Percentage of Inadequate Phlebograms and Observer Agreement in Thromboprophylactic Multicenter Trials Using Standardized Methodology and Central Assessment

Epidemiology of total hip and knee replacement: a cross-sectional study

Objective:

To describe the epidemiologic characteristics and adverse events of patients submitted to total hip and total knee replacement.

Methods:

A cross-sectional study retrospectively assessing medical chart data of all total hip and total knee replacements performed at a private hospital, between January 2007 and December 2010 Patients submitted to total hip and total knee replacement, with consent of surgeons were included. Incomplete records and/or missing data of the hospital database were excluded. The categorical variables analyzed were age, gender, type of arthroplasty (primary or secondary), type of procedure, duration of surgery, use of drains, risk of infection, compliance to protocol for prevention of deep venous thrombosis and embolism pulmonary, and compliance to the protocol for prevention of infection. The outcomes assessed were adverse events after surgery.

Results:

A total of 510 patients were included; in that, 166 admissions for knee replacements (92 male) and 344 admissions for hip replacements (176 female). The mean age of patients was 71 years (range 31-99 years). Adverse events were reported in 76 patients (14.9%); there was no correlation between assessed variables and number of complications.

Conclusion:

The results showed no individual factors favoring complications in patients submitted to total hip and total knee replacement; hence, surgeons should consider prophylaxis to avoid complications.

Rivaroxaban versus enoxaparin for thromboprophylaxis after total hip or knee arthroplasty: a meta-analysis of randomized controlled trials

PURPOSE

Rivaroxaban is a newly developed oral medicine that direct inhibits factor Xa for the prevention and treatment of thromboembolic disorders. The objective of this study was to compare the efficacy and safety of rivaroxaban versus enoxaparin, a medicine routinely used for thromboprophylaxis after total hip or knee arthroplasty.

METHODS

We performed a meta-analysis of relevant randomized controlled trials (RCTs) identified in PubMed, Cochrane library, and Embase. The primary efficacy outcome for our meta-analysis was total venous thromboembolism (VTE) and all-cause mortality. The primary safety outcome was bleeding events, which were categorized as major, clinically relevant non-major, or minor events.

RESULTS

Eight RCTs, involving 15,586 patients, were included in our meta-analysis. Compared to enoxaparin, thromboprophylaxis with rivaroxaban was associated with significantly fewer VTE and all-cause mortality [9,244 patients, risk ratio (RR) 0.56, 95% confidence interval (CI) 0.39-0.80] cases and a similar incidence of bleeding cases (major bleeding events: 13,384 patients, RR 1.65, 95% CI 0.93-2.93; clinically relevant non-major bleeding events: 13,384 patients, RR 1.21, 95% CI 0.98-1.50; total bleeding events, 13,384 patients, RR 1.10, 95% CI 0.97-1.24). The total hip or knee arthroplasty subgroup analysis revealed consistent efficacy and safety findings.

CONCLUSIONS

Rivaroxaban was more effective than the recommended dose of enoxaparin and had a similar safety profile for thromboprophylaxis after hip and knee arthroplasty.

Overview of current venous thromboembolism protocols in hip reconstruction

Venous thromboembolic disease continues to be a serious complication of total-hip arthroplasty. The use of anticoagulant drugs for preventing this complication has repeatedly been proven to be useful. This article reviews the current evidence-based recommendations for anticoagulant prophylaxis after total-hip arthroplasty and provides insight into the current areas of active research and controversy.

Oral thrombin inhibitor dabigatran etexilate vs North American enoxaparin regimen for prevention of venous thromboembolism after knee arthroplasty surgery

Dabigatran, an oral once-daily unmonitored thrombin inhibitor, has been tested elsewhere using enoxaparin 40 mg once daily. We used the North American enoxaparin 30 mg BID regimen as the comparator. This was a double-blind, centrally randomized trial. Unilateral total knee arthroplasty patients were randomized to receive oral dabigatran etexilate 220 or 150 mg once daily, or enoxaparin 30 mg SC BID after surgery, blinded. Dosing stopped at contrast venography, 12 to 15 days after surgery. Among 1896 patients, dabigatran 220 and 110 mg showed inferior efficacy to enoxaparin (venous thromboembolism rates of 31% [P = .02 vs enoxaparin], 34% [P < .001 vs enoxaparin], and 25%, respectively). Bleeding rates were similar, and no drug-related hepatic illness was recognized. Dabigatran, effective compared to once-daily enoxaparin, showed inferior efficacy to the twice-daily North American enoxaparin regimen, probably because of the latter's more intense and prolonged dosing.

Partial factor IXa inhibition with TTP889 for prevention of venous thromboembolism: an exploratory study

BACKGROUND

Inhibitors of factor (F) IXa show potent antithrombotic activity with a low risk of bleeding in preclinical models. We investigated the anticoagulant potential of oral TTP889, a small molecule that inhibits up to 90% of FIXa activity at therapeutic doses, using a clinical model of extended prophylaxis in hip fracture surgery (HFS).

