Publications by authors named "Mark Blostein"

49 Publications

Cost-effectiveness of eltrombopag versus intravenous immunoglobulin for the perioperative management of immune thrombocytopenia.

Blood Adv 2021 Nov 15. Epub 2021 Nov 15.

McMaster University, Hamilton, Canada.

Eltrombopag has been shown to be non-inferior to intravenous immunoglobulin (IVIG) for improving perioperative platelet counts in patients with immune thrombocytopenia (ITP) in a randomized trial; thus, cost is an important factor for treatment and policy decisions. We used patient-level data from the trial to conduct a cost-effectiveness analysis comparing perioperative eltrombopag 50mg daily starting dose, with IVIG 1 or 2g/kg (according to local practice) from a Canadian public healthcare payer's perspective over the observation period, from preoperative day 21 to postoperative day 28. Resource utilization data were obtained from the trial data (eltrombopag, n=38; IVIG, n=36) and unit costs were collected from the Ontario Schedule of Benefits, Ontario Drug Formulary, and secondary sources. All costs were adjusted to 2020 Canadian dollars. We calculated the incremental cost per patient for all patients randomized. Uncertainty was addressed using non-parametric bootstrapping. The use of perioperative eltrombopag for patients with ITP resulted in a cost-saving of $413 Canadian dollars per patient. Compared with IVIG, the probability of eltrombopag being cost-effective was 70% even with zero willingness to pay. In a sensitivity analysis based on IVIG dose, we found that with the higher dose of IVIG (2g/kg), eltrombopag saved $2,714 per patient; whereas with the lower dose of IVIG (1g/kg), eltrombopag had a higher mean cost of $562 per patient. In summary, based on data from the randomized trial that demonstrated non-inferiority, the use of eltrombopag for the management of ITP in the perioperative setting was less costly than IVIG.
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http://dx.doi.org/10.1182/bloodadvances.2021005627DOI Listing
November 2021

Postoperative low molecular weight heparin bridging treatment for patients at high risk of arterial thromboembolism (PERIOP2): double blind randomised controlled trial.

BMJ 2021 06 9;373:n1205. Epub 2021 Jun 9.

Department of Medicine, McGill University, Montreal, QC, Canada.

Objective: To determine the efficacy and safety of dalteparin postoperative bridging treatment versus placebo for patients with atrial fibrillation or mechanical heart valves when warfarin is temporarily interrupted for a planned procedure.

Design: Prospective, double blind, randomised controlled trial.

Setting: 10 thrombosis research sites in Canada and India between February 2007 and March 2016.

Participants: 1471 patients aged 18 years or older with atrial fibrillation or mechanical heart valves who required temporary interruption of warfarin for a procedure.

Intervention: Random assignment to dalteparin (n=821; one patient withdrew consent immediately after randomisation) or placebo (n=650) after the procedure.

Main Outcome Measures: Major thromboembolism (stroke, transient ischaemic attack, proximal deep vein thrombosis, pulmonary embolism, myocardial infarction, peripheral embolism, or vascular death) and major bleeding according to the International Society on Thrombosis and Haemostasis criteria within 90 days of the procedure.

Results: The rate of major thromboembolism within 90 days was 1.2% (eight events in 650 patients) for placebo and 1.0% (eight events in 820 patients) for dalteparin (P=0.64, risk difference -0.3%, 95% confidence interval -1.3 to 0.8). The rate of major bleeding was 2.0% (13 events in 650 patients) for placebo and 1.3% (11 events in 820 patients) for dalteparin (P=0.32, risk difference -0.7, 95% confidence interval -2.0 to 0.7). The results were consistent for the atrial fibrillation and mechanical heart valves groups.

Conclusions: In patients with atrial fibrillation or mechanical heart valves who had warfarin interrupted for a procedure, no significant benefit was found for postoperative dalteparin bridging to prevent major thromboembolism.

Trial Registration: Clinicaltrials.gov NCT00432796.
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http://dx.doi.org/10.1136/bmj.n1205DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8188228PMC
June 2021

Performance of two clinical scales to assess quality of life in patients with post-thrombotic syndrome.

J Vasc Surg Venous Lymphat Disord 2021 09 4;9(5):1257-1265.e2. Epub 2021 Feb 4.

Department of Medicine, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada; Lady Davis Institute, Jewish General Hospital, Montreal, Quebec, Canada.

Objective: We directly compared the Villalta scale and the Venous Clinical Severity Score (VCSS) to determine which of the two measures would be better at capturing clinically important cases of post-thrombotic syndrome (PTS) and PTS severity compared with patient-reported quality of life (QOL) scores.

Methods: We performed a secondary analysis of the ATTRACT (acute venous thrombosis: thrombus removal with adjunctive catheter-directed thrombolysis) trial study population. We calculated the correlations of the Villalta scores and VCSSs with QOL scores (short-form 36-item health survey [SF-36] physical component summary [PCS] and mental component summary [MCS]; and VEINES [venous insufficiency epidemiological and economic study]-QOL/symptom [VEINES-QOL/Sym] questionnaire) at each study visit (6, 12, 18, and 24 months of follow-up). The correlation of the random intercept (mean scores) and random slope (rate of change of the scores) among the Villalta scores, VCSS, and VEINES-QOL/Sym scores was assessed using a multivariate longitudinal model.

Results: The median correlation between Villalta scores and VCSSs was 0.72. The median correlation between the Villalta scores and VEINES-QOL and VEINES-Sym scores at all follow-up visits was -0.68 and -0.71, respectively. The median correlation between the Villalta scores and SF-36 PCS and MCS scores was -0.51 and -0.31, respectively. For the VCSSs, the median correlation with the VEINES-QOL and VEINES-Sym scores at all follow-up visits was -0.39 and -0.41, respectively. The median correlation between the VCSSs and SF-36 PCS and MCS scores was -0.32 and -0.13, respectively. The correlations between the random effects in the multivariate longitudinal models showed a similar pattern. The effect of covariate adjustment by age, sex, and body mass index was minor.

Conclusions: The Villalta scores and VCSSs correlated strongly. The Villalta scale showed a substantially greater correlation with venous disease-specific and general QOL scores compared with the correlation with the VCSS. Our findings suggest that when a single scale is used to assess for clinically meaningful PTS, the Villalta scale will better capture the effects of PTS on patient-reported QOL.
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http://dx.doi.org/10.1016/j.jvsv.2021.01.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8333181PMC
September 2021

Muscle Mass and Direct Oral Anticoagulant Activity in Older Adults With Atrial Fibrillation.

J Am Geriatr Soc 2021 04 11;69(4):1012-1018. Epub 2021 Jan 11.

Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada.

