of LMWHs have been well documented and have demonstrated that LMWHs have a more predictable response, a greater bioavailability, and a longer aXa t1/2 than unfractionated heparin. However, their distribution of MW affects their physicochemical and biological properties, as well as PK characteristics. The concept of aXa/aIIa ratio (determined in vitro) does not account for the differing PK of aXa and aIIIa activity in circulating blood.

This chapter about antithrombotic therapy for coronary artery disease (CAD) is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: For patients presenting with non-ST-segment elevation (NSTE) acute coronary syndrome (ACS), we recommend immediate and then daily oral aspirin (Grade 1A). For patients with an aspirin allergy, we recommend immediate treatment with clopidogrel, 300-mg bolus po, followed by 75 mg/d indefinitely (Grade 1A). In all NSTE ACS patients in whom diagnostic catheterization will be delayed or when coronary bypass surgery will not occur until>> 5 days, we recommend clopidogrel as bolus therapy (300 mg), followed by 75 mg/d for 9 to 12 months in addition to aspirin (Grade 1A). In NSTE ACS patients in whom angiography will take place within 24 h, we suggest beginning clopidogrel after the coronary anatomy has been determined (Grade 2A). For patients who have received clopidogrel and are scheduled for coronary bypass surgery, we recommend discontinuing clopidogrel for 5 days prior to the scheduled surgery (Grade 2A). In moderate- to high-risk patients presenting with NSTE ACS, we recommend either eptifibatide or tirofiban for initial (early) treatment in addition to treatment with aspirin and heparin (Grade 1A). For the acute treatment of NSTE ACS, we recommend low molecular weight heparins over unfractionated heparin (UFH) [Grade 1B] and UFH over no heparin therapy use with antiplatelet therapies (Grade 1A). We recommend against the direct thrombin inhibitors as routine initial antithrombin therapy (Grade 1B). For patients after myocardial infarction, after ACS, and with stable CAD, we recommend aspirin in doses from 75 to 325 mg as initial therapy and in doses of 75 to 162 mg as indefinite therapy (Grade 1A). For patients with contraindications to aspirin, we recommend long-term clopidogrel (Grade 1A). For primary prevention in patients with at least moderate risk for a coronary event, we recommend aspirin, 75 to 162 mg/d, over either no antithrombotic therapy or vitamin K antagonist (VKA) [Grade 2A]; for patients at particularly high risk of events in whom the international normalized ratio (INR) can be monitored without difficulty, we suggest low-dose VKA (target INR, 1.5) [Grade 2A].

OBJECTIVE

The ExTRACT-TIMI 25 (Enoxaparin and Thrombolysis Reperfusion for Acute Myocardial Infarction Treatment-Thrombolysis In Myocardial Infarction 25) trial provided the opportunity to evaluate the impact of renal dysfunction on outcomes in patients with ST-segment elevation myocardial infarction (STEMI) and compare enoxaparin (ENOX) and unfractionated heparin (UFH).

BACKGROUND

It is unclear how renal dysfunction influences the balance between benefit and risk of antithrombotic therapy.

METHODS

In the ExTRACT-TIMI 25 trial, 20,479 patients were randomized to UFH or ENOX. A reduced ENOX dose was administered to patients age>> or =75 years and those with an estimated creatinine clearance (CrCl) <30 ml/min.

RESULTS

A powerful relationship was observed between the severity of renal dysfunction (per 10 ml/min decrement in CrCl) and death, stroke, intracranial hemorrhage, and major and minor bleeding (p < 0.001 for each). There was a progressive increase in the treatment benefit with ENOX on death or nonfatal myocardial infarction (p < 0.01) with better renal function. Net clinical benefit (death, nonfatal MI, or nonfatal major bleeding) was significantly superior with ENOX (p < 0.001) for patients with a CrCl >60 ml/min (79.1% of the study population). Major bleeding and intracranial hemorrhage did not differ for patients with preserved renal function (CrCl >90 ml/min), but in those with renal dysfunction there was a progressively greater increase in the risk of major and minor bleeding with ENOX.

CONCLUSIONS

Enoxaparin was superior to UFH for the majority of subjects. With more severe renal dysfunction, the net clinical benefit between ENOX and UFH did not differ, despite the rise in adverse events in both treatment groups. Future studies should take renal dysfunction into account when assessing antithrombotic regimens.