METHODS

In this multicenter, randomized, double-blind study, 261 patients received oral TTP889 (300 mg once daily) or placebo starting 6-10 days after HFS, and standard thromboprophylaxis for 5-9 days. Treatment was continued for 3 weeks and all patients then underwent mandatory bilateral venography. The primary efficacy outcome was venous thromboembolism (VTE; venographic or symptomatic deep vein thrombosis or pulmonary embolism) during treatment, and it was evaluated centrally by an independent adjudication panel. The main safety outcome was bleeding (major, clinically relevant non-major, and minor events).

RESULTS

Two hundred and twelve patients with an evaluable venogram were included in the efficacy analysis. The primary efficacy outcome occurred in 32.1% (35/109) of patients who had been allocated TTP889, and 28.2% (29/103) of patients on placebo (P = 0.58). There were no major bleeding events, and only two clinically relevant non-major bleeding events with TTP889.

CONCLUSION

Partial FIXa inhibition with TTP889 300 mg daily was not effective for extended prevention of VTE after standard prophylaxis for up to 9 days. Coupled with the low incidence of bleeding episodes, this suggests a lack of antithrombotic potential. Further investigation of TTP889 in different clinical settings is needed. (Clinical trial registration information URL: http://www.clinicaltrials.gov. Unique identifier: NCT00119457).

Lower limb contrast venography: a modified technique for use in thromboprophylaxis clinical trials for the accurate evaluation of deep vein thrombosis

Lower limb venography remains the imaging modality of choice for detection of asymptomatic deep vein thrombosis (DVT) in clinical trials of anticoagulant agents. A variety of techniques of venography have been described. Here, we describe a modified technique (the "King's" technique) developed to increase the overall adequacy of identification of lower limb veins and detection of small asymptomatic DVT. Essential elements include proper preparation of patients prior to their arrival in the radiology department, intermittent use of tourniquets to ensure complete and adequate deep vein filling, use of a consistent image acquisition sequence and visualization of all veins in at least two different planes. Use of this technique minimizes technical difficulties, provides improved patient through-put in "busy" fluoroscopy units and, ultimately, improves "off-site" levels of adjudication.

Oral dabigatran etexilate vs. subcutaneous enoxaparin for the prevention of venous thromboembolism after total knee replacement: the RE-MODEL randomized trial

BACKGROUND

Oral anticoagulants, such as dabigatran etexilate, an oral, direct thrombin inhibitor, that do not require monitoring or dose adjustment offer potential for prophylaxis against venous thromboembolism (VTE) after total knee replacement surgery.

METHODS

In this randomized, double-blind study, 2076 patients undergoing total knee replacement received dabigatran etexilate, 150 mg or 220 mg once-daily, starting with a half-dose 1-4 hours after surgery, or subcutaneous enoxaparin 40 mg once-daily, starting the evening before surgery, for 6-10 days. Patients were followed-up for 3 months. The primary efficacy outcome was a composite of total VTE (venographic or symptomatic) and mortality during treatment, and the primary safety outcome was the incidence of bleeding events.

RESULTS

The primary efficacy outcome occurred in 37.7% (193 of 512) of the enoxaparin group versus 36.4% (183 of 503) of the dabigatran etexilate 220 mg group (absolute difference, -1.3%; 95% CI, -7.3 to 4.6) and 40.5% (213 of 526) of the 150 mg group (2.8%; 95% CI, -3.1 to 8.7). Both doses were noninferior to enoxaparin based on the pre-specified noninferiority criterion. The incidence of major bleeding did not differ significantly between the three groups (1.3% versus 1.5% and 1.3% respectively). No significant differences in the incidences of liver enzyme elevation and acute coronary events were observed during treatment or follow-up.

CONCLUSIONS

Dabigatran etexilate (220 mg or 150 mg) was at least as effective and with a similar safety profile as enoxaparin for prevention of VTE after total knee-replacement surgery.

Dabigatran etexilate versus enoxaparin for prevention of venous thromboembolism after total hip replacement: a randomised, double-blind, non-inferiority trial

BACKGROUND

After hip replacement surgery, prophylaxis following discharge from hospital is recommended to reduce the risk of venous thromboembolism. Our aim was to assess the oral, direct thrombin inhibitor dabigatran etexilate for such prophylaxis.

METHODS

In this double-blind study, we randomised 3494 patients undergoing total hip replacement to treatment for 28-35 days with dabigatran etexilate 220 mg (n=1157) or 150 mg (1174) once daily, starting with a half-dose 1-4 h after surgery, or subcutaneous enoxaparin 40 mg once daily (1162), starting the evening before surgery. The primary efficacy outcome was the composite of total venous thromboembolism (venographic or symptomatic) and death from all causes during treatment. On the basis of the absolute difference in rates of venous thromboembolism with enoxaparin versus placebo, the non-inferiority margin for the difference in rates of thromboembolism was defined as 7.7%. Efficacy analyses were done by modified intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00168818.

FINDINGS

Median treatment duration was 33 days. 880 patients in the dabigatran etexilate 220 mg group, 874 in the dabigatran etexilate 150 mg group, and 897 in the enoxaparin group were available for the primary efficacy outcome analysis; the main reasons for exclusion in all three groups were the lack of adequate venographic data. The primary efficacy outcome occurred in 60 (6.7%) of 897 individuals in the enoxaparin group versus 53 (6.0%) of 880 patients in the dabigatran etexilate 220 mg group (absolute difference -0.7%, 95% CI -2.9 to 1.6%) and 75 (8.6%) of 874 people in the 150 mg group (1.9%, -0.6 to 4.4%). Both doses were thus non-inferior to enoxaparin. There was no significant difference in major bleeding rates with either dose of dabigatran etexilate compared with enoxaparin (p=0.44 for 220 mg, p=0.60 for 150 mg). The frequency of increases in liver enzyme concentrations and of acute coronary events during the study did not differ significantly between the groups.

