Intravenous thrombolysis for acute ischaemic stroke in patients on direct oral anticoagulants

BACKGROUND AND PURPOSE

Whereas intravenous thrombolysis (IVT) is allowed for acute ischaemic stroke in patients on vitamin K antagonists with international normalized ratio ≤1.7, there are no similar recommendations for patients on direct oral anticoagulants (DOACs), notably due to the lack of coagulation tests to assess the therapeutic effects. Although the literature is scarce, consisting of small case series and retrospective studies, considering the frequency of this situation the French Vascular Neurology Society and the French Study Group on Haemostasis and Thrombosis have worked on a joint position paper to provide a practical position regarding the emergency management of ischaemic stroke in patients on DOACs.

METHOD

Based on a review of the literature, the authors wrote a first text that was submitted to a broad panel of members from the two societies. The text was then amended by the authors to address experts' comments and to reach a consensus.

RESULTS

In patients with normal renal function and who stopped the DOAC for at least 48 h, the management should not differ from that in patients without oral anticoagulant. In patients who are still on DOACs, mechanical thrombectomy is encouraged preferentially when applicable in first line. Otherwise, when specific tests are available, values <50 ng/ml indicate that IVT is allowed. In the absence of specific tests, standard tests (thrombin time, prothrombin time and activated partial thromboplastin time) can be used for dabigatran and rivaroxaban, although interpretation of these tests may be less reliable. In some patients on dabigatran, idarucizumab may be used before IVT.

CONCLUSIONS

In this expert opinion paper, it is suggested that IVT can be performed in patients selected according to the time elapsed since the drug was last taken, renal function, type of hospital where the patient is admitted and plasma concentration of DOAC.

Management of antiplatelet therapy in patients undergoing elective invasive procedures. Proposals from the French Working Group on perioperative haemostasis (GIHP) and the French Study Group on thrombosis and haemostasis (GFHT). In collaboration with the French Society for Anaesthesia and Intensive Care Medicine (SFAR)

The French Working Group on Perioperative Haemostasis (GIHP) and the French Study Group on Haemostasis and Thrombosis (GFHT) in collaboration with the French Society for Anaesthesia and Intensive Care Medicine (SFAR) drafted up-to-date proposals for the management of antiplatelet therapy in patients undergoing elective invasive procedures. The proposals were discussed and validated by a vote; all proposals but one could be assigned with a high strength. The management of antiplatelet therapy is based on their indication and the procedure. The risk of bleeding related to the procedure can be divided into high, moderate and low categories depending on the possibility of performing the procedure in patients receiving antiplatelet agents (none, monotherapy and dual antiplatelet therapy respectively). If discontinuation of antiplatelet therapy is indicated before the procedure, a last intake of aspirin, clopidogrel, ticagrelor and prasugrel 3, 5, 5 and 7 days before surgery respectively is proposed. The thrombotic risk associated with discontinuation should be assessed according to each specific indication of antiplatelet therapy and is higher for patients receiving dual therapy for coronary artery disease (with further refinements based on a few well-accepted items) than for those receiving monotherapy for cardiovascular prevention, for secondary stroke prevention or for lower extremity arterial disease. These proposals also address the issue of the potential role of platelet functional tests and consider management of antiplatelet therapy for regional anaesthesia, including central neuraxial anaesthesia and peripheral nerve blocks, and for coronary artery surgery.

Increased prevalence of factor V Leiden in patients with retinal vein occlusion and under 60 years of age

Retinal vein occlusion (RVO) is a multifactorial disease involving vessel damage, stasis, viscosity and thrombosis. Conflicting findings on hereditary thrombophilic risk factors have been reported and their impact on RVO features remains to be defined. The aim of the present study was to evaluate the prevalence of hereditary thrombophilic risk factors (HTRF) and characteristics of RVO in patients with or without HTRF. The design of the study was a prospective, observational case series. Two hundred and thirty-four patients with RVO were included consecutively. A French healthy population of the same region was studied as control group. The HTRF studied were protein C (PC), protein S (PS) and antithrombin (AT) deficiencies, factor V Leiden (FVL) and factor II 20210A polymorphisms. Chi-Square was used for comparison with the healthy subjects and between RVO patient with and without HTRF according to localisation (branch vs. central), type of RVO (ischemic or non-ischemic), recurrence, age at first event and classical vascular risk factors. Twenty-two patients had HTRF (12 FV Leiden heterozygotes, 9 FII 20210A heterozygotes and 1 PS deficiency). No AT or PC deficiency was detected. Frequencies of PS deficiency, FVL and FII 20210A allele were similar to the reference population as well as to published data in the general caucasian population. Eighty-six patients experienced their first episode before the age of 60 years. Systemic hypertension, glaucoma and angina were significantly less frequent in patients with RVO before 60 years. Fourteen of the 22 patients with one HTRF (64%) experienced their first episode of RVO before the age of 60 years compared to 72 of 212 without HTRF (34%) (p = 0.006). Heterozygote status for FV Leiden was significantly more frequent in patients who had experienced their first episode of RVO before 60 years (p = 0.027). In conclusion, this study suggests a role of FV Leiden in the occurrence of RVO in patients younger than 60 years who exhibit fewer acquired vascular risk factors than in older patients.

