Feasibility of rapid measurement of Rivaroxaban plasma levels in patients with acute stroke

Mutant CYP3A4/5 Correlated with Clinical Outcomes by Affecting Rivaroxaban Pharmacokinetics and Pharmacodynamics in Patients with Atrial Fibrillation

PURPOSE

This study was designed to investigate the impact of single-nucleotide polymorphism-encoded cytochrome P450 enzymes (CYP3A4/5) on clinical outcomes of rivaroxaban in patients with non-valvular atrial fibrillation (NVAF) based on pharmacokinetics and pharmacodynamics (PK/PD) aspects.

METHOD

A prospective study enrolling 165 rivaroxaban-treated patients with NVAF was conducted. Genotyping of CYP3A4 (rs2242480, rs2246709, rs3735451, and rs4646440) and CYP3A5 (rs776746) was performed to explore their impact on the trough plasma concentrations (Ctrough) of rivaroxaban, coagulation indicators at the Ctrough including activated partial thromboplastin time (APTT) and prothrombin time (PT), and clinical outcomes.

RESULTS

Patients with mutant genotype CYP3A4 (rs2242480, rs2246709, and rs3735451) and CYP3A5 (rs776746) had higher levels of rivaroxaban Ctrough, PT values than that of wild-type. Furthermore, a positive relationship was revealed between Ctrough and PT (r = 0.212, p = 0.007), while no significant correlation was found between Ctrough and APTT. Regarding the clinical outcomes, the minor allele carriers on rs3735451 and the minor allele (A) carriers on rs2246709 were associated with higher incidence of minor bleeding (p = 0.028 and p = 0.038, respectively) and were identified as the independent risk factors of minor bleeding treated with rivaroxaban (p = 0.024 and p = 0.036, respectively), with the receiver operating characteristic (ROC) curve validated (AUC = 0.8956, 95% CI: 0.829-0.962).

CONCLUSION

The CYP3A4 polymorphisms (rs2242480, rs2246709, and rs3735451) and CYP3A5 rs776746 were associated with variations in rivaroxaban PK/PD. The minor allele (C) carriers on rs3735451 and the minor allele (A) carriers on rs2246709 were correlated with clinical outcomes.

Management of patients with proximal femur fractures under DOACs

PURPOSE

In the past, preinjury direct oral anticoagulant (DOAC) intake has led to delays in time to surgery (TTS) in patients with proximal femur fractures and delays in surgery have been associated with impaired outcomes. Although healthcare institutions/federal committees have set rules for treatment within 24 h of injury, comprehensive guidelines for the perioperative management of these patients, in particular when on preinjury DOACs, are still lacking. This contribution aims to summarize the current evidence on the safe time window for surgery in patients with proximal femur fractures on preinjury DOACs and to outline therapeutic options if emergency DOAC reversal becomes necessary.

METHODS

Narrative review based upon selective review of the pertinent literature.

RESULTS

For the majority of patients with proximal femur fractures and on preinjury DOACs, early surgery appears safe as soon as medical clearance has been obtained. There may be an increase in the need for blood products but with data not yet conclusive. Work-up including assessment of remaining anticoagulant activity and potential reversal should be restricted to patients at risk for bleeding complications, in particular in the presence of renal/hepatic impairment. Methodology for rapid assessment of DOACs including quantitative/qualitative concentration levels is work in progress. In the case of bleeding, rapidly acting reversal agents are available.

CONCLUSION

Preinjury DOAC use should not routinely delay surgery in patients with proximal femur fractures.

Calibration-free electrochemical sensor to monitor factor-Xa inhibitors at the point-of-care anticoagulation therapy