INTERPRETATION

Oral dabigatran etexilate was as effective as enoxaparin in reducing the risk of venous thromboembolism after total hip replacement surgery, with a similar safety profile.

A dose escalation study of YM150, an oral direct factor Xa inhibitor, in the prevention of venous thromboembolism in elective primary hip replacement surgery

BACKGROUND

YM150, a new oral direct factor Xa inhibitor is used as prophylaxis for venous thromboembolism (VTE), a well-known risk after orthopaedic surgery.

OBJECTIVES

To assess the safety and efficacy of thromboprophylaxis with YM150 in a dose escalation study.

PATIENTS/METHODS

Patients (174) undergoing hip replacement surgery were randomized per cohort to oral once daily YM150 or subcutaneous enoxaparin (40 mg daily) in a 4:1 ratio for 7-10 days treatment. The YM150 doses were 3, 10, 30 and 60 mg by sequential four-dose escalation cohorts. The primary endpoint was major and/or clinically relevant non-major bleeding. The incidence of VTE was defined as a composite of verified symptomatic events and/or positive findings at bilateral venography on the last treatment day. An independent adjudication committee evaluated blindly the outcomes of the open-label study.

RESULTS

No major and three clinically relevant non-major bleeds were reported, 1 (2.9%; 95% CI, 0.1-15.1) in the 3 mg and 2 (5.7%; 95% CI, 1.0-18.8) in the 10 mg YM150 dose groups. Of 147 patients (84%) with an evaluable venogram, VTE was observed in 51.9% (95% CI, 31.9-71.4), 38.7% (95% CI, 22.6-57.0), 22.6% (95% CI, 9.7-39.4), and 18.5% (95% CI, 7.5-36.5) in the YM150 dose groups 3, 10, 30 and 60 mg, respectively. A significant YM150 dose-related trend in VTE incidence was found (P=0.006). VTE with enoxaparin was 38.7% (95% CI, 22.6-57.0).

CONCLUSIONS

YM150, 10-60 mg daily, starting 6-10 h after primary hip replacement, was shown to be safe, well tolerated and effective.

Ultrasound screening for asymptomatic deep vein thrombosis after major orthopaedic surgery: the VENUS study

BACKGROUND

Venography is currently used to assess the incidence of deep vein thrombosis (DVT) in dose-finding and confirmatory trials of new antithrombotic agents. Centrally adjudicated, complete compression ultrasound (CCUS) could be a non-invasive alternative to venography.

OBJECTIVES

A substudy of two, similarly designed, phase IIb trials of a novel, oral anticoagulant for the prevention of venous thromboembolism after elective hip or knee arthroplasty was undertaken to validate CCUS against venography.

PATIENTS/METHODS

Patients received study drugs until mandatory, bilateral venography was performed 7 +/- 2 days after surgery. CCUS was performed within 24 h after venography by sonographers blinded to the venography result. Sonographers were trained and certified for the standardized examination and documentation procedure. Venograms and sonograms were adjudicated centrally at different sites by two independent readers; discrepancies between readers were resolved by consensus.

RESULTS

A total of 1104 matching pairs of evaluable venograms and sonograms were obtained from the participants of the two trials (n = 1435): 19% of venograms and 20% of sonograms were not evaluable. The observed frequency of any DVT was 18.9% with venography and 11.5% with CCUS. Sensitivity of CCUS compared with venography was 31.1% for any DVT (95% confidence interval 23.4, 38.9), 21.0% (2.7, 39.4) for proximal DVT, and 30.8% (23.1, 38.6) for distal DVT. The figures for specificity were 93.0% (91.0, 95.1), 98.7% (98.0, 99.5), and 93.3% (91.5, 95.3), respectively.

CONCLUSIONS

Based on these results, centrally adjudicated CCUS will be unable to replace venography for DVT screening early after major orthopaedic surgery in studies evaluating anticoagulant drugs.

Dose-escalation study of rivaroxaban (BAY 59-7939)--an oral, direct Factor Xa inhibitor--for the prevention of venous thromboembolism in patients undergoing total hip replacement

INTRODUCTION

Rivaroxaban (BAY 59-7939) is a novel, oral, direct Factor Xa inhibitor in clinical development for the prevention of thromboembolic disorders. The aim of this study was to demonstrate proof-of-principle for rivaroxaban.

MATERIALS AND METHODS

This was an open-label, dose-escalation study to assess the efficacy and safety of rivaroxaban, relative to enoxaparin, for the prevention of venous thromboembolism (VTE) after total hip replacement surgery. Patients were randomized in a 3:1 ratio to rivaroxaban (2.5, 5, 10, 20 and 30 mg twice daily [bid] or 30 mg once daily [od] starting 6-8 h after surgery) or enoxaparin (40 mg od starting the evening before surgery). Therapy continued until mandatory bilateral venography was performed 5-9 days after surgery.