The objective of the present study was to evaluate whether integrated (18)F-FDG PET/MR imaging could improve the diagnostic workup in patients with cardiac masses.

METHODS

Twenty patients were prospectively assessed using integrated cardiac (18)F-FDG PET/MR imaging: 16 patients with cardiac masses of unknown identity and 4 patients with cardiac sarcoma after surgical therapy. All scans were obtained on an integrated 3-T PET/MR device. The MR protocol consisted of half Fourier acquisition single-shot turbo spin-echo sequence, cine, and T2-weighted images as well as T1-weighted images before and after injection of gadobutrol. PET data were acquired simultaneously with the MR scan after injection of 199 ± 58 MBq of (18)F-FDG. Patients were prepared with a high-fat, low-carbohydrate diet in a period of 24 h before the examination, and 50 IU/kg of unfractionated heparin were administered intravenously 15 min before (18)F-FDG injection.

RESULTS

Cardiac masses were diagnosed as follows: metastases, 3; direct tumor infiltration via pulmonary vein, 1; local relapse of primary sarcoma after surgery, 2; Burkitt lymphoma, 1; scar/patch tissue after surgery of primary sarcoma, 2; myxoma, 4; fibroelastoma, 1; caseous calcification of mitral annulus, 3; and thrombus, 3. The maximum standardized uptake value (SUVmax) in malignant lesions was significantly higher than in nonmalignant cases (13.2 ± 6.2 vs. 2.3 ± 1.2, P = 0.0004). When a threshold of 5.2 or greater was used, SUVmax was found to yield 100% sensitivity and 92% specificity for the differentiation between malignant and nonmalignant cases. T2-weighted hyperintensity and contrast enhancement both yielded 100% sensitivity but a weak specificity of 54% and 46%, respectively. Morphologic tumor features as assessed by cine MR imaging yielded 86% sensitivity and 92% specificity. Consent interpretation using all available MR features yielded 100% sensitivity and 92% specificity. A Boolean 'AND' combination of an SUVmax of 5.2 or greater with consent MR image interpretation improved sensitivity and specificity to 100%.

CONCLUSIONS

In selected patients, (18)F-FDG PET/MR imaging can improve the noninvasive diagnosis and follow-up of cardiac masses.

BACKGROUND

The efficacy and safety of the anticoagulant rivaroxaban for the treatment and secondary prevention of deep-vein thrombosis and pulmonary embolism has been shown in phase 3 trials. However, data about rivaroxaban use in routine clinical practice are needed.

METHODS

XA inhibition with rivaroxaban for Long-term and Initial Anticoagulation in venous thromboembolism (XALIA) was a multicentre, international, prospective, non-interventional study of patients with deep-vein thrombosis, done in hospitals and community care centres in 21 countries. The study investigated the safety and effectiveness of rivaroxaban compared with standard anticoagulation therapy (initial treatment with unfractionated heparin, low-molecular-weight heparin, or fondaparinux, usually overlapping with and followed by a vitamin K antagonist) for at least 3 months. Eligible patients were adults (aged ≥18 years) with an objectively confirmed diagnosis of deep-vein thrombosis, and an indication to receive anticoagulation treatment for at least 3 months. Following approval of rivaroxaban for the pulmonary embolism indication, patients with deep-vein thrombosis and concomitant pulmonary embolism were also eligible; however, those with isolated pulmonary embolism were not included. Type, dose, and duration of therapy for each patient were at the physician's discretion. The primary effectiveness and safety outcomes were major bleeding, recurrent venous thromboembolism, and all-cause mortality. Propensity score-adjusted analyses were done to account for potential imbalances between groups. This study is registered with ClinicalTrials.gov, number NCT01619007.