This article presents a novel proof of concept for the blood plasma quantification of clinically relevant concentrations of direct oral anticoagulants, DOACs, including rivaroxaban and edoxaban, as well as low-molecular-weight heparins, LMWHs, such as enoxaparin and dalteparin, utilising a calibration-free disposable electrochemical sensor with co-facing electrodes. A dose-response curve was generated for rivaroxaban and edoxaban to demonstrate the sensor's ability to detect ≥9.00 ng mL-1 rivaroxaban and quantify it in the 11.0-140 ng mL-1 range. Similarly, the lower detection limit for edoxaban was 12.9 ng mL-1, with a quantification range of 16.8-140 ng mL-1. The significance of this sensor lies in its ability to quantify rivaroxaban and edoxaban below 30 ng mL-1, which is crucial in emergency care centres when patients undergoing DOAC therapy require emergency surgery or reversal of DOACs due to bleeding or ischemic stroke. Furthermore, the sensor can detect ≥0.016 IU mL-1 enoxaparin and ≥0.013 IU mL-1 dalteparin and quantify them in the 0.025-0.75 and 0.019-0.75 IU mL-1 range, respectively. Additionally, a dose-response curve was presented to demonstrate the potential ability of this sensor to quantify factor-Xa inhibitors independently of which DOACs or LMWHs are used. With the assay completed in less than 30 s using a minimal volume of 7 μL sample, the possibility to work at physiological pH and under calibration-free format makes this assay an excellent candidate for point-of-care testing.

Toward Genetic Testing of Rivaroxaban? Insights from a Systematic Review on the Role of Genetic Polymorphism in Rivaroxaban Therapy

BACKGROUND

Investigations into the rivaroxaban response from the perspective of genetic variation have been relatively recent and wide in scope, whereas there is no consensus on the necessity of genetic testing of rivaroxaban. Thus, this systematic review aims to thoroughly evaluate the relationship between genetic polymorphisms and rivaroxaban outcomes.

METHODS

The PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Chinese databases were searched to 23 October 2022. We included cohort studies reporting the pharmacogenetic correlation of rivaroxaban. Outcomes measured included efficacy (all-cause mortality, thromboembolic events and coagulation-related tests), safety (major bleeding, clinically relevant non-major bleeding [CRNMB] and any hemorrhage), and pharmacokinetic outcomes. A narrative synthesis was performed to summarize findings from individual studies according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and the reporting guideline for Synthesis Without Meta-Analysis.

RESULTS

A total of 12 studies published between 2019 and 2022 involving 1364 patients were included. Ten, one, and six studies focused on the ABCB1, ABCG2, and CYP gene polymorphisms, respectively. Pharmacokinetic outcomes accounted for the majority of the outcomes reported (n = 11), followed by efficacy (n = 5) [including prothrombin time (PT) or international normalized ratio (n = 3), platelet inhibition rate (PIR) or platelet reactivity units (PRUs; n = 1), thromboembolic events (n = 1)], and safety (n = 5) [including major bleeding (n = 2), CRNMB (n = 2), any hemorrhage (n = 1)]. For ABCB1 gene polymorphism, the relationship between PT and ABCB1 rs1045642 was inconsistent across studies, however there was no pharmacogenetic relationship with other efficacy outcomes. Safety associations were found in ABCB1 rs4148738 and major bleeding, ABCB1 rs4148738 and CRNMB, ABCB1 rs1045642 and CRNMB, and ABCB1 rs2032582 and hemorrhage. Pharmacokinetic results were inconsistent among studies. For ABCG2 gene polymorphism, no correlation was observed between ABCG2 rs2231142 and dose-adjusted trough concentration (Cmin/D). For CYP gene polymorphisms, PIR or PRUs have a relationship with CYP2C19 rs12248560, however bleeding or pharmacokinetic effects did not show similar results.

CONCLUSIONS

Currently available data are insufficient to confirm the relationship between clinical or pharmacokinetic outcomes of rivaroxaban and gene polymorphisms. Proactive strategies are advised as a priority in clinical practice rather than detection of SNP genotyping.

CLINICAL TRIALS REGISTRATION

PROSPERO registration number CRD42022347907.

Direct oral anticoagulants or vitamin K antagonists in emergencies: comparison of management in an observational study

Background

Restoring hemostasis in patients on oral anticoagulants presenting with major hemorrhage (MH) or before surgical intervention has changed, with the replacement of vitamin K antagonist (VKA) with direct oral anticoagulants (DOACs).

Objectives

To observe the difference in urgent hemostatic management between patients on VKA and those on DOACs.

Methods

A multicenter observational study evaluated the variation in laboratory testing, hemostatic management, mortality, and hospital length of stay (LOS) in patients on VKA or DOACs presenting with MH or urgent hemostatic restoration.