Comparative study of coagulation and thrombin generation in the portal and jugular plasma of patients with cirrhosis

Portal vein thromboses are frequent in cirrhotic patients and may be favoured by hypercoagulability in the splanchnic venous system. The coagulation balance and thrombin generation (TG) were evaluated in platelet-free plasma obtained from portal and systemic blood samples in 28 cirrhotic patients while undergoing transjugular intrahepatic porto-systemic shunt. TG assay (TGA) was performed with all samples from cirrhotic patients and with plasma samples from 14 healthy controls, with varying concentrations of tissue factor and phospholipids, with or without thrombomodulin. Screening tests and specific assays were also performed and activated partial thromboplastin time was shorter in portal plasma samples with higher FVIII and lower protein C levels, well correlated with Child-Pugh scores, and higher D-dimers and F1+2 levels However, all TGA parameters were similar in portal and jugular samples, possibly due in part to similar concentrations of factor II and antithrombin in these two sites of plasma sampling. TGA showed lower thrombin peaks and endogenous thrombin potential values in cirrhotic plasma compared to those of healthy controls. Importantly, a resistance to thrombomodulin that well correlated with factor VIII and PC levels, was evidenced in all samples from patients with cirrhosis, and was more significant in those from severely affected cases. This study therefore supports the existence of a relative hypercoagulability in the portal vein of cirrhotic patients that is likely due to protein C/S deficiency and to high FVIII levels.

Effectiveness of a new immuno-assay for the diagnosis of heparin-induced thrombocytopenia and improved specificity when detecting IgG antibodies

The diagnosis of heparin-induced thrombocytopenia (HIT) is based on clinical criteria and biological assays. Most immunoassays detect antibodies (either IgG alone or additionally IgA and IgM) against PF4 immobilised in wells of microtiter plates with stoichiometric concentrations of polyanion (heparin or polyvinylsulfonate). We studied whether diagnostic sensitivity and/or specificity for HIT could be improved using a novel assay in which unfractionated heparin is immobilised alone to the microwells, with PF4 (and, potentially, other heparin-dependent antigen proteins) provided by adding platelet lysate during the procedure. Samples from 101 patients with suspected HIT and from 101 controls (including 50 with antiphospholipid antibodies) were tested. The global assay (Zymutest HIA IgG/A/M®, Hyphen BioMed) was positive for 39 of 40 patients with definite HIT (positive PF4-specific ELISA and positive serotonin release assay). It was positive in only two of the 101 control patients studied and also in 14 of the 61 patients with suspected HIT for whom the disease was excluded (specificity (sp): 77%). On the other hand, Zymutest HIA IgG®, an IgG-specific assay, was positive in only six patients without HIT (Sp: 90%). Heparin-dependent IgG antibodies were present at higher levels in patients with definite HIT than in those for whom the diagnosis of HIT was ruled out. A single ELISA that detects IgG antibodies is more effective for the diagnosis of HIT in clinical practice. These results also support the hypothesis that heparin-dependent antibodies of IgG class have a major role in the pathogenesis of HIT.