RESULTS

A total of 625 patients received therapy, of whom 466 patients were eligible for the per-protocol efficacy analysis. The primary efficacy endpoint - deep vein thrombosis (DVT), pulmonary embolism (PE) or all-cause mortality - occurred in 22.2%, 23.8%, 20.0%, 10.2%, 17.4%, 15.1% and 16.8% of patients receiving rivaroxaban 2.5, 5, 10, 20, 30 mg bid, 30 mg od and enoxaparin, respectively. The dose-response relationship with rivaroxaban for the primary efficacy endpoint was not statistically significant (p=0.0504), although major VTE (proximal DVT, PE and VTE-related death) decreased dose dependently with rivaroxaban (p=0.0108). Major, post-operative bleeding increased dose dependently with rivaroxaban (p=0.0008), occurring in 0-10.8% of patients, compared with 0% in patients receiving enoxaparin.

CONCLUSIONS

This study demonstrated proof-of-principle for rivaroxaban for the prevention of VTE after total hip replacement surgery.

A once-daily, oral, direct Factor Xa inhibitor, rivaroxaban (BAY 59-7939), for thromboprophylaxis after total hip replacement

BACKGROUND

Rivaroxaban (BAY 59-7939)--an oral, direct Factor Xa inhibitor--could be an alternative to heparins and warfarin for the prevention and treatment of thromboembolic disorders.

METHODS AND RESULTS

This randomized, double-blind, double-dummy, active-comparator-controlled, multinational, dose-ranging study assessed the efficacy and safety of once-daily rivaroxaban relative to enoxaparin for prevention of venous thromboembolism in patients undergoing elective total hip replacement. Patients (n=873) were randomized to once-daily oral rivaroxaban doses of 5, 10, 20, 30, or 40 mg (initiated 6 to 8 hours after surgery) or a once-daily subcutaneous enoxaparin dose of 40 mg (given the evening before and > or = 6 hours after surgery). Study drugs were continued for an additional 5 to 9 days; mandatory bilateral venography was performed the following day. The primary end point (composite of any deep vein thrombosis, objectively confirmed pulmonary embolism, and all-cause mortality) was observed in 14.9%, 10.6%, 8.5%, 13.5%, 6.4%, and 25.2% of patients receiving 5, 10, 20, 30, and 40 mg rivaroxaban, and 40 mg enoxaparin, respectively (n=618, per-protocol population). No significant dose-response relationship was found for efficacy (P=0.0852). Major postoperative bleeding was observed in 2.3%, 0.7%, 4.3%, 4.9%, 5.1%, and 1.9% of patients receiving 5, 10, 20, 30, and 40 mg rivaroxaban, and 40 mg enoxaparin, respectively (n=845, safety population), representing a significant dose-response relationship (P=0.0391).

CONCLUSIONS

Rivaroxaban showed efficacy and safety similar to enoxaparin for thromboprophylaxis after total hip replacement, with the convenience of once-daily oral dosing and without the need for coagulation monitoring. When both efficacy and safety are considered, these results suggest that 10 mg rivaroxaban once daily should be investigated in phase III studies.

Oral Anticoagulants in Development

Current anticoagulant provision is dominated by parenteral heparin and oral warfarin, which act by inhibiting several steps of the coagulation pathway indirectly. Recent research efforts have focused on the identification of small molecule inhibitors of the coagulation enzymes as novel therapies for thrombotic disorders. There has been particular success in developing nonpeptidic, orally available, small molecules to directly inhibit the key proteases, factor IIa and factor Xa. Of the new oral anticoagulants in development, the two agents in the most advanced stage are dabigatran etexilate (BIBR 1048) and rivaroxaban (BAY 59-7939), which inhibit factor IIa and factor Xa, respectively. Other agents in the early stages of development include several Xa inhibitors (LY-517717, YM150, DU-176b and apixaban [BMS-562247]), a factor IXa inhibitor (TTP889), and an orally active glycosaminoglycan enhancer (odiparcil [SB-424323]), which indirectly enhances thrombin inhibition via heparin cofactor II. Results have been reported from important, phase II dose-finding studies, and a number of registration-track phase III studies have been initiated, reflecting the drive towards potentially more effective, but primarily safer and more convenient therapies for the prevention and treatment of venous and arterial thrombosis. Indeed, two unmet needs for anticoagulation that can be easily identified are safety and ease of use. Safety relates primarily to the incidence of major bleeding and this remains the key concern of orthopaedic surgeons, over and above any efficacy advantage, and convenience of use, which centres on oral administration replacing the need for injections. The clinical development of these new anticoagulants is following the well tested strategy of dose-ranging and registration studies in major orthopaedic surgery, prior to development in arterial indications. There are a number of subtle issues, including the timing of the first perioperative dose, duration of prophylactic treatment and definition/assessment of study endpoints that can influence study outcome and require careful consideration when evaluating study results with new agents and in the comparison with established agents, and which are considered in this review. It is anticipated that over the next 3 years, at least one of these agents will be successfully licensed for the prevention of venous thromboembolism after major orthopaedic surgery, which will act as a springboard for the gradual replacement of current anticoagulants.

Oral, direct Factor Xa inhibition with BAY 59-7939 for the prevention of venous thromboembolism after total hip replacement

BACKGROUND

Joint replacement surgery is an appropriate model for dose-ranging studies investigating new anticoagulants.