Results

Of the 1194 patients analyzed, 783 had MH (61% VKA) and 411 required urgent hemostatic restoration before surgery (56% VKA). Compared to the international normalized ratio (97.6%), plasma DOAC levels were measured less frequently (<45%), and the time taken from admission for the coagulation sample to reach the laboratory varied widely (median, 52.3 minutes; IQR, 24.8-206.7). No significant plasma DOAC level (<50 ng/mL) was found in up to 19% of patients. There was a poor relationship between plasma DOAC level and the usage of a hemostatic agent. When compared with patients receiving VKA (96.5%) or dabigatran (93.7%), fewer patients prescribed a factor Xa inhibitor (75.5%) received a prohemostatic reversal agent. The overall 30-day mortality for MH (mean: 17.8%) and length of stay (LOS) (median: 8.7 days) was similar between VKA and DOAC patients.

Conclusion

In DOAC patients, when compared to those receiving VKA, plasma DOAC levels were measured less frequently than the international normalized ratio and had a poor relationship with administering a hemostatic reversal agent. In addition, following MH, mortality and LOS were similar between VKA and DOAC patients.

The myths behind DOAC measurement: Analyses of prescribing information from different regulatory bodies and a call for harmonization

For more than a decade, US laboratories have failed to implement solutions to help their clinicians in managing complex situations or patients on direct oral anticoagulants (DOACs). The problem may find different origins, among which is the position of the Food and Drug Administration, which categorized these drugs as monitoring- and measurement-free, whereas other regulatory bodies like the European Medicines Agency or the Therapeutic Goods Administration in Australia were more conservative on the principle that the absence of proof (of monitoring/measurement benefits) is not proof of an absence (of monitoring/measurement needs). Pivotal clinical studies that led to the approval of DOACs were presented as devoid of such testing, although some companies considered monitoring as a solution to improve their benefit/risk ratio. In this JTH In Clinics issue, we report more than a decade of development that has permitted the activation of smart laboratory solutions to qualify or quantify DOACs and discuss myths and misconceptions around technical and regulatory requirements that support the current reluctance of implementing these technologies in most US laboratories. Use of DOACs is ever expanding, with DOAC prescriptions now exceeding those of other anticoagulants, including vitamin K antagonists, in some geographies. As this use increases, the likely need to measure DOAC exposure will also increase. Measurement of DOACs does not represent any technical difficulty. That these laboratory tests are not available in some locations suggests disparities in patient care, and we suggest it is time to address such inequalities.

Perioperative Management of Direct Oral Anticoagulants in Cardiac Surgery: Practice Recommendations Based on Current Evidence

An increasing number of patients on systemic oral anticoagulants present for cardiac surgery, and cardiac anesthesiologists should be well-informed on their management in the perioperative period. Direct oral anticoagulants (DOACs), including factor Xa inhibitors and direct thrombin inhibitors, are an attractive alternative to warfarin due to fewer dietary and drug interactions, less frequent monitoring requirements, and an improved patient adherence. Since the approval of DOACs by the Food and Drug Administration in 2010, the number of patients on these medications only has increased. The guidelines vary on the periprocedural management of DOACs for cardiac surgery. This review evaluated the current evidence for medication cessation before surgery, based on timing as well as plasma drug concentration. The practice recommendations of various monitoring tests and new evolving point-of-care testing are examined herein. The different reversal agents were discussed by the authors for both elective and urgent procedures. The cardiac anesthesiologist needs to be intimately familiar with the management and current best practices of DOACs for safe and appropriate patient care.

Low Exposure to Direct Oral Anticoagulants Is Associated with Ischemic Stroke and Its Severity

Background and purpose

In acute stroke patients, plasma concentrations of direct oral anticoagulants (DOAC) at hospital admission only poorly mirror DOAC exposure or the coagulation status at the time of the event. Here, we evaluated whether DOAC exposure and DOAC plasma concentration at the time of transient ischemic attacks (TIA) and ischemic strokes correlate with their likelihood of occurrence.

Methods

Prospectively, consecutive DOAC patients with acute ischemic stroke or TIA were included. Admission DOAC plasma concentrations were measured by ultraperformance liquid chromatography– tandem mass spectrometry. Individual DOAC exposure (area under the curve) and DOAC concentrations at event onset were derived from population pharmacokinetic analyses.