RESULTS

Between June 26, 2012, and March 31, 2014, 5142 patients were enrolled. The safety population (all patients who received at least one dose of the anticoagulant of interest) comprised 2619 patients in the rivaroxaban group and 2149 in the standard anticoagulant therapy group. Patients in the rivaroxaban group were younger and fewer had active cancer or concomitant pulmonary embolism than those in the standard anticoagulation group. In the propensity score-adjusted population, the frequency of major bleeding was 0·8% (19/2505) in the rivaroxaban group and 2·1% (43/2010) in the standard anticoagulation group, with a propensity score-adjusted hazard ratio (HR) of 0·77 (95% CI 0·40-1·50); p=0·44. The frequency of recurrent venous thromboembolism was 1·4% (36/2505) in the rivaroxaban group and 2·3% (47/2010) in the standard anticoagulation group (propensity score-adjusted HR 0·91 [95% CI 0·54-1·54], p=0·72). The all-cause mortality frequency was 0·4% (11/2505) in the rivaroxaban group and 3·4% (69/2010) in the standard anticoagulation group (propensity score-adjusted HR 0·51 [95% CI 0·24-1·07], p=0·074). The incidence of treatment-emergent adverse events in the safety population was similar between the two groups (944 [36·0%] of 2619 in the rivaroxaban group vs 805 [37·5%] of 2149 in the standard anticoagulation group).

CONCLUSIONS

In routine clinical practice, rivaroxaban-treated patients had a lower risk profile at baseline than those treated with standard anticoagulation. Propensity score-adjusted results confirm that rivaroxaban is a safe and effective alternative to standard anticoagulation therapy in a broad range of patients. Rates of major bleeding and recurrent venous thromboembolism were low in rivaroxaban-treated patients and consistent with phase 3 findings.

BACKGROUND

Bayer HealthCare Pharmaceuticals and Janssen Research & Development, LLC.

This guidance document focuses on the diagnosis and treatment of venous thromboembolism (VTE). Efficient, cost effective diagnosis of VTE is facilitated by combining medical history and physical examination with pre-test probability models, D dimer testing and selective use of confirmatory imaging. Clinical prediction rules, biomarkers and imaging can be used to tailor therapy to disease severity. Anticoagulation options for acute VTE include unfractionated heparin, low molecular weight heparin, fondaparinux and the direct oral anticoagulants (DOACs). DOACs are as effective as conventional therapy with LMWH and vitamin K antagonists. Thrombolytic therapy is reserved for massive pulmonary embolism (PE) or extensive deep vein thrombosis (DVT). Inferior vena cava filters are reserved for patients with acute VTE and contraindications to anticoagulation. Retrievable filters are strongly preferred. The possibility of thoracic outlet syndrome and May-Thurner syndrome should be considered in patients with subclavian/axillary and left common iliac vein DVT, respectively in absence of identifiable triggers. The optimal duration of therapy is dictated by the presence of modifiable thrombotic risk factors. Long term anticoagulation should be considered in patients with unprovoked VTE as well as persistent prothrombotic risk factors such as cancer. Short-term therapy is sufficient for most patients with VTE associated with transient situational triggers such as major surgery. Biomarkers such as D dimer and risk assessment models such the Vienna risk prediction model offer the potential to customize VTE therapy for the individual patient. Insufficient data exist to support the integration of bleeding risk models into duration of therapy planning.

We read with interest the International Society on Thrombosis and Hemostasis interim guidance on recognition and management of coagulopathy in COVID-19 (1). We applaud this group's efforts in releasing a timely article on the pandemic impacting all regions of the globe. While we agree that this interim guidance addresses important considerations for monitoring the disease process, we believe that the proposed treatment strategy of prophylactic low molecular weight heparin (LMWH) to treat severe COVID-19 coagulopathy is an unconvincing strategy. Patients that are critically ill with COVID-19 have hallmark signs of disseminated intravascular coagulation (DIC)(2), and as noted in the ISTH interim guidance and our own clinical practice, thrombosis is the overwhelming phenotype with rare bleeding complications. We address this concern with the existing data on the severe hypercoagulable state of COVID-19 victims and advocate for consideration of systemic anticoagulation with unfractionated heparin to prevent life threatening micro- and macrovascular thrombosis to mitigate their associated consequences, up to and including progression of respiratory and organ failure.

Venous thromboembolism remains an important cause of maternal mortality. In a randomised open study, 44 pregnant women with confirmed previous or current thromboembolism were randomised to receive either low-molecular-weight heparin, dalteparin (N = 21) once daily subcutaneously or unfractionated sodium heparin (UF heparin, N = 23) twice daily subcutaneously for thromboprophylaxis during pregnancy and puerperium. Bone mineral density (BMD) in the lumbosacral spine was measured with dual X-ray absorptiometry (DEXA) 1, 6, 16, 52 weeks and, if possible, 3 years after delivery. BMD values were also compared with those of healthy, delivered women (N = 19). Mean BMD of the lumbar spine was significantly lower in the unfractionated heparin group compared with the dalteparin and with the control groups (repeated measures ANOVA p = 0.02). BMD in the dalteparin group did not differ from BMD of healthy delivered women. Multiple logistic regression analysis revealed that therapy was the only independent factor influencing BMD at weeks 16 and 52. Therefore we recommend use of dalteparin instead of UF heparin for long-term thromboprophylaxis during and after pregnancy.