OBJECTIVES

To assess the efficacy and safety of a novel, oral, direct factor Xa (FXa) inhibitor--BAY 59-7939--relative to enoxaparin in patients undergoing elective total hip replacement.

METHODS

In this double-blind, double-dummy, dose-ranging study, patients were randomized to oral BAY 59-7939 (2.5, 5, 10, 20, or 30 mg b.i.d.), starting 6-8 h after surgery, or s.c. enoxaparin 40 mg once daily, starting on the evening before surgery. Treatment was continued until mandatory bilateral venography was performed 5-9 days after surgery.

RESULTS

Of 706 patients treated, 548 were eligible for the primary efficacy analysis. The primary efficacy endpoint was the incidence of any deep vein thrombosis, non-fatal pulmonary embolism, and all-cause mortality; rates were 15%, 14%, 12%, 18%, and 7% for BAY 59-7939 2.5, 5, 10, 20, and 30 mg b.i.d., respectively, compared with 17% for enoxaparin. The primary efficacy analysis did not demonstrate any significant trend in dose-response relationship for BAY 59-7939. The primary safety endpoint was major, postoperative bleeding; there was a significant increase in the frequency of events with increasing doses of BAY 59-7939 (P = 0.045), but no significant differences between individual BAY 59-7939 doses and enoxaparin.

CONCLUSIONS

When efficacy and safety were considered together, the oral, direct FXa inhibitor BAY 59-7939, at 2.5-10 mg b.i.d., compared favorably with enoxaparin for the prevention of venous thromboembolism in patients undergoing elective total hip replacement.

BAY 59-7939: an oral, direct factor Xa inhibitor for the prevention of venous thromboembolism in patients after total knee replacement. A phase II dose-ranging study

BACKGROUND

BAY 59-7939, a novel, oral, direct factor Xa inhibitor, is in clinical development for the prevention of venous thromboembolism (VTE), a frequent complication following orthopaedic surgery.

METHODS

In a multicenter, parallel-group, double-blind, double-dummy study, 621 patients undergoing elective total knee replacement were randomly assigned to oral BAY 59-7939 (2.5, 5, 10, 20, and 30 mg b.i.d., initiated 6-8 h postsurgery), or subcutaneous enoxaparin (30 mg b.i.d., initiated 12-24 h postsurgery). Treatment was continued until mandatory bilateral venography 5-9 days after surgery. The primary efficacy endpoint was a composite of any deep vein thrombosis (proximal and/or distal), confirmed non-fatal pulmonary embolism and all-cause mortality during treatment. The primary safety endpoint was major, postoperative bleeding during treatment.

RESULTS

Of the 613 patients treated, 366 (59.7%) were evaluable for the primary efficacy analysis. The primary efficacy endpoint occurred in 31.7%, 40.4%, 23.3%, 35.1%, and 25.4% of patients receiving 2.5, 5, 10, 20 and 30 mg b.i.d. doses of BAY 59-7939, respectively (test for trend, P = 0.29), compared with 44.3% in the enoxaparin group. The frequency of major, postoperative bleeding increased with increasing doses of BAY 59-7939 (test for trend, P = 0.0007), with no significant difference between any dose group compared with enoxaparin. Bleeding endpoints were lower for the 2.5-10 mg b.i.d. doses compared with higher doses of BAY 59-7939.

CONCLUSIONS

Oral administration of 2.5-10 mg b.i.d. of BAY 59-7939, early in the postoperative period, showed potential efficacy and an acceptable safety profile, similar to enoxaparin, for the prevention of VTE in patients undergoing elective total knee replacement.

Methodological issues in trials assessing primary prophylaxis of venous thrombo-embolism

AIMS

Many trials have been conducted to assess the efficacy of various strategies in the prevention of venous thrombo-embolism (VTE). Some of these trials have been subject to methodological criticisms. We aimed to assess the methodological issues raised by VTE trials.

METHODS AND RESULTS

We searched MEDLINE and the Cochrane Central Register of Controlled Trials for articles assessing primary thromboprophylaxis published between 1994 and 2003 in 60 general medical and specialty journals. A total of 77 articles were analysed by two independent reviewers using a list of items. No primary endpoint was defined in 20% of trials. Although the primary endpoint was collected before day 15 in 75% of trials, there were >/=20% missing data in 56% of articles and >/=30% in 24.2% of articles. The rate of missing data was 23.7+/-9.7% in studies using venography-detected deep-vein thrombosis as an endpoint compared with 5.6+/-6.0% in studies using other endpoints. Among the 47 superiority trials, 27 (57.4%) reported an intention-to-treat (ITT) analysis, but only 10 (21.3%) reported an analysis that complied with this principle. These results were consistent when limiting the analysis to articles published in high-impact journal (impact factor more than 5).

CONCLUSION

Recent randomized controlled trials assessing prophylactic regimens in VTE have important methodological limitations in terms of primary endpoints, missing data, and compliance with the ITT principle. These methodological shortcomings should be addressed when planning future trials.

A new oral direct thrombin inhibitor, dabigatran etexilate, compared with enoxaparin for prevention of thromboembolic events following total hip or knee replacement: the BISTRO II randomized trial

BACKGROUND

Dabigatran etexilate is an oral direct thrombin inhibitor undergoing evaluation for the prevention of venous thromboembolism (VTE) following orthopedic surgery.