Background: Direct oral anticoagulants (DOAC) are hydrophilic drugs with plasma levels inversely proportional to lean body mass. Sarcopenic patients with low muscle mass may be at risk for supra-therapeutic DOAC levels and bleeding complications. We therefore sought to examine the influence of lean body mass on DOAC levels in older adults with atrial fibrillation (AF).

Methods: A prospective cohort study was conducted with patients 65 years of age or more receiving rivaroxaban or apixaban for AF. Appendicular lean mass (ALM) was measured using a bioimpedance device and a dual X-ray absorptiometry scanner. DOAC levels were measured using a standardized anti-Xa assay 4 hours after (peak) and 1 hour before (trough) ingestion.

Results: The cohort consisted of 62 patients (47% female, 77.0 ± 6.1 years). The prescribed DOACs were apixaban 2.5 mg (21%), apixaban 5 mg (53%), and rivaroxaban 20 mg (26%). Overall, 16% had supra-therapeutic DOAC levels at trough and 25% at peak. In the multivariable logistic regression model, lower ALM was independently associated with supra-therapeutic DOAC levels at trough (odds ratio per ↓ 1-kg 1.23, 95% confidence interval 1.02 to 1.49) and peak (odds ratio per ↓ 1-kg 1.18, 95% confidence interval 1.02 to 1.37). Addition of ALM to a model consisting of age, total body weight, and renal function resulted in improved discrimination for supra-therapeutic DOAC levels.

Conclusion: Our proof-of-concept study has identified an association between ALM and DOAC levels in older adults with AF. Further research is needed to determine the impact of ALM on bleeding complications and the potential role of ALM-guided dosing for sarcopenic patients.
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http://dx.doi.org/10.1111/jgs.16992DOI Listing
April 2021

Perioperative oral eltrombopag versus intravenous immunoglobulin in patients with immune thrombocytopenia: a non-inferiority, multicentre, randomised trial.

Lancet Haematol 2020 Sep;7(9):e640-e648

Michael G DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada; McMaster Centre for Transfusion Research, Department of Medicine, McMaster University, Hamilton, ON, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.

Background: Patients with immune thrombocytopenia are at risk of bleeding during surgery, and intravenous immunoglobulin is commonly used to increase the platelet count. We aimed to establish whether perioperative eltrombopag was non-inferior to intravenous immunoglobulin.

Methods: We did a randomised, open-label trial in eight academic hospitals in Canada. Patients were aged at least 18 years, with primary or secondary immune thrombocytopenia and platelet counts less than 100 × 10 cells per L before major surgery or less than 50 × 10 cells per L before minor surgery. Previous intravenous immunoglobulin within 2 weeks or thrombopoietin receptor agonists within 4 weeks before randomisation were not permitted. Patients were randomly assigned to receive oral daily eltrombopag 50 mg from 21 days preoperatively to postoperative day 7 or intravenous immunoglobulin 1 g/kg or 2 g/kg 7 days before surgery. Eltrombopag dose adjustments were allowed weekly based on platelet counts. The randomisation sequence was generated by a computerised random number generator, concealed and stratified by centre and surgery type (major or minor). The central study statistician was masked to treatment allocation. The primary outcome was achievement of perioperative platelet count targets (90 × 10 cells per L before major surgery or 45 × 10 cells per L before minor surgery) without rescue treatment. We did intention-to-treat and per-protocol analyses using an absolute non-inferiority margin of -10%. This trial is registered with ClinicalTrials.gov, NCT01621204.

Findings: Between June 5, 2013, and March 7, 2019, 92 patients with immune thrombocytopenia were screened, of whom 74 (80%) were randomly assigned: 38 to eltrombopag and 36 to intravenous immunoglobulin. Median follow-up was 50 days (IQR 49-55). By intention-to-treat analysis, perioperative platelet targets were achieved for 30 (79%) of 38 patients assigned to eltrombopag and 22 (61%) of 36 patients assigned to intravenous immunoglobulin (absolute risk difference 17·8%, one-sided lower limit of the 95% CI 0·4%; p=0·005). In the per-protocol analysis, perioperative platelet targets were achieved for 29 (78%) of 37 patients in the eltrombopag group and 20 (63%) of 32 in the intravenous immunoglobulin group (absolute risk difference 15·9%, one-sided lower limit of the 95% CI -2·1%; p=0·009). Two serious adverse events occurred in the eltrombopag group: one treatment-related pulmonary embolism and one vertigo. Five serious adverse events occurred in the intravenous immunoglobulin group (atrial fibrillation, pancreatitis, vulvar pain, chest tube malfunction and conversion to open splenectomy); all were related to complications of surgery. No treatment-related deaths occurred.

Interpretation: Eltrombopag is an effective alternative to intravenous immunoglobulin for perioperative treatment of immune thrombocytopenia. However, treatment with eltrombopag might increase risk of thrombosis. The decision to choose one treatment over the other will depend on patient preference, resource limitations, cost, and individual risk profiles.

Funding: GlaxoSmithKline and Novartis.
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http://dx.doi.org/10.1016/S2352-3026(20)30227-1DOI Listing
September 2020

Correction to: A single-arm feasibility cohort study of rivaroxaban in antiphospholipid syndrome.

Pilot Feasibility Stud 2020 18;6:67. Epub 2020 May 18.

1Department of Medicine, McMaster University, 1280 Main St. W, Hamilton, ON L8S 4L8 Canada.

[This corrects the article DOI: 10.1186/s40814-020-00594-1.].
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http://dx.doi.org/10.1186/s40814-020-00614-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7236369PMC
May 2020

A single-arm feasibility cohort study of rivaroxaban in antiphospholipid syndrome.

Pilot Feasibility Stud 2020 25;6:52. Epub 2020 Apr 25.

1Department of Medicine, McMaster University, 1280 Main St. W, Hamilton, ON L8S 4L8 Canada.

Background: There is uncertainty regarding the safety and effectiveness of direct oral anticoagulant agents in patients with antiphospholipid syndrome (APS). We performed a multicenter feasibility study to examine our ability to identify and obtain consent from eligible APS patients and to obtain 95% adherence with daily rivaroxaban administration, in order to inform and power a larger study. Clinical outcomes of bleeding and thrombosis were also collected.

Methods: APS patients with prior venous thromboembolism (VTE) were recruited over 2 years (Oct 2014-Sept 2016) and followed for ≥ 1 year. Patients were assessed clinically every 3 months and had pill counts performed every 6 months. Numbers of patients fulfilling study criteria, as well as those consenting to participate, were tracked, and percentage adherence based on pill counts was recorded. These data were compared against the feasibility endpoints. Rates of thrombosis and bleeding were calculated. Criterion for feasibility was obtaining consent from 135 of 150 identified APS patients over 2 years.