Results

DOAC exposure was successfully modeled in 211 patients (ischemic stroke 74.4%, TIA 25.6%). Compared to published values, 63.0% had relatively lower DOAC exposure and they more often received lower DOAC doses than recommended (odds ratio [OR], 2.125; 95% confidence interval [CI], 1.039 to 4.560; P=0.044). These patients more likely suffered ischemic strokes than TIA (OR, 2.411; 95% CI, 1.254 to 4.638; P=0.008) and their strokes were more severe (slope, 3.161; 95% CI, 0.741 to 5.58; P=0.011). Low relative DOAC concentrations at event onset were likewise associated with ischemic strokes (OR, 4.123; 95% CI, 1.834 to 9.268; P=0.001), but not to stroke severity (P=0.272). DOAC exposure had a higher explanatory value for stroke severity than concentrations at event.

Conclusions

Low DOAC exposure is strongly associated to ischemic stroke and its severity. By monitoring DOAC plasma concentrations, patients prone to ischemic stroke might be identified.

Acute Stroke Treatment in an Anticoagulated Patient: When Is Thrombolysis an Option?

Purpose of Review

Direct oral anticoagulants (DOACs: the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban and the direct thrombin inhibitor dabigatran) are the mainstay of stroke prevention in patients with non-valvular atrial fibrillation (AF). Nevertheless, there is a residual stroke risk of 1–2% per year despite DOAC therapy. Intravenous thrombolysis (IVT) reduces morbidity in patients with ischemic stroke and improves functional outcome. Prior DOAC therapy is a (relative) contraindication for IVT but emerging evidence supports its use in selected patients.

Recent Findings

Recent observational studies highlighted that IVT in patients on prior DOAC therapy seems feasible and did not yield major safety issues. Different selection criteria and approaches have been studied including selection by DOAC plasma levels, non-specific coagulation assays, time since last intake, and prior reversal agent use. The optimal selection process is however not clear and most studies comprised few patients.

Summary

IVT in patients taking DOAC is a clinically challenging scenario. Several approaches have been proposed without major safety issues but current evidence is weak. A patient-oriented approach balancing potential benefits of IVT (i.e., amount of salvageable penumbra) against expected bleeding risk including appropriate monitoring of anticoagulant activity seem justified.

MicroRNAs as novel biomarkers for rivaroxaban therapeutic drug monitoring

OBJECTIVES

The aim of this study is to assess micro-RNAs miR-142 and miR-39 as potential biomarkers for drug-monitoring of rivaroxaban among elderly patients with atrial fibrillation.

METHODS

The study involved 57 patients with median (ME) age 87 years [80-94 years old] with nonvalvular atrial fibrillation admitted to a multidisciplinary hospital in Moscow. High-performance liquid chromatography with mass-spectrometry detection (HPLC-MS) was carried out to measure rivaroxaban concentrations. Carriership of CYP3A4 and ABCB1 was detected. MiRNA expression levels were measured. The activity of CYP3A4 isoenzyme was measured as the ratio of the concentrations of 6β-hydroxycortisol and cortisol.

RESULTS

The miR-142 expression levels of patients with CC allelic variant polymorphism ABCB1 3435 C>T (rs1045642) were significantly higher compared to CT and TT variants 31.69 ± 1.60 vs. 34.06 ± 1.66 vs. 33.16 ± 1.77 (p=0.021). Carriers of TT allelic variant polymorphism ABCB1 rs4148738 had a higher concentration of the 6-beta-hydroxycortisol in urine compared to CC and CT variants 3,467.35 ± 1,055.53 vs. 3,453.52 ± 1,516.89 vs. 2,593.30 ± 1,172.52 (p=0.029). As for CYP3A4*22, the carriers of CC allelic variant had higher prothrombin time 14.10 ± 2.17 vs. 11.87 ± 0.60 and INR 1.31 ± 0.20 vs. 1.1 ± 0.06 but lower Quick's value 74.52 ± 16.84 vs. 97.55 ± 10.54 (p=0.059). A positive correlation between the Ct miR-142 and the aPTT p=0.019 was noted. Also miR-142 has a correlation with Quick's value p=0.095. There is no statistically significant connection between miR-142 and miR-39 expression levels and the plasma concentration of rivaroxaban (b coefficient=-2.055, SE 3.952, p=0.605 and b coefficient=1.546, SE 9.887, p=0.876 in the linear regression model respectively).

CONCLUSIONS

This study has assessed new potential biomarkers for rivaroxaban therapeutic drug monitoring: miR-142 and miR-39.