METHODS

In a multicenter, parallel-group, double-blind study, 1973 patients undergoing total hip or knee replacement were randomized to 6-10 days of oral dabigatran etexilate (50, 150 mg twice daily, 300 mg once daily, 225 mg twice daily), starting 1-4 h after surgery, or subcutaneous enoxaparin (40 mg once daily) starting 12 h prior to surgery. The primary efficacy outcome was the incidence of VTE (detected by bilateral venography or symptomatic events) during treatment.

RESULTS

Of the 1949 treated patients, 1464 (75%) patients were evaluable for the efficacy analysis. VTE occurred in 28.5%, 17.4%, 16.6%, 13.1% and 24% of patients assigned to dabigatran etexilate 50, 150 mg twice daily, 300 mg once daily, 225 mg twice daily and enoxaparin, respectively. A significant dose-dependent decrease in VTE occurred with increasing doses of dabigatran etexilate (P < 0.0001). Compared with enoxaparin, VTE was significantly lower in patients receiving 150 mg twice daily [odds ratio (OR) 0.65, P = 0.04], 300 mg once daily (OR 0.61, P = 0.02) and 225 mg twice daily (OR 0.47, P = 0.0007). Compared with enoxaparin, major bleeding was significantly lower with 50 mg twice daily (0.3% vs. 2.0%, P = 0.047) but elevated with higher doses, nearly reaching statistical significance with the 300 mg once-daily dose (4.7%, P = 0.051).

CONCLUSIONS

Oral administration of dabigatran etexilate, commenced early in the postoperative period, was effective and safe across a range of doses. Further optimization of the efficacy/safety balance will be addressed in future studies.

Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

This article discusses the prevention of venous thromboembolism (VTE) and is part of the Seventh American College of Chest Physicians 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. We recommend against the use of aspirin alone as thromboprophylaxis for any patient group (Grade 1A). For moderate-risk general surgery patients, we recommend prophylaxis with low-dose unfractionated heparin (LDUH) (5,000 U bid) or low-molecular-weight heparin (LMWH) [< or = 3,400 U once daily] (both Grade 1A). For higher risk general surgery patients, we recommend thromboprophylaxis with LDUH (5,000 U tid) or LMWH (> 3,400 U daily) [both Grade 1A]. For high-risk general surgery patients with multiple risk factors, we recommend combining pharmacologic methods (LDUH three times daily or LMWH, > 3,400 U daily) with the use of graduated compression stockings and/or intermittent pneumatic compression devices (Grade 1C+). We recommend that thromboprophylaxis be used in all patients undergoing major gynecologic surgery (Grade 1A) or major, open urologic procedures, and we recommend prophylaxis with LDUH two times or three times daily (Grade 1A). For patients undergoing elective total hip or knee arthroplasty, we recommend one of the following three anticoagulant agents: LMWH, fondaparinux, or adjusted-dose vitamin K antagonist (VKA) [international normalized ratio (INR) target, 2.5; range, 2.0 to 3.0] (all Grade 1A). For patients undergoing hip fracture surgery (HFS), we recommend the routine use of fondaparinux (Grade 1A), LMWH (Grade 1C+), VKA (target INR, 2.5; range, 2.0 to 3.0) [Grade 2B], or LDUH (Grade 1B). We recommend that patients undergoing hip or knee arthroplasty, or HFS receive thromboprophylaxis for at least 10 days (Grade 1A). We recommend that all trauma patients with at least one risk factor for VTE receive thromboprophylaxis (Grade 1A). In acutely ill medical patients who have been admitted to the hospital with congestive heart failure or severe respiratory disease, or who are confined to bed and have one or more additional risk factors, we recommend prophylaxis with LDUH (Grade 1A) or LMWH (Grade 1A). We recommend, on admission to the intensive care unit, all patients be assessed for their risk of VTE. Accordingly, most patients should receive thromboprophylaxis (Grade 1A).

Dose escalating safety study of a new oral direct thrombin inhibitor, dabigatran etexilate, in patients undergoing total hip replacement: BISTRO I

BACKGROUND

Dabigatran etexilate (BIBR 1048) is an oral direct thrombin inhibitor undergoing evaluation for the prevention of venous thromboembolism (VTE) following total hip replacement. Following oral administration, dabigatran etexilate is rapidly converted to its active form dabigatran (BIBR 953 ZW).

OBJECTIVES

To determine the safe therapeutic range of dabigatran etexilate following total hip replacement.

METHODS

In a multicenter, open-label, dose-escalating study, 314 patients received oral doses of dabigatran etexilate (12.5, 25, 50, 100, 150, 200 and 300 mg twice daily or 150 and 300 mg once daily) administered 4-8 h after surgery, for 6-10 days. Dose escalation was based on clinical and pharmacokinetic data. The primary safety outcome was major bleeding. The primary efficacy outcome included venographic deep vein thrombosis (DVT), symptomatic DVT and pulmonary embolism, during the treatment period.