Results: Ninety-six eligible patients were identified, and 14 declined participation. Eighty-two patients were followed for a mean of 19 months, representing 129.8 patient-years. Average rivaroxaban adherence was 95.0%. During follow-up, there were 4 thromboembolic events (2 cerebrovascular and 2 VTE). There were no episodes of major bleeding.

Conclusions: Adequately powered comparative trials using patient-important outcomes in APS are unlikely to be successful due to inability to recruit sufficient numbers of study subjects. This study does not reveal a higher than expected risk of recurrent thromboembolic disease compared to historical cohorts; however, this is an uncontrolled study in relatively low-risk APS patients.

Trial Registration: The study was registered with clinicaltrials.gov, identifier NCT02116036, April 16, 2014.
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http://dx.doi.org/10.1186/s40814-020-00594-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7183116PMC
April 2020

Venous limb gangrene and pulseless electrical activity (PEA) cardiac arrest during management of deep-vein thrombosis and progressive limb ischemic necrosis following vascular surgery.

Am J Hematol 2020 06 20;95(6):712-717. Epub 2020 Mar 20.

Department of Pathology and Molecular Medicine, and Department of Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.

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http://dx.doi.org/10.1002/ajh.25768DOI Listing
June 2020

Development of an INR for rivaroxaban monitoring using plasma samples from patients.

Thromb Res 2020 03 10;187:122-124. Epub 2020 Jan 10.

Department of Medicine, Jewish General Hospital, McGill University, Montreal, Canada. Electronic address:

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http://dx.doi.org/10.1016/j.thromres.2020.01.009DOI Listing
March 2020

Perioperative Management of Patients With Atrial Fibrillation Receiving a Direct Oral Anticoagulant.

JAMA Intern Med 2019 Nov;179(11):1469-1478

Department of Anesthesiology, Hamilton Health Sciences, McMaster University, Hamilton, Ontario, Canada.

Importance: Patients with atrial fibrillation (AF) who use a direct oral anticoagulant (DOAC) and request elective surgery or procedure present a common clinical situation yet perioperative management is uncertain.

Objective: To investigate the safety of a standardized perioperative DOAC management strategy.

Design, Setting, And Participants: The Perioperative Anticoagulation Use for Surgery Evaluation (PAUSE) cohort study conducted at 23 clinical centers in Canada, the United States, and Europe enrolled and screened patients from August 1, 2014, through July 31, 2018. Participants (n = 3007) had AF; were 18 years of age or older; were long-term users of apixaban, dabigatran etexilate, or rivaroxaban; were scheduled for an elective surgery or procedure; and could adhere to the DOAC therapy interruption protocol.

Interventions: A simple standardized perioperative DOAC therapy interruption and resumption strategy based on DOAC pharmacokinetic properties, procedure-associated bleeding risk, and creatinine clearance levels. The DOAC regimens were omitted for 1 day before a low-bleeding-risk procedure and 2 days before a high-bleeding-risk procedure. The DOAC regimens were resumed 1 day after a low-bleeding-risk procedure and 2 to 3 days after a high-bleeding-risk procedure. Follow-up of patients occurred for 30 days after the operation.

Main Outcomes And Measures: Major bleeding and arterial thromboembolism (ischemic stroke, systemic embolism, and transient ischemic attack) and the proportion of patients with an undetectable or minimal residual anticoagulant level (<50 ng/mL) at the time of the procedure.

Results: The 3007 patients with AF (mean [SD] age of 72.5 [9.39] years; 1988 men [66.1%]) comprised 1257 (41.8%) in the apixaban cohort, 668 (22.2%) in the dabigatran cohort, and 1082 (36.0%) in the rivaroxaban cohort; 1007 patients (33.5%) had a high-bleeding-risk procedure. The 30-day postoperative rate of major bleeding was 1.35% (95% CI, 0%-2.00%) in the apixaban cohort, 0.90% (95% CI, 0%-1.73%) in the dabigatran cohort, and 1.85% (95% CI, 0%-2.65%) in the rivaroxaban cohort. The rate of arterial thromboembolism was 0.16% (95% CI, 0%-0.48%) in the apixaban cohort, 0.60% (95% CI, 0%-1.33%) in the dabigatran cohort, and 0.37% (95% CI, 0%-0.82%) in the rivaroxaban cohort. In patients with a high-bleeding-risk procedure, the rates of major bleeding were 2.96% (95% CI, 0%-4.68%) in the apixaban cohort and 2.95% (95% CI, 0%-4.76%) in the rivaroxaban cohort.

Conclusions And Relevance: In this study, patients with AF who had DOAC therapy interruption for elective surgery or procedure, a perioperative management strategy without heparin bridging or coagulation function testing was associated with low rates of major bleeding and arterial thromboembolism.
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http://dx.doi.org/10.1001/jamainternmed.2019.2431DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6686768PMC
November 2019

Peri-Operative Eltrombopag or Immune Globulin for Patients with Immune Thrombocytopaenia (The Bridging ITP Trial): Methods and Rationale.

Thromb Haemost 2019 Mar 27;119(3):500-507. Epub 2019 Jan 27.

Department of Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.

Background:  The Bridging ITP Trial is an open-label randomized trial designed to compare the oral thrombopoietin receptor agonist eltrombopag and intravenous immune globulin (IVIG) for patients with immune thrombocytopaenia (ITP) who require an increase in platelet count before elective surgery. Here, we report the study methods and rationale.

Methods:  We designed a multi-centre, non-inferiority randomized trial comparing daily oral eltrombopag starting 3 weeks pre-operatively, and IVIG administered 1 week pre-operatively for patients with ITP requiring a platelet count increase prior to surgery. Starting dose of eltrombopag is 50 mg daily with a weekly pre-operative dose titration schedule, and treatment is continued for 1 week after surgical haemostasis is achieved. IVIG is administered at a dose of 1 to 2 g/kg 1 week pre-operatively with the allowance for a second dose within 1 week after surgical haemostasis. The objective of the study is to demonstrate non-inferiority of eltrombopag for the primary endpoint of achieving the pre-operative platelet count threshold (50 × 10/L for minor surgery; or 100 × 10/L for major surgery) and sustaining platelet count levels above the threshold for 1 week after surgical haemostasis is achieved, without the use of rescue treatment. Secondary endpoints include thrombosis, bleeding and patient satisfaction.

Conclusion:  The Bridging ITP Trial will evaluate the efficacy and safety of eltrombopag as an alternative to IVIG in the peri-operative setting for patients with ITP. The protocol was designed to provide a management strategy that can be applied in clinical practice. CLINICALTRIALS.