MicroRNAs as novel biomarkers for rivaroxaban therapeutic drug monitoring

OBJECTIVES

The aim of this study is to assess micro-RNAs miR-142 and miR-39 as potential biomarkers for drug-monitoring of rivaroxaban among elderly patients with atrial fibrillation.

METHODS

The study involved 57 patients with median (ME) age 87 years [80-94 years old] with nonvalvular atrial fibrillation admitted to a multidisciplinary hospital in Moscow. High-performance liquid chromatography with mass-spectrometry detection (HPLC-MS) was carried out to measure rivaroxaban concentrations. Carriership of CYP3A4 and ABCB1 was detected. MiRNA expression levels were measured. The activity of CYP3A4 isoenzyme was measured as the ratio of the concentrations of 6β-hydroxycortisol and cortisol.

RESULTS

The miR-142 expression levels of patients with CC allelic variant polymorphism ABCB1 3435 C>T (rs1045642) were significantly higher compared to CT and TT variants 31.69 ± 1.60 vs. 34.06 ± 1.66 vs. 33.16 ± 1.77 (p=0.021). Carriers of TT allelic variant polymorphism ABCB1 rs4148738 had a higher concentration of the 6-beta-hydroxycortisol in urine compared to CC and CT variants 3,467.35 ± 1,055.53 vs. 3,453.52 ± 1,516.89 vs. 2,593.30 ± 1,172.52 (p=0.029). As for CYP3A4*22, the carriers of CC allelic variant had higher prothrombin time 14.10 ± 2.17 vs. 11.87 ± 0.60 and INR 1.31 ± 0.20 vs. 1.1 ± 0.06 but lower Quick's value 74.52 ± 16.84 vs. 97.55 ± 10.54 (p=0.059). A positive correlation between the Ct miR-142 and the aPTT p=0.019 was noted. Also miR-142 has a correlation with Quick's value p=0.095. There is no statistically significant connection between miR-142 and miR-39 expression levels and the plasma concentration of rivaroxaban (b coefficient=-2.055, SE 3.952, p=0.605 and b coefficient=1.546, SE 9.887, p=0.876 in the linear regression model respectively).

CONCLUSIONS

This study has assessed new potential biomarkers for rivaroxaban therapeutic drug monitoring: miR-142 and miR-39.

Point-of-care testing of coagulation in patients treated with edoxaban

Edoxaban, alongside other direct oral anticoagulants (DOAC), is increasingly used for prevention of thromboembolism, including stroke. Despite DOAC therapy, however, annual stroke rate in patients with atrial fibrillation remains 1–2%. Rapid exclusion of relevant anticoagulation is necessary to guide thrombolysis or reversal therapy but, so far, no data exists on the effect of edoxaban on available point-of-care test systems (POCT). To complete our previous investigation on global coagulation-POCT for the detection of DOAC, we evaluated whether CoaguChek®-INR (CC-INR) is capable of safely ruling out edoxaban concentrations above the current treatment thresholds of 30/50 ng/mL in a blood sample. We studied patients receiving a first dose of edoxaban; excluding subjects receiving other anticoagulants. Six blood samples were collected from each patient: before drug intake, 0.5, 1, 2 and 8 h after intake, and at trough (24 h). CC-INR and mass spectrometry for edoxaban concentrations were performed for each time-point. One hundred and twenty blood samples from 20 patients contained 0–302 ng/mL of edoxaban. CC-INR ranged from 0.9 to 2.3. Pearson’s correlation coefficient showed strong correlation between CC-INR and edoxaban concentrations (r = 0.73, p < 0.001). Edoxaban concentrations > 30 and > 50 ng/mL were ruled out by CC-INR ≤ 1.0 and ≤ 1.1, respectively, with high specificity (> 95%), and a sensitivity of 44% (95%-confidence interval: 30–59%) and 86% (74–93%), respectively. Our study represents the first evaluation of coagulation-POCT in edoxaban-treated patients. CC-POCT is suitable to safely exclude clinically relevant edoxaban concentrations prior to thrombolysis, or guide reversal therapy in stroke patients.