OBJECTIVE

Studies have shown improved survival in cancer patients treated with low molecular weight heparins (LMWHs). Tumors depend on an expanding vasculature, and heparins may affect vessel growth and function. We investigated the effect of heparins differing in Mr on selected endothelial cell properties.

RESULTS

Human umbilical vein endothelial cells were cultured with fibroblast growth factor-2 and heparins differing in Mr. Cell proliferation was assessed by [3H]thymidine incorporation, and vascular organization was assessed by in vitro assays. Maximum inhibition of 94+/-2% was observed with 6-kDa LMWH, greater than the inhibition seen with unfractionated heparin (58+/-8%) or 3-kDa LMWH (60+/-9%, P=0.02 for both). No inhibition of proliferation was observed with heparin tetrasaccharide, octasaccharide, or pentasaccharide (fondaparinux). Three- and 6-kDa fractions decreased endothelial tube formation in Matrigel to 58+/-15% and 67+/-9% (P<0.05), respectively, of that with fibroblast growth factor-2, whereas no inhibition was observed with unfractionated heparin, tetrasaccharide, pentasaccharide, or octasaccharide. LMWH (6 kDa) also inhibited vessel formation in a placental explant.

CONCLUSIONS

Heparin inhibition of endothelial cell proliferation and organization requires a chain length of >8 saccharide units, with maximal inhibition at Mr of 6 kDa. This Mr dependence differs from that required for anticoagulant activity.

We have compared the non-specific binding of unfractionated heparin (UFH) with that of low molecular weight heparin (LMWH) to plasma proteins both ex-vivo and in-vitro. Non-specific binding to plasma proteins was assessed by comparing the heparin levels measured as anti-factor Xa activity before and after the addition of low affinity heparin, which is essentially devoid of anti-factor Xa activity, in order to displace heparin bound to plasma proteins. For the ex-vivo studies, we compared the recovery of UFH and a LMWH (ardeparin) from the plasma of patients participating in a randomized trial of post-operative venous thrombosis prophylaxis. For the in-vitro studies, we compared the recovery of UFH and 4 different LMWHs when added to the plasma from healthy volunteers and from patients with suspected venous thromboembolic disease. The results indicate that the recovery of LMWH is much less affected by nonspecific binding to plasma proteins both ex-vivo and in-vitro. In addition, there are differences between the LMWHs with respect to their plasma protein-binding.

OBJECTIVE

The goal of this study was to evaluate glycoprotein IIb/IIIa inhibition with eptifibatide when administered with indirect thrombin inhibition as compared with monotherapy with direct thrombin inhibition with bivalirudin among patients with non-ST-segment elevation acute coronary syndromes (ACS).

BACKGROUND

The optimal combination of antiplatelet and antithrombin regimens that maximizes efficacy and minimizes bleeding among patients with non-ST-segment elevation ACS undergoing percutaneous coronary intervention (PCI) is unclear.

METHODS

A total of 857 patients with non-ST-segment elevation ACS were assigned randomly to eptifibatide + reduced dose unfractionated heparin (n = 298), eptifibatide + reduced-dose enoxaparin (n = 275), or bivalirudin monotherapy (n = 284).

RESULTS

Among angiographically evaluable patients (n = 754), the primary end point of post-PCI coronary flow reserve was significantly greater with bivalirudin (1.43 vs. 1.33 for pooled eptifibatide arms, p = 0.036). Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade more often was normal with eptifibatide treatment compared with bivalirudin (57.9% vs. 50.9%, p = 0.048). The duration of ischemia on continuous Holter monitoring after PCI was significantly longer among patients treated with bivalirudin (169 vs. 36 min, p = 0.013). There was no excess of TIMI major bleeding among patients treated with eptifibatide compared with bivalirudin (0.7%, n = 4 vs. 0%, p = NS), but TIMI minor bleeding was increased (2.5% vs. 0.4%, p = 0.027) as was transfusion (4.4% to 0.4%, p < 0.001).