Gov Identifier:  NCT01621204.
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http://dx.doi.org/10.1055/s-0038-1677531DOI Listing
March 2019

Deep Vein Thrombosis Induced by Stasis in Mice Monitored by High Frequency Ultrasonography.

J Vis Exp 2018 04 13(134). Epub 2018 Apr 13.

Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University; Department of Medicine, Jewish General Hospital, McGill University;

Venous thrombosis is a common condition affecting 1 - 2% of the population, with an annual incidence of 1 in 500. Venous thrombosis can lead to death through pulmonary embolism or results in the post-thrombotic syndrome, characterized by chronic leg pain, swelling, and ulceration, or in chronic pulmonary hypertension resulting in significant chronic respiratory compromise. This is the most common cardiovascular disease after myocardial infarction and ischemic stroke and is a clinical challenge for all medical disciplines, as it can complicate the course of other disorders such as cancer, systemic disease, surgery, and major trauma. Experimental models are necessary to study these mechanisms. The stasis model induces consistent thrombus size and a quantifiable amount of thrombus. However, it is necessary to systematically ligate side branches of the inferior vena cava to avoid variability in thrombus sizes and any erroneous data interpretation. We have developed a non-invasive technique to measure thrombus size using ultrasonography. Using this technique, we can assess thrombus development and resolution over time in the same animal. This approach limits the number of mice required for quantification of venous thrombosis consistent with the principle of replacement, reduction, and refinement of animals in research. We have demonstrated that thrombus weight and histological analysis of thrombus size correlate with measurement obtained with ultrasonography. Therefore, the current study describes how to induce deep vein thrombosis in mice using the inferior vena cava stasis model and how to monitor it using high frequency ultrasound.
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http://dx.doi.org/10.3791/57392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5933507PMC
April 2018

Rationale, design, and preliminary results of the Quebec Warfarin Cohort Study.

Clin Cardiol 2018 May 15;41(5):576-585. Epub 2018 May 15.

Université de Montréal Beaulieu-Saucier Pharmacogenomics Centre, Montreal, Quebec, Canada.

Over- and undercoagulation with warfarin are associated with hemorrhagic and thromboembolic events, respectively. Genetic and clinical factors affect warfarin response, and the causes of this variability remain unclear. We present descriptive statistics and test for predictors of poor anticoagulation control. The Quebec Warfarin Cohort (QWC) comprises 1059 new warfarin users, with prospective follow-up using telephone questionnaires every 3 months for 1 year, and using healthcare administrative databases (RAMQ and Med-Echo) for 5 years prior to cohort entry and up to 10 years following active patient participation. Genetic material was collected, and genotyping of CYP2C9 and VKORC1 genes was conducted. Measured outcomes included the percentage of time patients spent within therapeutic range, anticoagulation control, warfarin dose, bleeding, and thromboembolic events. We report baseline characteristics and outcomes after 1 year of follow-up. Poor anticoagulation control was defined as time in therapeutic range <60% in the 3- to 12-month interval. Participants had a mean age of 71 years, and 62% were men. The most common indication for warfarin was atrial fibrillation (87%). Mean time in therapeutic range was 56% (±25%) in the 3 months following warfarin initiation, and 70% (±21%) in the 3- to 12-month interval. During follow-up, the rate of stroke or systemic embolism was 1.8 events per 100 person-years; for major bleeding events, 3.3 events per 100 person-years. Independent predictors of poor anticoagulation control were chronic kidney disease, heart failure, dyslipidemia, and age. The QWC represents a good research cohort to investigate clinical and genetic factors in a warfarin-anticoagulated population.
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http://dx.doi.org/10.1002/clc.22948DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6490141PMC
May 2018

The Perioperative Anticoagulant Use for Surgery Evaluation (PAUSE) Study for Patients on a Direct Oral Anticoagulant Who Need an Elective Surgery or Procedure: Design and Rationale.

Thromb Haemost 2017 12 6;117(12):2415-2424. Epub 2017 Dec 6.

Department of Medicine, University of Toronto, Toronto, Canada.

Background The perioperative management of patients who take a direct oral anticoagulant (DOAC) for atrial fibrillation and require treatment interruption for an elective surgery/procedure is a common clinical scenario for which best practices are uncertain. The Perioperative Anticoagulant Use for Surgery Evaluation (PAUSE) study is designed to address this unmet clinical need. We discuss the rationale for the PAUSE design and analysis plan as well as the rationale supporting the perioperative DOAC protocol. Methods PAUSE is a prospective study with three parallel cohorts, one for each DOAC, to assess a standardized but patient-specific perioperative management protocol for DOAC-treated patients with atrial fibrillation. The perioperative protocol accounts for DOAC type, patient's renal function and surgery/procedure-related bleeding risk. The primary study aim is to demonstrate the safety of the PAUSE protocol for the perioperative management of each DOAC. The secondary aim is to determine the effect of the pre-procedure interruption on residual anticoagulation when measured by the dilute thrombin time for dabigatran and anti-factor Xa levels for rivaroxaban and apixaban. The study hypothesis is that the perioperative management protocol for each DOAC is safe for patient care, defined by expected risks for major bleeding of 1% (80% power to exclude 2%), and for arterial thromboembolism of 0.5% (80% power to exclude 1.5%) in each DOAC group. Conclusion The PAUSE study has the potential to establish a standard-of-care approach for the perioperative management of DOAC-treated patients. The PAUSE management protocol is designed to be easily applied in clinical practice, as it is standardized and also patient specific.
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http://dx.doi.org/10.1160/TH17-08-0553DOI Listing
December 2017

Gas6 Promotes Inflammatory (CCR2CX3CR1) Monocyte Recruitment in Venous Thrombosis.

Arterioscler Thromb Vasc Biol 2017 07 27;37(7):1315-1322. Epub 2017 Apr 27.

From the Lady Davis Institute for Medical Research (S.L., F.-R.B., T.E., Y.K., R.N.R., S.L., C.A.L., M.D.B.); and Department of Medicine (S.L., C.A.L., M.D.B.), Jewish General Hospital, McGill University, Montreal, Québec, Canada.

Objective: Coagulation and inflammation are inter-related. Gas6 (growth arrest-specific 6) promotes venous thrombosis and participates to inflammation through endothelial-innate immune cell interactions. Innate immune cells can provide the initiating stimulus for venous thrombus development. We hypothesize that Gas6 promotes monocyte recruitment during venous thrombosis.