Challenges of Acute Ischemic Stroke Treatment in Orally Anticoagulated Patients via Telemedicine

Background: Managing acute ischemic stroke (AIS) in patients receiving treatment with vitamin K antagonists (VKA) or non-VKA oral anticoagulants (NOACs) is difficult and the challenge this poses for stroke telemedicine remains unexplored. Methods: We analyzed data from a random sample (n = 1500) of all teleneurological consultations conducted between July 2015 and December 2017. Management of patients suffering AIS with and without prior oral anticoagulation treatment was characterized, including potential vs. actual treatment with intravenous thrombolysis (IVT) and reasons for withholding it. Results: n = 359 patients had suffered an AIS, of whom 63 (17.5%) were under treatment with oral anticoagulants (VKA, n = 24; NOAC, n = 39). Administration of IVT was more common in patients who had not received prior oral anticoagulation treatment (20.3% vs. 3.2%, p < 0.001). NOAC intake was the primary reason for withholding IVT in 37% of orally anticoagulated patients who were found potentially eligible for IVT. Furthermore, patients under oral anticoagulation tended to be transported to the comprehensive stroke center more often (23.8% vs. 13.9%, p = 0.056). Conclusions: AIS in patients on oral anticoagulation treatment is a frequent reason for telestroke consultation, and NOAC intake constitutes an important barrier to administering IVT.

Recanalisation therapies for acute ischaemic stroke in patients on direct oral anticoagulants

Direct oral anticoagulants (DOACs) have emerged as primary therapeutic option for stroke prevention in patients with atrial fibrillation. However, patients may have ischaemic stroke despite DOAC therapy and there is uncertainty whether those patients can safely receive intravenous thrombolysis or mechanical thrombectomy. In this review, we summarise and discuss current knowledge about different approaches to select patient. Time since last DOAC intake-as a surrogate for anticoagulant activity-is easy to use but limited by interindividual variability of drug pharmacokinetics and long cut-offs (>48 hours). Measuring anticoagulant activity using drug-specific coagulation assays showed promising safety results. Large proportion of patients at low anticoagulant activity seem to be potentially treatable but there remains uncertainty about exact safe cut-off values and limited assay availability. The use of specific reversal agents (ie, idarucizumab or andexanet alfa) prior to thrombolysis is a new emerging option with first data reporting safety but issues including health economics need to be elucidated. Mechanical thrombectomy appears to be safe without any specific selection criteria applied. In patients on DOAC therapy with large vessel occlusion, decision for intravenous thrombolysis should not delay thrombectomy (eg, direct thrombectomy or immediate transfer to a thrombectomy-capable centre recommended). Precision medicine using a tailored approach combining clinicoradiological information (ie, penumbra and vessel status), anticoagulant activity and use of specific reversal agents only if necessary seems a reasonable choice.

Long-Term Anticoagulation in Secondary Ischemic Stroke Prevention: The Prospective Multicenter RESTAIC Registry

Background and Objective: Oral anticoagulation (OAC) for secondary stroke prevention is recommended in atrial fibrillation (AF) and other sources of cardioembolic stroke. Our objectives were to explore the differences in ischemic and hemorrhagic events when using OAC for secondary stroke prevention according to the type of anticoagulant treatment and to analyze the number and reasons for OAC switches during long-term follow-up.

Methods: Ischemic stroke (IS) patients who were discharged on OAC for secondary stroke prevention from January 2014 to October 2017 were recruited in a prospective, multicenter, hospital-based registry. Follow-up at 3 months was scheduled at the outpatient clinic with subsequent annual phone interviews for 3 years. Patients were classified into three study groups according to OAC at discharge: Vitamin K antagonist (VKA), Factor Xa inhibitor (FXa), or direct thrombin inhibitor (DTI). We compared stroke recurrences, intracranial hemorrhage, major bleeding, and all-cause mortality during the follow-up. We recorded any switches in OAC and the main reasons for the change.

Results: A total of 241 patients were included. An anticoagulant was indicated in the presence of a source of cardioembolic stroke in 240 patients (99.6%) and lupus plus antiphospholipid syndrome in one patient. Up to 86 patients (35.6%) were on OAC before the index stroke; in 71 (82.5%) of them, this was VKA. At hospital discharge, 105 were treated with FXa (43.8%), 96 with VKA (39.6%), and 40 with DTI (16.6%). The cumulative incidences at 3 years were 17% for stroke recurrence, 1.6% for intracranial hemorrhage, 4.9% for major hemorrhage, and 22.8% for all-cause mortality, with no differences among the OAC groups in any outcomes. During the follow-up, 40 OAC switches were recorded (63% of them to FXa), mostly due to stroke recurrence.