Analyses of the FranceCoag cohort support differences in immunogenicity among one plasma-derived and two recombinant factor VIII brands in boys with severe hemophilia A

Around one third of boys with severe hemophilia A develop inhibitors (neutralizing antibodies) against their therapeutic factor VIII product. This adverse effect may result in more life-threatening bleeding, disability, impaired quality of life, and costly care. We compared the incidence of inhibitors in boys treated with the three factor VIII products most used in France: one plasma-derived (Factane) and two recombinant products (Advate and Kogenate Bayer). A previously untreated cohort of patients was created in 1994 to investigate risk factors for inhibitor development. We selected boys with severe hemophilia A (factor VIII <1 IU/dL) first treated with one of the three factor VIII products studied. Details of product infusions, inhibitor assays and main fixed and time-varying inhibitor risk factors were recorded for the first 75 exposure days. Three outcomes (all inhibitors, high-titer inhibitors and subsequently treated inhibitors) were analyzed by univariate and multivariate Cox models. We studied 395 boys first treated between 2001 and 2016 (131, 137, and 127 with Factane, Advate, and Kogenate Bayer, respectively). Clinically significant inhibitors were diagnosed in 121 patients (70 high-titer). The incidence of high-titer inhibitors was significantly associated with the factor VIII product received (P=0.005): the cumulative incidence at 75 exposure days was 12.7% (95% CI: 7.7-20.6) with Factane, 20.4% (95% CI: 14.0-29.1) with Advate, and 31.6% (95% CI: 23.5-41.7) with Kogenate Bayer. The low inhibitor incidence observed with Factane is concordant with recent findings from the SIPPET randomized trial. These consistent results from observational and experimental studies should lead to improved care for previously untreated patients and cost savings for healthcare systems worldwide.

5B9, a monoclonal antiplatelet factor 4/heparin IgG with a human Fc fragment that mimics heparin-induced thrombocytopenia antibodies

Essentials No humanized monoclonal antibody was available to study heparin-induced thrombocytopenia (HIT). We developed the first anti-platelet factor 4 (PF4)/heparin antibody with a human Fc fragment. This antibody (5B9) fully mimics the effects of human HIT antibodies. 5B9 binds two regions within PF4 that may be critical for the pathogenicity of HIT antibodies.

SUMMARY

Background The diagnosis of heparin-induced thrombocytopenia (HIT) is based on clinical and biological criteria, but a standard is lacking for laboratory assays. Moreover, no humanized HIT antibody is available for pathophysiological studies. Objective To characterise 5B9, a chimeric monoclonal antibody, which fully mimics the effects of human HIT antibodies. Methods/Results 5B9, a chimeric anti-platelet factor 4/heparin complexes IgG1 antibody, was obtained after immunizing specific transgenic mice. 5B9 induced heparin FcγRIIA-dependent platelet aggregation and tissue factor mRNA synthesis in monocytes. It also induced significant thrombocytopenia and thrombin generation in mice expressing human PF4 and FcγRIIA receptors. The binding of 5B9 to PF4/H complexes was inhibited by 15 of 25 HIT plasma samples and only three of 25 samples containing non-pathogenic anti-PF4/H antibodies. KKO, a murine IgG2b HIT antibody, also inhibited the binding of 5B9 to PF4/H, suggesting that epitopes recognized by both antibodies are close. A docking analysis based on VH and VL sequences of 5B9 showed that binding of 5B9 Fab to PF4 involved 12 and 12 residues in B and D monomers, respectively, including seven previously identified as critical to the formation of a PF4/KKO complex. Two regions (Asp-7 to Thr-15 and Ala-32 to Thr-38) therefore appeared important for the binding of 5B9 and KKO on PF4 modified by heparin. Conclusions 5B9 is the first anti-PF4/H monoclonal antibody with a human Fc fragment, which induces similar cellular activation as HIT antibodies. Moreover, 5B9 binds epitopes within PF4 that are likely to be critical for the pathogenicity of HIT antibodies.

[Neonatal arterial ischemic stroke: Which thrombotic biological risk factors to investigate and which practical consequences?]

All biological risk factors that have been previously identified to increase the risk of thrombosis in adults, have also been studied in neonates with arterial Ischemic Stroke (NAIS), but most studies were retrospective and included relatively low numbers of affected children. We therefore could not suggest recommendations with a strong level of evidence and only expert proposals potentially useful for clinical practice will be presented in this text. Despite these limitations, the extensive analysis of published data supported that factor V Leiden (FVL) and increased levels of Lp(a) could be significant risk factors for NAIS. Importantly, these 2 risk factors cannot be considered as having provoked NAIS, and moreover, they do not influence the prognosis and the immediate treatment. However, since the FVL may have an impact for the prescription of a thromboprophylaxis when the neonate will become adult, to look for its presence in affected patients may be justified. For clinical practice, the following propositions can be applied: 1. Routine testing for thrombophilia (AT, PC PS deficiency, FV Leiden or FII20210A) or for detecting other biological risk factors such as antiphospholipid antibodies, high FVIII, homocystein or Lp(a) levels, MTHFR thermolabile variant, should not be considered in neonates with NAIS. 2. Testing for FV Leiden can be performed in case of documented family history of venous thromboembolic disease. 3. Testing neonates for the presence of antiphospholipid antibodies (APA) is mandatory in case of clinical events suggesting antiphospholipid syndrome in the mother (vascular thrombosis, and/or pregnancy morbidity). 4. Routine testing for thrombophilia is not proposed in both parents in case of early death of the neonate, apart from APA in the mother.