Approach And Results: Deep venous thrombosis was induced in wild-type and Gas6-deficient (-/-) mice using 5% FeCl and flow reduction in the inferior vena cava. Total monocyte depletion was achieved by injection of clodronate before deep venous thrombosis. Inflammatory monocytes were depleted using an anti-C-C chemokine receptor type 2 (CCR2) antibody. Similarly, injection of an anti-chemokine ligand 2 (CCL2) antibody induced CCL2 depletion. Flow cytometry and immunofluorescence were used to characterize the monocytes recruited to the thrombus. In vivo, absence of Gas6 was associated with a reduction of monocyte recruitment in both deep venous thrombosis models. Global monocyte depletion by clodronate leads to smaller thrombi in wild-type mice. Compared with wild type, the thrombi from Gas6 mice contain less inflammatory (CCR2CXCR1) monocytes, consistent with a Gas6-dependent recruitment of this monocyte subset. Correspondingly, selective depletion of CCR2CXCR1 monocytes reduced the formation of venous thrombi in wild-type mice demonstrating a predominant role of the inflammatory monocytes in thrombosis. In vitro, the expression of both CCR2 and CCL2 were Gas6 dependent in monocytes and endothelial cells, respectively, impacting monocyte migration. Moreover, Gas6-dependent CCL2 expression and monocyte migration were mediated via JNK (c-Jun N-terminal kinase).

Conclusions: This study demonstrates that Gas6 specifically promotes the recruitment of inflammatory CCR2CXCR1 monocytes through the regulation of both CCR2 and CCL2 during deep venous thrombosis.
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http://dx.doi.org/10.1161/ATVBAHA.116.308925DOI Listing
July 2017

A multicenter prospective study of risk factors and treatment of unusual site thrombosis.

Thromb Res 2016 Aug 26;144:100-5. Epub 2016 Apr 26.

Medicine and Clinical Epidemiology, Jewish General Hospital, Montreal, Canada. Electronic address:

Unusual site deep vein thrombosis (USDVT) is an uncommon form of venous thromboembolism (VTE) with heterogeneity in pathophysiology and clinical features. While the need for anticoagulation treatment is generally accepted, there is little data on optimal USDVT treatment. The TRUST study aimed to characterize the epidemiology, treatment and outcomes of USDVT. From 2008 to 2012, 152 patients were prospectively enrolled at 4 Canadian centers. After baseline, patients were followed at 6, 12 and 24months. There were 97 (64%) cases of splanchnic, 33 (22%) cerebral, 14 (9%) jugular, 6 (4%) ovarian and 2 (1%) renal vein thrombosis. Mean age was 52.9years and 113 (74%) cases were symptomatic. Of 72 (47%) patients tested as part of clinical care, 22 (31%) were diagnosed with new thrombophilia. Of 138 patients evaluated in follow-up, 66 (48%) completed at least 6months of anticoagulation. Estrogen exposure or inflammatory conditions preceding USDVT were commonly associated with treatment discontinuation before 6months, while previous VTE was associated with continuing anticoagulation beyond 6months. During follow-up, there were 22 (16%) deaths (20 from cancer), 4 (3%) cases of recurrent VTE and no fatal bleeding events. Despite half of USDVT patients receiving <6months of anticoagulation, the rate of VTE recurrence was low and anticoagulant treatment appears safe. Thrombophilia testing was common and thrombophilia prevalence was high. Further research is needed to determine the optimal investigation and management of USDVT.
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http://dx.doi.org/10.1016/j.thromres.2016.04.014DOI Listing
August 2016

Prostaglandin E synthase is upregulated by Gas6 during cancer-induced venous thrombosis.

Blood 2016 Feb 19;127(6):769-77. Epub 2015 Nov 19.

Lady Davis Institute and Department of Medicine, Jewish General Hospital, McGill University, Montreal, QC, Canada.

Venous thromboembolism is a common complication of cancer. Based on recent evidence that (1) growth arrest-specific 6 (Gas6) regulates the expression of tissue factor during venous thrombosis, and (2) cancer promotes a procoagulant milieu, we hypothesize that Gas6 may be involved in cancer-induced coagulopathy. Venous thrombi were induced in both wild-type (WT) and Gas6-deficient ((-/-)) mice with cancer. WT mice with cancer developed larger thrombi than their healthy counterparts; these larger thrombi induced by cancer were not seen in Gas6(-/-) mice. Whole genome microarray analysis of differential gene expression in WT and Gas6(-/-) endothelial cells exposed to M27 murine lung carcinoma cells reveal that Gas6 increases prostaglandin E synthase (Ptges) expression in endothelial cells. This was confirmed using real-time polymerase chain reaction and immunofluorescence staining. Culture of WT endothelial cells with M27 increases the secretion of prostaglandin E2 (PGE2), the enzymatic product of Ptges, in WT but not in Gas6(-/-) endothelial cells. In WT endothelial cells, Ptges expression was regulated through extracellular signal-regulated kinase 1/2 phosphorylation (ERK1/2). In vitro, PGE2 activates platelets after binding to its receptor, EP3. In vivo, EP3 receptor antagonism reversed the effect of cancer-induced thrombosis in WT mice. These results show that Gas6, through upregulation of PGE2, contributes to cancer-induced venous thrombosis.
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http://dx.doi.org/10.1182/blood-2015-02-628867DOI Listing
February 2016

Perioperative Management of Dabigatran: A Prospective Cohort Study.

Circulation 2015 Jul 12;132(3):167-73. Epub 2015 May 12.

From Department of Medicine, McMaster University and Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada (S. Schulman, F.A.S., J.D.D.); Department of Hematology, Karolinska Institutet, Stockholm, Sweden (S. Schulman); Department of Medicine, Ottawa Hospital Research Institute at the University of Ottawa, ON, Canada (M.C.); Division of Hematology, University of British Columbia and Vancouver Coastal Health, Canada (A.Y.Y.L.); Faculty of Medicine, Dalhousie University, Halifax, NS, Canada (S. Shivakumar); Division of Hematology, Department of Medicine, Jewish General Hospital (M.B.) and Department of Medicine (S. Solymoss), McGill University, Montreal, QC, Canada; and McMaster Transfusion Research Program, McMaster University, Hamilton, ON, Canada (R.B., G.W., N.H.).

Background: The perioperative management of dabigatran in clinical practice is heterogeneous. We performed this study to evaluate the safety of perioperative management of dabigatran using a specified protocol.