CONCLUSIONS

Among moderate- to high-risk patients with ACS undergoing PCI, coronary flow reserve was greater with bivalirudin than eptifibatide. Eptifibatide improved myocardial perfusion and reduced the duration of post-PCI ischemia but was associated with higher minor bleeding and transfusion rates. Ischemic events and biomarkers for myonecrosis, inflammation, and thrombin generation did not differ between agents.

The efficacy and safety of a low-molecular-weight (LMW) heparin fraction in preventing postoperative venous thrombo-embolism, was assessed in a double blind, randomly allocated trial, and in an 'open' study. Of 395 patients included in the double blind trial, 199 received unfractionated (UF) calcium heparin, and 196 the LMW heparin fraction. The data were analysed on an 'intention to treat' basis. The two groups were well matched for risk factors which could predispose to the development of venous thrombosis. Fifteen (7.5 per cent) of one hundred and ninety-nine patients receiving UF heparin, and five (2.5 per cent) of one hundred and ninety-six patients in the LMW heparin group developed DVT (P less than 0.05). There was no significant difference between the two groups in terms of excessive incisional or total blood loss during surgery, postoperative drainage or wound haematoma formation. Of 910 patients included in the 'open' study who received a single injection of LMW heparin every day, 30 (3.2 per cent) died during the postoperative period; in none of the autopsied patients were pulmonary emboli detected. Thirty-one (3.4 per cent) patients developed isotopic DVT; twenty-seven (2.9 per cent) were receiving prophylaxis at the time the DVT was diagnosed. Thirty-six (3.9 per cent) patients developed wound haematoma; twenty-five (12.4 per cent) of those were in the two hundred and one undergoing surgery for gynaecological conditions, and eleven (1.5 per cent) in the seven hundred and nine patients having general abdominal surgery. This difference is statistically significant (P less than 0.001). The results of a double blind trial indicate that a single daily injection of 1850 APTT units (7500 antifactor Xa units) of a LMW heparin is more effective than 10 000 APTT units of commercially available UF heparin in preventing postoperative DVT. The findings of the 'open' study suggest that this regimen also provides an effective prophylaxis against post-operative major pulmonary embolism.

BACKGROUND

The clinical benefit of thrombolytic treatment over heparin in patients with pulmonary embolism without hemodynamic compromise remains controversial. In these patients bolus tenecteplase has the potential to provide an effective and safe thrombolysis.

METHODS

We evaluated the effect of tenecteplase on right ventricle dysfunction (RVD) assessed by echocardiography in hemodynamically stable patients with PE in a multicenter, randomized, double-blind, placebo-controlled study. RVD was defined as right/left ventricle end-diastolic dimension ratio >1 in the apical 4-chamber view. Patients were randomized to receive weight-adjusted single-bolus tenecteplase or placebo. All patients received unfractionated heparin. Reduction of RVD at 24 hours was the primary efficacy end-point and was evaluated by an independent committee unaware of treatment allocation.

RESULTS

Overall, 58 patients were randomized. Echocardiograms were adequate for efficacy analysis in 51 patients, 23 randomized to tenecteplase and 28 to placebo. The reduction of right to left ventricle end-diastolic dimension ratio at 24 hours was 0.31+/-0.08 in patients randomized to tenecteplase as compared to 0.10+/-0.07 in patients randomized to placebo (p=0.04). One patient randomized to tenecteplase suffered a clinical event (recurrent pulmonary embolism) in comparison to three patients randomized to placebo (1 recurrent pulmonary embolism; 1 clinical deterioration and 1 non pulmonary embolism-related death). Two non fatal major bleedings occurred with tenecteplase (1 intracranial) and one with placebo.

CONCLUSIONS

In hemodynamically stable patients with PE, treatment with single bolus tenecteplase is feasible at the same dosages used for acute myocardial infarction and is associated with reduction of RVD at 24 hours. Whether this benefit is associated with an improved clinical outcome without excessive bleeding is currently explored in a large clinical trial.