Conclusion: Long-term OAC in secondary stroke prevention is associated with a lower frequency of bleeding complications than stroke recurrences. No differences between anticoagulant drugs were found in any of the analyzed outcomes. The main cause for OAC switch during follow-up was stroke recurrence.

Prior Anticoagulation in Patients with Ischemic Stroke and Atrial Fibrillation

OBJECTIVE

The aim was to evaluate, in patients with atrial fibrillation (AF) and acute ischemic stroke, the association of prior anticoagulation with vitamin K antagonists (VKAs) or direct oral anticoagulants (DOACs) with stroke severity, utilization of intravenous thrombolysis (IVT), safety of IVT, and 3-month outcomes.

METHODS

This was a cohort study of consecutive patients (2014-2019) on anticoagulation versus those without (controls) with regard to stroke severity, rates of IVT/mechanical thrombectomy, symptomatic intracranial hemorrhage (sICH), and favorable outcome (modified Rankin Scale score 0-2) at 3 months.

RESULTS

Of 8,179 patients (mean [SD] age, 79.8 [9.6] years; 49% women), 1,486 (18%) were on VKA treatment, 1,634 (20%) on DOAC treatment at stroke onset, and 5,059 controls. Stroke severity was lower in patients on DOACs (median National Institutes of Health Stroke Scale 4, [interquartile range 2-11]) compared with VKA (6, [2-14]) and controls (7, [3-15], p < 0.001; quantile regression: β -2.1, 95% confidence interval [CI] -2.6 to -1.7). The IVT rate in potentially eligible patients was significantly lower in patients on VKA (156 of 247 [63%]; adjusted odds ratio [aOR] 0.67; 95% CI 0.50-0.90) and particularly in patients on DOACs (69 of 464 [15%]; aOR 0.06; 95% CI 0.05-0.08) compared with controls (1,544 of 2,504 [74%]). sICH after IVT occurred in 3.6% (2.6-4.7%) of controls, 9 of 195 (4.6%; 1.9-9.2%; aOR 0.93; 95% CI 0.46-1.90) patients on VKA and 2 of 65 (3.1%; 0.4-10.8%, aOR 0.56; 95% CI 0.28-1.12) of those on DOACs. After adjustments for prognostic confounders, DOAC pretreatment was associated with a favorable 3-month outcome (aOR 1.24; 1.01-1.51).

INTERPRETATION

Prior DOAC therapy in patients with AF was associated with decreased admission stroke severity at onset and a remarkably low rate of IVT. Overall, patients on DOAC might have better functional outcome at 3 months. Further research is needed to overcome potential restrictions for IVT in patients taking DOACs. ANN NEUROL 2021;89:42-53.

Monitoring DOACs with a Novel Dielectric Microsensor: A Clinical Study

BACKGROUND

 There are acute settings where assessing the anticoagulant effect of direct oral anticoagulants (DOACs) can be useful. Due to variability among routine coagulation tests, there is an unmet need for an assay that detects DOAC effects within minutes in the laboratory or at the point of care.

METHODS

 We developed a novel dielectric microsensor, termed ClotChip, and previously showed that the time to reach peak permittivity (T _peak) is a sensitive parameter of coagulation function. We conducted a prospective, single-center, pilot study to determine its clinical utility at detecting DOAC anticoagulant effects in whole blood.

RESULTS

 We accrued 154 individuals: 50 healthy volunteers, 49 rivaroxaban patients, 47 apixaban, and 8 dabigatran patients. Blood samples underwent ClotChip measurements and plasma coagulation tests. Control mean T _peak was 428 seconds (95% confidence interval [CI]: 401-455 seconds). For rivaroxaban, mean T _peak was 592 seconds (95% CI: 550-634 seconds). A receiver operating characteristic curve showed that the area under the curve (AUC) predicting rivaroxaban using T _peak was 0.83 (95% CI: 0.75-0.91, p < 0.01). For apixaban, mean T _peak was 594 seconds (95% CI: 548-639 seconds); AUC was 0.82 (95% CI: 0.73-0.91, p < 0.01). For dabigatran, mean T _peak was 894 seconds (95% CI: 701-1,086 seconds); AUC was 1 (p < 0.01). Specificity for all DOACs was 88%; sensitivity ranged from 72 to 100%.