Methods And Results: Patients treated with dabigatran and planned for an invasive procedure were eligible for inclusion. The timing of the last dose of dabigatran before the procedure was based on the creatinine clearance and procedure-related bleeding risk. Resumption of dabigatran was prespecified according to the complexity of the surgery and consequences of a bleeding complication. Patients were followed up for 30 days for major bleeding (primary outcome), minor bleeding, arterial thromboembolism, and death. We included 541 cases: 324 procedures (60%) with standard risk of bleeding and 217 procedures (40%) with increased risk of bleeding. The last dose of dabigatran was at 24, 48, or 96 hours before surgery according to the protocol in 46%, 37%, and 6%, respectively, of the patients. Resumption was timed according to protocol in 77% with 75 mg as the first dose on the day of procedure in 40% of the patients. Ten patients (1.8%; 95% confidence interval, 0.7-3.0) had major bleeding, and 28 patients (5.2%; 95% confidence interval, 3.3-7.0) had minor bleeding events. The only thromboembolic complication was transient ischemic attack in 1 patient (0.2%; 95% confidence interval, 0-0.5), and there were 4 deaths unrelated to bleeding or thrombosis. Bridging was not used preoperatively but was administered in 9 patients (1.7%) postoperatively.

Conclusion: Our protocol for perioperative management of dabigatran appears to be effective and feasible.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.115.015688DOI Listing
July 2015

Time-dependent hardening of blood clots quantitatively measured in vivo with shear-wave ultrasound imaging in a rabbit model of venous thrombosis.

Thromb Res 2014 Feb 12;133(2):265-71. Epub 2013 Nov 12.

Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center (CRCHUM), Montreal, QC, Canada; Department of Radiology, Radio-Oncology and Nuclear Medicine and Institute of Biomedical Engineering, University of Montreal, Montreal, QC, Canada. Electronic address:

Objective: Provide in vivo blood clot hardening evolution with ultrasound using supersonic imaging of shear waves.

Methods: We conducted a prospective study in flow stasis-induced venous thrombosis within jugular veins of white female New Zealand rabbits. Blood clot elasticity was noninvasively measured in vivo using the Young's modulus (in kilopascals), on a 2-hour and a 2-week periods after thrombus induction. Monitoring was followed by a necropsy and ex vivo mechanical characterization to validate the existence and elasticity of explanted thrombi.

Results: Stagnant blood in the region of interest underwent clotting and progressive hardening with thrombus aging. The mean Young's moduli varied from 1.0 ± 0.6 kPa (at 10 min) to 5.3 ± 1.6 kPa (at 2 hours), then to 25.0 ± 6.8 kPa (at 14 days) post-surgery. Mean ex vivo moduli of 6.2 ± 0.7 kPa at 2 hours and 29.0 ± 2.4 kPa at 2 weeks agreed with in vivo measures.

Conclusions: Supersonic imaging of shear waves provides consistent quantitative non-invasive elasticity measurements not available with standard compression ultrasound imaging for diagnosing and following venous thromboembolism. This information translatable to humans could aid in determining whether continued anticoagulant treatment is necessary, especially in the setting of unprovoked venous thromboembolism.
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http://dx.doi.org/10.1016/j.thromres.2013.11.001DOI Listing
February 2014

Correlation between CHADS2 score and anticoagulant use in atrial fibrillation: Results of a mini-survey.

Exp Clin Cardiol 2013 ;18(2):101-3

Department of Professional Services, Sir Mortimer B Davis Jewish General Hospital, Montreal, Quebec.

Quality assurance in atrial fibrillation is related to the appropriate use of anticoagulation. The CHADS2 score is widely used to determine which patients should or should not be anticoagulated. The authors hypothesized that as thromboembolic risk and, therefore, the CHADS2 score increases, so should the rate of anticoagulant prescription. The authors found a positive correlation between CHADS2 score and anticoagulant prescription (r=0.8) in a mini-survey. Although anticoagulant use at CHADS2 score = 0 was presumed to be very low, it was found to be higher than expected. This was readily explained by a group of low-risk patients being anticoagulated before cardioversion. Cardioverted patients were then examined as a group and it was found that the rate of rhythm control decreased with CHADS2 score (r= -0.89), a finding that has not been reported in the literature and may warrant further investigation.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3718585PMC
August 2013

Amphiphilic peptide-loaded nanofibrous calcium phosphate microspheres promote hemostasis in vivo.

Acta Biomater 2013 Nov 21;9(11):9194-200. Epub 2013 Jun 21.

Lady Davis Institute for Medical Research, Department of Medicine, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.

Most fatalities from trauma occur due to severe blood loss. There is a need for improved hemostatic biomaterials that can address this problem. The aim of this study was to determine the in vivo efficacy of nanofibrous microspheres (NFM) loaded with hemostatic peptides, specifically ideal amphipathic peptides (IAP) that have been demonstrated to possess both procoagulant and antifibrinolyic activities. We demonstrate that IAP can be coupled to NFM (IAP-NFM) to form matrices that exhibit substantial hemostatic activity. IAP-NFM matrices were compared to a commercial zeolitic hemostatic biomaterial (QuikClot) and have superior efficacy in reducing bleeding in vivo. In both a murine tail transection and a murine hepatic injury model, bleeding times were significantly reduced (P<0.05) with the use of IAP-NFM as compared with equal masses of either QuikClot or NFM alone, or no treatment. Importantly, histological examination revealed no tissue injury when IAP-NFM or NFM were applied to hepatic lacerations. In contrast, QuikClot caused widespread hepatocyte degeneration and necrosis, with higher average injury zone thickness as determined by semiquantitative analysis. In summary, NFM was able to maintain the pro-coagulant properties of IAP in our preclinical model, caused no observable tissue damage at the site of application and had better performance than QuikClot controls.
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http://dx.doi.org/10.1016/j.actbio.2013.06.023DOI Listing
November 2013

Vascular Gas6 contributes to thrombogenesis and promotes tissue factor up-regulation after vessel injury in mice.

Blood 2013 Jan 13;121(4):692-9. Epub 2012 Nov 13.

Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal, QC, Canada.

Gas6 (growth-arrest specific gene 6) plays a role in thrombus stabilization. Gas6 null (-/-) mice are protected from lethal venous and arterial thromboembolism through platelet signaling defects induced only by 5 μM ADP and 10 μM of the thromboxane analog, U46619. This subtle platelet defect, despite a dramatic clinical phenotype, raises the possibility that Gas6 from a source other than platelets contributes to thrombus formation. Thus, we hypothesize that Gas6 derived from the vascular wall plays a role in venous thrombus formation. Bone marrow transplantation and platelet depletion/reconstitution experiments generating mice with selective ablations of Gas6 from either the hematopoietic or nonhematopoietic compartments demonstrate an approximately equal contribution by Gas6 from both compartments to thrombus formation. Tissue factor expression was significantly reduced in the vascular wall of Gas6(-/-) mice compared with WT. In vitro, thrombin-induced tissue factor expression was reduced in Gas6(-/-) endothelial cells compared with wild-type endothelium. Taken together, these results demonstrate that vascular Gas6 contributes to thrombus formation in vivo and can be explained by the ability of Gas6 to promote tissue factor expression and activity. These findings support the notion that vascular wall-derived Gas6 may play a pathophysiologic role in venous thromboembolism.
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http://dx.doi.org/10.1182/blood-2012-05-433730DOI Listing
January 2013

Atrial fibrillation-associated remodeling does not promote atrial thrombus formation in canine models.