TFPI is a potent inhibitor of the extrinsic coagulation system constitutively synthesized by endothelial cells. A major portion of intravascular TFPI is stored associated with endothelial cells. and administration of unfractionated heparin (UFH) in vivo causes a prompt mobilization of TFPI into the circulation. The present study was conducted to investigate how UFH affected the synthesis, secretion and anticoagulant potency of TFPI in endothelial cells in vitro. A spontaneously transformed immortal endothelial cell line was used (ECV304). Stimulation of ECV304 cells with UFH caused a prompt dose-dependent (0-5 IU UFH/ml) release of TFPI to the medium accompanied by no change of TFPI at the surface membrane assessed by immunocytochemical methods. Northern blot analysis revealed two mRNA transcripts for TFPI with a molecular size of 1.4 kb and 4.4 kb, respectively. Stimulation of ECV304 cells for 24 hrs with various concentrations of UFH caused a dose-dependent increase of TFPI in the medium (6.2-29.6 ng/10(6) cells within the concentration range 0-10 IU/ml). A similar dose-dependent increase in the expression of both TFPI mRNA species was observed. Long-term incubation of ECV304 cells with 5.0 IU/ml UFH caused a 5-10 fold increase in the TFPI concentration accumulated in the medium over 48 hrs. The increased TFPI mRNA expression induced by UFH appeared already after 10 min, peaked after 2-4 hrs, remained augmented throughout the entire period of UFH exposure, and preceded the synthesis-dependent increase in TFPI release by 2-4 hrs. The procoagulant activity of the cells was downregulated by 36% and the contribution of TFPI to the anticoagulant potency of ECV304 cells was moderately increased after 24 hrs heparin stimulation. It is suggested that these mechanisms are of major importance for the anticoagulant function of heparins.

Tissue factor pathway inhibitor (TFPI), the major downregulator of procoagulant activity of the tissue factor-factor VIIa complex (TF. FVIIa), is synthesized and constitutively secreted by endothelial cells (ECs). Here we describe the in vitro effects of heparin on the cellular localization, gene expression, and release of TFPI in human ECs in culture. Both unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH; Fragmin) time-dependently induced a significant enhanced secretion of TFPI, paralleled by a redistribution and increase of TFPI on the cell surface and a decrease of intracellular TFPI. Immunogold electron microscopy showed the presence of clusters of TFPI, both on the plasmalemma proper and within cell-surface opened caveolae/enlarged caveolar profiles. Activation of FX by TF. FVIIa on ECs treated with endotoxin was inhibited by both heparins but to a higher extent by LMWH. Inhibition of protein synthesis by cycloheximide did not reduce the release of TFPI induced by heparin. Long-term incubation (48 hours) resulted in a time-dependent enhanced production of TFPI. After the first 4 to 8 hours, depletion of intracellular TFPI was observed, more significantly with UFH. Northern blot analysis of TFPI mRNA also showed a decrease of the 1.4-kb transcript after 4 hours of incubation with UFH, followed by recovery and an increase over the control level after 24 hours. Incubation of ECs with phorbol ester (PMA) significantly enhanced the secretion of TFPI and increased its activity on the cell surface, probably by preventing invagination of caveolae. Heparin-stimulated release of TFPI decreased significantly in the presence of PMA to a level that was 2. 4 times lower than the expected additive value for PMA and UFH separately. Pretreatment of ECs with PMA suppressed a subsequent response to heparin. Altogether, our results suggest that the heparin-induced release of TFPI might involve a more specific mechanism(s) than the previously hypothesized simple displacement of TFPI from the cell surface glycocalyx. We assume that the increased secretion and redistribution of cellular TFPI induced by heparins in ECs in culture can play an important role in the modulation of the anticoagulant properties of the endothelium.

The adhesion of sickle erythrocytes to vascular endothelium is important to the generation of vascular occlusion. Interactions between sickle cells and the endothelium use several cell adhesion molecules. We have reported that sickle cell adhesion to endothelial cells under static conditions involves P-selectin. Others have shown that sickle cell adhesion is decreased by unfractionated heparin, but the molecular target of this inhibition has not been defined. We postulated that the adhesion of sickle cells to P-selectin might be the pathway blocked by unfractionated heparin. In this report we demonstrate that the flow adherence of sickle cells to thrombin-treated human vascular endothelial cells also uses P-selectin and that this component of adhesion is inhibited by unfractionated heparin. We also demonstrate that sickle cells adhere to immobilized recombinant P-selectin under flow conditions. This adhesion too was inhibited by unfractionated heparin, in a concentration range that is clinically attainable. These findings and the general role of P-selectin in initiating adhesion of blood cells to the endothelium suggest that unfractionated heparin may be useful in preventing painful vascular occlusion. A clinical trial to test this hypothesis is indicated.