RESULTS

No major bleeding event was observed in any group, but two patients at the highest dose (300 mg twice daily) suffered bleeding from multiple sites associated with reduced renal clearance and prolonged pharmacodynamic (PD) parameters. A dose-response was demonstrated for minor bleeding events. Of the 289 treated patients, 225 patients had evaluable venograms. The overall incidence of DVT was 12.4% (28/225 patients). There was no consistent relationship between the dose and incidence of DVT, the highest incidence in any group being 20.8% (5/24 patients). The lowest dose (12.5 mg twice daily) showed a high rate of proximal DVT [12.5% (3/24)] and no increase in PD parameters. Peak and trough plasma concentrations, area under the dabigatran plasma concentration-time curve and PD parameters also increased in proportion with the dose. Higher dabigatran plasma concentrations were associated with lower DVT rates. Approximately 20% of the patients had low plasma concentrations after the first dose suggesting further optimization of the preliminary tablet formulation is required.

CONCLUSIONS

Dabigatran etexilate demonstrates an acceptable safety profile, with a therapeutic window above 12.5 mg and below 300 mg twice daily. The low number of VTE events within each treatment group indicates a satisfactory antithrombotic potential, although the study was not powered for an efficacy analysis. Additional studies are ongoing to optimize oral absorption and the efficacy/safety balance.

The direct thrombin inhibitor melagatran followed by oral ximelagatran compared with enoxaparin for the prevention of venous thromboembolism after total hip or knee replacement: the EXPRESS study

BACKGROUND

Ximelagatran and its subcutaneous (s.c.) form melagatran are novel direct thrombin inhibitors for the prevention and treatment of thromboembolic disease.

METHODS

In a double-blind study, 2835 consecutive patients undergoing total hip or knee replacement were randomized to either melagatran/ximelagatran or enoxaparin. Melagatran 2 mg was started immediately before surgery; 3 mg was then administered postoperatively, followed by 24 mg of oral ximelagatran b.i.d. beginning the next day. Enoxaparin 40 mg, administered subcutaneously o.d., was started 12 h before surgery. Both treatments were continued for 8-11 days. The main efficacy outcome measures were major venous thromboembolism (VTE); [proximal deep vein thrombosis (DVT), non-fatal and/or fatal pulmonary embolism (PE), death where PE could not be ruled out], and total VTE (proximal and distal DVT; PE; death from all causes). DVT was detected by mandatory bilateral ascending venography at the end of the treatment period or earlier if clinically suspected. The main safety outcome was bleeding.

RESULTS

The rates of major and total VTE were significantly lower in the melagatran/ximelagatran group compared with the enoxaparin group (2.3% vs. 6.3%, P = 0.0000018; and 20.3% vs. 26.6%, P < 0.0004, respectively). Fatal bleeding, critical site bleeding and bleeding requiring reoperation did not differ between the two groups. 'Excessive bleeding as judged by the investigator' was more frequent with melagatran/ximelagatran than with enoxaparin.

CONCLUSIONS

In patients undergoing total hip or knee replacement, preoperatively initiated s.c. melagatran followed by oral ximelagatran was significantly more effective in preventing VTE than preoperatively initiated s.c. enoxaparin.

Comparison of ximelagatran with warfarin for the prevention of venous thromboembolism after total knee replacement

BACKGROUND

In a previous study of the prevention of venous thromboembolism after total knee replacement, the efficacy of ximelagatran, an oral direct thrombin inhibitor that does not require monitoring of coagulation or dose adjustment, was found to be similar to that of warfarin at a dose of 24 mg of ximelagatran twice daily. The purpose of the present study was to determine whether a higher dose of ximelagatran is superior to warfarin.

METHODS

This randomized, double-blind trial compared a regimen of 7 to 12 days of oral ximelagatran, at a dose of 24 or 36 mg twice daily, starting the morning after surgery, with warfarin therapy started the evening of the day of surgery. The composite end point of venous thromboembolism and death from all causes and the incidence of bleeding were the primary outcome measures.

RESULTS

Among the 1851 patients in the efficacy analysis, oral ximelagatran at a dose of 36 mg twice daily was superior to warfarin with respect to the primary composite end point of venous thromboembolism and death from all causes (20.3 percent vs. 27.6 percent; P=0.003). There were no significant differences between these two groups with respect to major bleeding (incidence, 0.8 percent and 0.7 percent, respectively), perioperative indicators of bleeding, wound characteristics, or the composite secondary end point of proximal deep-vein thrombosis, pulmonary embolism, and death (2.7 percent vs. 4.1 percent; P=0.17).

CONCLUSIONS

The efficacy of oral ximelagatran, administered starting the morning after total knee replacement, was superior to that of warfarin for prevention of venous thromboembolism. Rates of hemorrhagic complications with the two drugs were similar.

Comparison of ximelagatran, an oral direct thrombin inhibitor, with enoxaparin for the prevention of venous thromboembolism following total hip replacement. A randomized, double-blind study

BACKGROUND

Prophylaxis is recommended following total joint replacement because of the high risk of venous thromboembolism (VTE). Postoperative low-molecular-weight heparin (LMWH) reduces the incidence of venographically detected deep vein thrombosis (DVT) to about 10-15% in total hip replacement (THR) patients. Ximelagatran is a novel, oral direct thrombin inhibitor that selectively and competitively inhibits both free and clot-bound thrombin. We compared the efficacy and safety of ximelagatran with those of enoxaparin for the prevention of VTE in patients undergoing THR.