Circ Arrhythm Electrophysiol 2012 Dec 24;5(6):1168-75. Epub 2012 Oct 24.

Department of Medicine and Research Center, Montreal Heart Institute and Université de Montréal, Quebec, Canada.

Background: The most important complication of atrial fibrillation (AF) is thromboembolic stroke. Although AF-related remodeling is considered important in atrial thrombogenesis, its role never has been directly tested. This study assessed effects of AF-related remodeling on the atrial thrombogenic milieu by using radiofrequency ablation (RFA) to create a quantifiable prothrombotic nidus.

Methods And Results: We studied normal control dogs (control, n=16) and 3 canine AF-models: (1) atrial tachycardia remodeling (ATR; n=16) induced by atrial tachypacing (400 bpm for 1 week, with atrioventricular block and ventricular pacing at 80 bpm); (2) congestive heart failure (CHF; n=14) attributable to ventricular tachypacing (240 bpm for 2 weeks); and (3) chronic AF (CAF; n=8) induced by atrial tachypacing (35±3 days) without atrioventricular block. CAF dogs had AF for 13±1 days until euthanization. After remodeling was established, RFA lesions were created in both atria. Half the ATR and CHF dogs were subjected to atrial tachypacing during 7-day post-RFA follow-up. Electrophysiological and echocardiographic studies were performed before RFA and 7 days after RFA, and then hearts were removed and atrial thrombi were quantified by histomorphometry. Burst-pacing-induced AF duration was significantly greater in ATR, CHF, and CAF groups versus control group. The atrial effective refractory period shortened in ATR and CAF groups. Left atrial diameter was significantly larger with CHF, but not with ATR. Neither total thrombus volume nor thrombus volume per lesion differed significantly among groups. Table.Properties of Ablation Lesions and Atrial Thrombi Experimental GroupControl (n=16)ATR (n=16)CHF (n=14)CAF (n=8)N of ablation lesions per dog6.9±0.36.6±0.27.2±0.26.9±0.4Ablation lesion area, mm(2)53.1±3.558.3±4.857.7±4.944.3±3.7Ablation lesion depth, mm5.2±0.25.1±0.35.3±0.25.2±0.2Ablation lesion volume, mm(3)205.2±17.8211.6±17.6231.5±29.0176.8±22.2N of thrombi per dog5.4±0.44.7±0.35.6±0.46.5±0.4Presence of thrombus, %80±572±577±695±3Mean thrombus volume in both atria, mm(3)20.8±3.414.9±2.212.2±2.622.5±5.6Mean thrombus volume in left atria, mm(3)8.2±1.54.0±0.95.5±1.68.1±3.3Mean thrombus volume in right atria, mm(3)30.1±5.422.7±4.317.9±4.132.8±8.3Total thrombus volume in both atria, mm(3)140.5±21.399.7±16.886.1±17.5131.1±22.7Total thrombus volume in left atria, mm(3)22.8±5.311.8±3.317.0±3.723.3±6.4Total thrombus volume in right atria, mm(3)117.7±21.587.8±17.269.1±16.1107.8±23.3Thrombus volume normalized to ablation lesion area in both atria, mm(3)/mm(2)0.5±0.10.4±0.11.5±1.10.8±0.3Thrombus volume normalized to ablation lesion volume in both atria0.2±0.10.1±0.00.5±0.40.3±0.1 ATR indicates atrial tachycardia remodeling; CAF, chronic atrial fibrillation; and CHF, congestive heart failure. There were no statistically significant differences for any groups vs control group for any of these variables studied.

Conclusions: None of the AF substrates tested, including sustained atrial tachycardia/AF itself, enhanced post-RFA atrial thrombus formation. Indices of electrical and structural remodeling did not predict post-RFA thrombogenic potential. Contrary to widely held but previously untested notions, we were unable to demonstrate prothrombotic effects of AF-related remodeling.
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http://dx.doi.org/10.1161/CIRCEP.112.974410DOI Listing
December 2012

The effectiveness and safety of fixed low-dose prothrombin complex concentrates in patients requiring urgent reversal of warfarin.

Transfusion 2013 Jul 15;53(7):1451-8; quiz 1450. Epub 2012 Oct 15.

Departments of Medicine and Epidemiology, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.

Background: A rapid method of reversal is required for patients on warfarin who suffer acute bleeding or require emergency surgery. Prothrombin complex concentrates (PCCs) have recently been recommended by the Canadian Blood Services for use at a fixed low dose of 1000 IU of Factor (F)IX activity. The main goal of this study was to investigate both the effectiveness and the safety of fixed low-dose PCCs.

Study Design And Methods: We retrospectively reviewed charts from 103 patients who received PCCs for reversal of warfarin therapy.

Results: A total of 103 patients were treated with PCC at a single fixed dose of 1000 IU of F IX activity. Fifty patients (48.5%) had a final international normalized ratio (INR) response of not more than 1.5 and an additional 45 patients (43.7%) had a final INR response between 1.6 and 2.0. However, 86 patients (83.5%) had an excellent clinical response consisting of control of bleeding without the requirement of additional measures. In a multivariable model, patients who received fresh-frozen plasma and patients who were given doses greater than 1000 IU of PCC were both identified as predictors of a poor clinical response (odds ratio [OR] 3.48, 95% confidence interval [CI] 0.76-15.89, p = 0.11; and OR 10.8, 95% CI 2.08-56.28, 95% CI, p = 0.005, respectively). There were five adverse events up to 30 days after PCC use.

Conclusion: At a fixed dose of 1000 IU of F IX activity, PCC seems to be effective and safe but randomized controlled trials, specifically examining different doses of PCC, are required to confirm the above observations.
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http://dx.doi.org/10.1111/j.1537-2995.2012.03924.xDOI Listing
July 2013

Management and adherence to VTE treatment guidelines in a national prospective cohort study in the Canadian outpatient setting. The Recovery Study.

Thromb Haemost 2012 Sep 10;108(3):493-8. Epub 2012 Jul 10.

Centre for Clinical Epidemiology, Jewish General Hospital, Montreal, Quebec, Canada.