Low molecular weight heparins (LWMH) are the preferred initial treatment for many thromboembolic disorders but are renally excreted and relatively contraindicated in patients with renal failure because of concerns of increased bleeding risks. The purpose of this study was to evaluate the safety and efficacy of LMWH compared with unfractionated heparin (UFH) for preventing thrombosis of the extracorporeal dialysis circuit. Studies were identified with the use of MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and FirstSearch; reference lists were reviewed; and pharmaceutical companies were contacted. Randomized, controlled trials that compared an LMWH with another anticoagulant during hemodialysis in patients with ESRD and reported at least one of bleeding, extracorporeal circuit thrombosis, or anti-Xa levels were chosen. Two reviewers independently extracted data on methodologic quality, study design, clinical outcomes, and anti-Xa levels. Seventeen trials were included in this systematic review, 11 of which were included in the meta-analysis. It was found that LMWH did not significantly affect the number of bleeding events (relative risk, 0.96; 95% confidence interval [CI], 0.27 to 3.43), bleeding assessed by vascular access compression time (weighted mean difference, -0.87; 95% CI, -2.75 to 1.02), or extracorporeal circuit thrombosis (relative risk, 1.15; 95% CI, 0.70 to 1.91) as compared with UFH. LMWH seem to be as safe as UFH in terms of bleeding complications and as effective as UFH in preventing extracorporeal circuit thrombosis. However, inferences from these trials assessing anticoagulation for patients who undergo hemodialysis will continue to be weak until larger, more rigorous randomized trials are conducted.

OBJECTIVE

To study the maternal and fetal outcome in treated antiphospholipid syndrome (APS) pregnancies.

METHODS

Sixty pregnancies in 47 APS patients (11 primary and 36 secondary) were followed in a multidisciplinary clinic. Patients testing antiphospholipid antibody positive and having a history of recurrent miscarriages were treated with low-dose aspirin (75 mg) daily. Patients with APS and a previous history of thrombotic events were treated with subcutaneous unfractionated or low molecular weight heparin and low-dose aspirin (75 mg) daily.

RESULTS

The live birth rate increased from 19% of their previous non-treated pregnancies to 70% despite a high incidence of obstetric and fetal complications: pre-eclampsia (18%), prematurity (43%), fetal distress (50%) and intrauterine growth retardation (31%). Two predictors of fetal outcome were observed: the previous obstetric history and the presence of thrombocytopenia. Seven pregnancies (12%) were complicated by thrombotic events during pregnancy or during the puerperium. There were no thrombotic events in those receiving a low molecular weight heparin regimen.

CONCLUSIONS

Close obstetric monitoring by a multidisciplinary team and the use of antithrombotic therapy was effective in reducing the fetal wastage in APS pregnancies despite a high incidence of obstetric and fetal complications.

This chapter is devoted to antithrombotic therapy for peripheral artery occlusive disease as part of the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see the "Grades of Recommendation" chapter by Guyatt et al, CHEST 2008; 133:123S-131S). Among the key recommendations in this chapter are the following: We recommend lifelong antiplatelet therapy in comparison to no antiplatelet therapy in pulmonary artery disease (PAD) patients with clinically manifest coronary or cerebrovascular disease (Grade 1A), and also in those without clinically manifest coronary or cerebrovascular disease (Grade 1B). In patients with PAD and intermittent claudication, we recommend against the use of anticoagulants (Grade 1A). For patients with moderate to severe disabling intermittent claudication who do not respond to exercise therapy, and who are not candidates for surgical or catheter-based intervention, we recommend cilostazol (Grade 1A). We suggest that clinicians not use cilostazol in those with less-disabling claudication (Grade 2A). In patients with short-term (< 14 days) arterial thrombosis or embolism, we suggest intraarterial thrombolytic therapy (Grade 2B), provided they are at low risk of myonecrosis and ischemic nerve damage developing during the time to achieve revascularization. For patients undergoing major vascular reconstructive procedures, we recommend IV unfractionated heparin (UFH) prior to the application of vascular cross clamps (Grade 1A). For all patients undergoing infrainguinal arterial reconstruction, we recommend aspirin (75-100 mg, begun preoperatively) [Grade 1A]. For routine autogenous vein infrainguinal bypass, we recommend aspirin (75-100 mg, begun preoperatively) [Grade 1A]. For routine prosthetic infrainguinal bypass, we recommend aspirin (75-100 mg, begun preoperatively) [Grade 1A]. In patients undergoing carotid endarterectomy, we recommend that aspirin, 75-100 mg, be administered preoperatively and continued indefinitely (75-100 mg/d) [Grade 1A]. In nonoperative patients with asymptomatic carotid stenosis (primary or recurrent), we suggest that dual antiplatelet therapy with aspirin and clopidogrel be avoided (Grade 1B). For all patients undergoing lower-extremity balloon angioplasty (with or without stenting), we recommend long-term aspirin, 75-100 mg/d (Grade 1C).