METHODS

This was a prospective, randomized, multicenter, double-blind study conducted principally in the USA and Canada. Patients received fixed-dose oral ximelagatran 24 mg bid or subcutaneous enoxaparin 30 mg bid and matched placebo for 7-12 days; both regimens were initiated the morning after surgery. The incidence of VTE (by postoperative day 12) included thrombosis determined by mandatory venography of the leg on which surgery was performed and symptomatic, objectively proven DVT or pulmonary embolism (PE). VTE and bleeding events were interpreted by an independent central adjudication committee for primary analysis.

RESULTS

Of the 1838 patients randomized, 1557 had either adequate venography or symptomatic, proven VTE (efficacy population). Overall rate of venography acceptable for evaluation was 85.4%. Overall rates of total VTE were 7.9% (62 of 782 patients) in the ximelagatran group and 4.6% (36 of 775 patients) in the enoxaparin group, with an absolute difference of 3.3% and a 95% confidence interval for the difference of 0.9% to 5.7%. Proximal DVT and/or PE occurred in 3.6% (28 of 782 patients) in the ximelagatran group and 1.2% (nine of 774 patients) in the enoxaparin group. Major bleeding events were observed in 0.8% (seven of 906) of the ximelagatran-treated patients and in 0.9% (eight of 910) of the enoxaparin-treated patients (P > 0.95). Non-inferiority of ximelagatran 24 mg bid based on a prespecified margin of 5% was not met, resulting in superiority of the enoxaparin regimen.

CONCLUSIONS

Both ximelagatran and enoxaparin decreased the overall rate of VTE compared with that reported historically. However, in this study, enoxaparin 30 mg bid was more effective than ximelagatran 24 mg bid for prevention of VTE in THR. Oral ximelagatran was used without coagulation monitoring, was well tolerated, and had bleeding rates comparable to those of enoxaparin. Further refinement by testing a higher dose of ximelagatran in the patients undergoing THR is warranted.

Ximelagatran and melagatran compared with dalteparin for prevention of venous thromboembolism after total hip or knee replacement: the METHRO II randomised trial

BACKGROUND

Heparins substantially reduce the risk of thromboembolic complications after total hip or knee replacement. However, they can be given only by injection and have several other drawbacks. We did a multicentre, randomised, double-blind study to examine the dose-response relation of subcutaneous melagatran, a direct thrombin inhibitor, followed by oral ximelagatran as thromboprophylaxis after total hip or knee replacement. We aimed to compare the efficacy and safety with that of dalteparin.

METHODS

Of 1900 patients, 1495 were assigned to four dose categories of subcutaneous melagatran from just before surgery (1.00 mg, 1.50 mg, 2.25 mg, or 3.00 mg twice daily) followed from the day after surgery by oral ximelagatran (8 mg, 12 mg, 18 mg, or 24 mg twice daily). 381 patients were assigned subcutaneous dalteparin 5000 IU once daily, from the evening before surgery. Bilateral venography was done at 7-10 days, and clinically suspected venous thromboembolism (VTE) was confirmed radiologically. The primary endpoint was the rate of deep-vein thrombosis and pulmonary embolism (PE). Analyses were by intention to treat.

FINDINGS

1876 patients underwent total replacement of hip (n=1270) or knee (n=606); evaluable venograms were obtained in 1473 (79%). Four patients without evaluable venograms had PE. Overall, a significant dose-dependent decrease in VTE was seen with melagatran/ximelagatran (lowest to highest group: 111 [37.8%], 70 [24.1%], 71 [23.7%], and 43 [15.1%]; p=0.0001); there were also significant relations for both total hip and total knee replacement individually. The frequency of VTE was significantly lower with the highest dose of melagatran/ximelagatran than with dalteparin (15.1% vs 28.2%, p<0.0001). There were no reoperations due to bleeding and no critical organ bleeding. Excessive surgical bleeding was uncommon but more frequent in the highest dose group.

INTERPRETATION

This sequential therapy was effective and safe in patients undergoing major joint replacement surgery. The findings should be confirmed in a large phase III trial.

Prophylaxis of venous thromboembolism with subcutaneous melagatran in total hip or total knee replacement: results from Phase II studies

The first clinical studies evaluating the safety and efficacy of melagatran, a novel, direct thrombin inhibitor, given subcutaneously as prophylaxis for venous thromboembolism (VTE) following total hip (THR) or total knee replacement (TKR) are reported. In Study I, 66 patients received subcutaneous melagatran (1.5-6 mg bid) in a poloxamer depot formulation, and in Study II, 104 patients received subcutaneous melagatran (2-4 mg bid) in saline or as a depot formulation in cyclodextrin. Treatment was given for 8-11 days, with the first dose administered immediately before surgery. Deep vein thrombosis (DVT) was assessed using mandatory bilateral venography on the last day of treatment, and pulmonary scintigraphy was performed if required. Bleeding complications occurred in the only patient who received melagatran 6 mg, and this dose-arm was discontinued. The frequency of VTE was low (12/129=9%, 95% confidence interval [CI]: 5-16%). Eight patients (6%) had distal DVT, three (2%) had proximal DVT, and in one patient (1%) pulmonary embolism (PE) was verified. In conclusion, subcutaneous melagatran 1.5-4.5 mg bid in saline or depot formulation was well tolerated and resulted in a low frequency of VTE.

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.