Risk factors for heparin-induced thrombocytopenia: Focus on Fcγ receptors

Fcγ receptors have critical roles in the pathophysiology of heparin-induced thrombocytopenia (HIT), a severe immune-mediated complication of heparin treatment. Activation of platelets, monocytes and neutrophils by platelet-activating anti-PF4/heparin IgG antibodies results in thrombocytopenia, hypercoagulability and thrombosis in susceptible patients, effects that depend on FcγRIIA. In addition, FcγRIIIA receptors probably contribute to clearance of platelets sensitised by HIT immune complexes. FcγRI has also been reported to be involved in monocyte activation by HIT IgG antibodies and synthesis of tissue factor. This review focuses on the role of these FcγRs in HIT pathophysiology, including the potential influence of several gene variations associated with variable risk of HIT and related thrombosis. In particular, the 276P and 326Q alleles of CD148, a protein tyrosine phosphatase that regulates FcγRIIA signalling, are associated with a lower risk of HIT, and platelets from healthy donors expressing these alleles are hyporesponsive to anti-PF4/H antibodies. It was also recently demonstrated that the risk of thrombosis is higher in HIT patients expressing the R isoform of the FcγRIIA H131R polymorphism, with HIT antibodies shown to activate RR platelets more efficiently, mainly explained by an inhibitory effect of normal IgG2, which bound to the FcγRIIA 131H isoform more efficiently. Environmental risk factors probably interact with these gene polymorphisms affecting FcγRs, thereby increasing thrombosis risk in HIT.

Expanding the Mutation Spectrum Affecting αIIbβ3 Integrin in Glanzmann Thrombasthenia: Screening of the ITGA2B and ITGB3 Genes in a Large International Cohort

We report the largest international study on Glanzmann thrombasthenia (GT), an inherited bleeding disorder where defects of the ITGA2B and ITGB3 genes cause quantitative or qualitative defects of the αIIbβ3 integrin, a key mediator of platelet aggregation. Sequencing of the coding regions and splice sites of both genes in members of 76 affected families identified 78 genetic variants (55 novel) suspected to cause GT. Four large deletions or duplications were found by quantitative real-time PCR. Families with mutations in either gene were indistinguishable in terms of bleeding severity that varied even among siblings. Families were grouped into type I and the rarer type II or variant forms with residual αIIbβ3 expression. Variant forms helped identify genes encoding proteins mediating integrin activation. Splicing defects and stop codons were common for both ITGA2B and ITGB3 and essentially led to a reduced or absent αIIbβ3 expression; included was a heterozygous c.1440-13_c.1440-1del in intron 14 of ITGA2B causing exon skipping in seven unrelated families. Molecular modeling revealed how many missense mutations induced subtle changes in αIIb and β3 domain structure across both subunits, thereby interfering with integrin maturation and/or function. Our study extends knowledge of GT and the pathophysiology of an integrin.

Significant effect of VEGFA polymorphisms on the clinical outcome of metastatic colorectal cancer patients treated with FOLFIRI-cetuximab

AIM

The efficacy of a cetuximab-based regimen used to treat metastatic colorectal cancer (mCRC) could be influenced by VEGFA polymorphisms.

MATERIALS & METHODS

We studied the effects of five polymorphisms in the VEGFA gene (-2549D/I, -1154G/A, -460T/C, +405G/C and +936C/T) on the outcome of 98 mCRC patients treated with FOLFIRI plus cetuximab.

RESULTS

Patients homozygous for the -2549D, -1154G and -460T alleles did exhibit higher response rates to treatment and longer progression-free survival compared with others. In addition, the DGTGC and IGCGC haplotypes were significantly associated with a lower risk of disease progression.

CONCLUSION

These findings suggest that VEGFA genetic variations might influence response/resistance of FOLFIRI plus cetuximab treatment in mCRC patients.