OBJECTIVE

To compare two methods of determining a therapeutic range of activated partial thromboplastin time (aPTT) results.

METHODS

Cohort studies.

METHODS

Referral teaching hospital.

METHODS

Inpatients who received unfractionated heparin intravenously for venous thromboembolic disease.

METHODS

A therapeutic range determined by aPTT ratios of 1.5 to 2.5 times the control value as compared with a therapeutic range determined by protamine titration heparin levels of 0.2 to 0.4 U/mL.

RESULTS

For all aPTT reagents studied, a ratio of 1.5 times the control value is much less than a minimum protamine titration heparin level of 0.2 U/mL. Various manufacturers' aPTT reagents and reagent lots from the same manufacturer show considerable variation in response to heparin and therefore have different therapeutic ranges.

CONCLUSIONS

A different dose of heparin would be required to produce an aPTT ratio of 1.5 times the control value, depending on the reagent used. Establishing a therapeutic range for aPTT results using protamine titration heparin levels of 0.2 to 0.4 U/mL as a reference standard is practical and compensates for the variable response of aPTT reagents to heparin.

This chapter about antithrombotic therapy for peripheral arterial occlusive disease is part of the seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs, and Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004;126:179S-187S). Among the key recommendations in this chapter are the following: For patients with chronic limb ischemia, we recommend lifelong aspirin therapy in comparison to no antiplatelet therapy in patients with clinically manifest coronary or cerebrovascular disease (Grade 1A) and in those without clinically manifest coronary or cerebrovascular disease (Grade 1C+). We recommend clopidogrel over no antiplatelet therapy (Grade 1C+) but suggest that aspirin be used instead of clopidogrel (Grade 2A). For patients with disabling intermittent claudication who do not respond to conservative measures and who are not candidates for surgical or catheter-based intervention, we suggest cilostazol (Grade 2A). We suggest that clinicians not use cilostazol in patients with less-disabling claudication (Grade 2A). In these patients, we recommend against the use of pentoxifylline (Grade 1B). We suggest clinicians not use prostaglandins (Grade 2B). In patients with intermittent claudication, we recommend against the use of anticoagulants (Grade 1A). In patients with acute arterial emboli or thrombosis, we recommend treatment with immediate systemic anticoagulation with unfractionated heparin (UFH) [Grade 1C]. We also recommend systemic anticoagulation with UFH followed by long-term vitamin K antagonist (VKA) in patients with embolism [Grade 1C]). For patients undergoing major vascular reconstructive procedures, we recommend UFH at the time of application of vascular cross-clamps (Grade 1A). In patients undergoing prosthetic infrainguinal bypass, we recommend aspirin (Grade 1A). In patients undergoing infrainguinal femoropopliteal or distal vein bypass, we suggest that clinicians do not routinely use a VKA (Grade 2A). For routine patients undergoing infrainguinal bypass without special risk factors for occlusion, we recommend against VKA plus aspirin (Grade 1A). For those at high risk of bypass occlusion and limb loss, we suggest VKA plus aspirin (Grade 2B). In patients undergoing carotid endarterectomy, we recommend aspirin preoperatively and continued indefinitely (Grade 1A). In nonoperative patients with asymptomatic or recurrent carotid stenosis, we recommend lifelong aspirin (Grade 1C+). For all patients undergoing extremity balloon angioplasty, we recommend long-term aspirin (Grade 1C+).