Documenting patterns and outcomes of venous thromboembolism (VTE) management and degree of adherence by clinicians to treatment guidelines could help identify remediable gaps in patient care. Prospective, clinical practice-based data from Canadian outpatient settings on management of VTE, degree of adherence with treatment guidelines and frequency of recurrent VTE and bleeding during follow-up was obtained in a multicentre, prospective observational study. From 12 Canadian centres, we assessed 868 outpatients with acute symptomatic VTE who received the low-molecular-weight heparin (LMWH) enoxaparin alone or with vitamin K antagonists (VKA), at baseline and at six months (or at the end of treatment, whichever came first). Index VTE was limb deep venous thrombosis (DVT) in 583 (67.2%) patients, pulmonary embolism (PE) with or without DVT in 262 (30.2%) patients, and unusual site DVT in 23 (2.6%) patients. VTE was unprovoked in 399 (46.0%) patients, associated with cancer in 74 (8.5%) patients, transient risk factors in 327 (37.7%) patients and hormonal factors in 68 (7.8%) patients.With regard to guideline adherence, 58 (7.3%) patients received <5 days LMWH and 114 (14.5%) had overlap <1 day. Among patients with cancer-related VTE, 59.5% were prescribed LMWH monotherapy and 43.2% received such treatment for >3 months. Only 38.1% of patients with transient VTE risk factors had received thromboprophylaxis. Our study provides useful information on clinical presentation, management and related outcomes in Canadian outpatients with VTE. Our results suggest there may be important gaps in use of thromboprophylaxis to prevent VTE and use of LMWH monotherapy to treat cancer-related VTE.
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http://dx.doi.org/10.1160/TH12-03-0169DOI Listing
September 2012

Growth arrest-specific gene 6 (gas6) and vascular hemostasis.

Adv Nutr 2012 Mar 1;3(2):196-203. Epub 2012 Mar 1.

Lady Davis Institute for Medical Research, McGill University, Montreal, Quebec, Canada.

Gas6 (growth arrest-specific 6) belongs structurally to the family of plasma vitamin K-dependent proteins. Gas6 has a high structural homology with the natural anticoagulant protein S, sharing the same modular composition. Interestingly, despite the presence of a γ-carboxyglutamic acid domain in its structure, no role in the coagulation cascade has been identified for gas6. Gas6 has been shown to be involved in vascular homeostasis and more precisely is involved in proliferation, apoptosis, efferocytosis, leukocyte migration, and sequestration and platelet aggregation. It is also involved in the activation of different cell types, from platelets to endothelial and vascular smooth muscle cells. Thus, it has been shown to play a role in several pathophysiological processes such as atherosclerosis, cancer, and thrombosis. Interestingly, studies using gas6 null mice highlighted that gas6 may represent a novel potential target for anticoagulant therapy, because these animals are protected from lethal venous thromboembolism without excessive bleeding. However, the mechanism in thrombus occurrence remains to be further explored. In the present review, we will focus on the role of gas6 in innate immunity, atherosclerosis, thrombosis, and cancer-related events.
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http://dx.doi.org/10.3945/an.111.001826DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3648720PMC
March 2012

Surface-attached amphipathic peptides reduce hemorrhage in vivo.

J Trauma Acute Care Surg 2012 Jan;72(1):136-42

Department of Medicine, Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.

Background: The leading causes of death for trauma patients in civilian and combat settings are traumatic brain injury and uncontrolled hemorrhage, respectively. This study examines the hemostatic activity of an ideal amphipathic peptide (IAP) attached to a biocompatible surface.

Methods: Procoagulant properties of IAP attached to a surface were first tested, in vitro, using factor Xa and thrombin generation assays and thromboelastography. Rabbits and swine were used for in vivo studies. Injuries were performed using scalpel blade 11, and free bleeding was allowed for five seconds. While bleeding, IAP coupled to a hydrogel or QuikClot were applied to the wound and the time was recorded until bleeding stopped.

Results: Results show that when IAP is attached to a surface, both factor IXa and factor Xa activities are promoted. Thromboelastography shows that surface-attached IAP results in earlier onset and stronger clot formation. In rabbits, the incorporation of IAP onto a biocompatible hydrogel reduces bleeding times by 40% (p < 0.03). In pigs, bleeding times are reduced 30% to 50% (p < 0.02) by surface-coupled IAP. Finally, using a rabbit liver laceration model, the properties of surface-coupled IAP are less damaging when compared with QuikClot, a currently used material in external hemorrhagic injuries.

Conclusions: This study provides a relevant proof of concept for the development of IAP coupled to a biocompatible surface as a hemostatic agent, that is potentially safer than the commercially available QuikClot.
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http://dx.doi.org/10.1097/TA.0b013e31823183b4DOI Listing
January 2012

Delayed immune-mediated thrombocytopenia after re-exposure to abciximab therapy.

Can J Cardiol 2011 Nov-Dec;27(6):869.e13-4. Epub 2011 Sep 1.

Division of Hematology, Jewish General Hospital, McGill University Montreal, Québec, Canada.

Abciximab is a potent antiplatelet agent that is increasingly being used to prevent ischemic complications of percutaneous coronary revascularization. Thrombocytopenia, including acute profound thrombocytopenia, has been reported to occur with this agent, but usually within 1 to 2 days of exposure. We report the case of a woman aged 68 years who presented with profound delayed thrombocytopenia 9 days after a second exposure to abciximab. She was treated successfully with intravenous immunoglobulin with complete resolution of the thrombocytopenia and no subsequent recurrences.
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http://dx.doi.org/10.1016/j.cjca.2011.05.011DOI Listing
January 2012

Characterization of in vitro hemostatic peptide effects by thromboelastography.

Clin Appl Thromb Hemost 2012 Jan-Feb;18(1):27-34. Epub 2011 Aug 25.

Defence Research and Development Canada, Toronto, Ontario, Canada.

In this study, we validated a thromboelastography (TEG) method to evaluate the hemostatic effects of 3 peptides. The first peptide is an ideal amphipathic peptide composed of 22 leucine and lysine in a ratio of 2:1. At a very low concentration, the peptide had a procoagulant effect shown by decreases in reaction time (R) and coagulation time (K) but was impaired by a decrease in maximum amplitude (MA). At higher concentrations, the peptide had an anticoagulant effect. The α angle was minimally affected by the peptide. The second peptide is melittin derived from bee venom. Melittin showed procoagulant effects reflected by a decrease in clotting time but led to lower MA. The third peptide derived from fibrinogen γ chain promoted hemostasis only at an optimal concentration and became anticoagulant at a higher concentration. The hemostatic mechanisms of each peptide were discussed. Our study would facilitate further development of peptides for either hemorrhage control or thrombosis treatment.
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http://dx.doi.org/10.1177/1076029611412371DOI Listing
June 2012
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