CONCLUSION

 This diagnostic study using samples from "real-world" DOAC patients supports that ClotChip exhibits high sensitivity at detecting DOAC anticoagulant effects in a disposable portable platform, using a miniscule amount of whole blood (<10 µL).

Assessing and Reversing the Effect of Direct Oral Anticoagulants on Coagulation

This article presents a focused review of the available tests to assess the effect of direct oral anticoagulants on coagulation and the use of reversal agents in the perioperative setting for practicing anesthesiologists.

CYP2C19*17 May Increase the Risk of Death Among Patients with an Acute Coronary Syndrome and Non-Valvular Atrial Fibrillation Who Receive Clopidogrel and Rivaroxaban

INTRODUCTION

The aim of this study is to assess the influence of gene CYP2C19, CYP3A4, CYP3A5 and ABCB1 polymorphisms on clopidogrel antiplatelet activity, rivaroxaban concentration equilibrium, and clinical outcomes among patients with acute coronary syndrome and non-valvular atrial fibrillation.

METHODS

In the multicenter prospective registry study of the efficacy and safety of a combined antithrombotic therapy 103 patients with non-valvular atrial fibrillation both undergoing or not a percutaneous coronary intervention were enrolled. The trial assessed the primary outcomes (major bleeding, in-hospital death, cardiovascular death, stroke\transient ischaemic attack, death/renal insufficiency) and secondary outcomes (platelet reactivity units (PRU), rivaroxaban concentration).

RESULTS

For none of the clinical outcomes when combined with other covariates, the carriership of polymorphisms CYP3A5*3 rs776746, CYP2C19*2 rs4244285;*17 rs12248560, ABCB1 3435 C>T, ABCB1 rs4148738 was significant. None of the markers under study (CYP3A5*3 rs776746, CYP2C19*2 rs4244285, *17 rs12248560, ABCB1 3435 C>T, ABCB1 rs4148738) has proven to affect rivaroxaban equilibrium concentration in blood plasma among patients with atrial fibrillation and acute coronary syndrome.

CONCLUSION

In situations of double or triple antithrombotic rivaroxaban and clopidogrel therapy among patients with atrial fibrillation and acute coronary syndrome, the genetic factors associated with bleeding complications risk (CYP2C19*17) may prove to be clinically relevant.

Micellar liquid chromatography determination of rivaroxaban in plasma and urine. Validation and theoretical aspects

A Micellar Chromatographic method to determine rivaroxaban in plasma and urine has been developed. The samples were dissolved in the mobile phase (SDS 0.05 M - 1-propanol 12.5%, phosphate buffered at pH 7) and 20 μL directly injected, avoiding the extraction and purification steps. Using a C18 column and running under isocratic mode at 1 mL/min, analyte was eluted without interference from the matrix in <6.0 min. The detection absorbance wavelength was set to 250 nm. The procedure was validated by Food and Drug Administration guidelines in terms of: system suitability, calibration range (0.05-5 mg/L), linearity, sensitivity, robustness, carry-over effect, specificity, accuracy (-11.1 to 4.2%), precision (<19.9%), stability and analysis of incurred samples. The method was found reliable, practical, easy-to-conduct, rapid, relatively eco-friendly, safe, inexpensive, widely available and with a high sample throughput. The method was applied to the analysis of incurred samples, including incurred sample reanalysis, to verify that the instrumentation works correctly. In addition, the constants of the different partition equilibria occurring in the column were elucidated in order to have a better comprehension of the theoretical aspects of the retention mechanism. A moderately strong association between rivaroxaban and the stationary phase and the micelles was found, weakened by short chain alcohol.

Clinical presentation, diagnostic findings and management of cerebral ischemic events in patients on treatment with non-vitamin K antagonist oral anticoagulants - A systematic review

Background

Non-vitamin K antagonist oral anticoagulants (NOAC) are equally or potentially superior in terms of effectiveness in the prevention of ischemic stroke and carry a lower associated risk of intracranial hemorrhage compared to Vitamin K antagonists. Nevertheless, ischemic strokes also occur in patients who are being treated with NOAC. In those particular patients, knowledge about the underlying stroke etiology, clinical presentation, acute management, and complication rates is scarce.

Objective

Systematic literature review to provide a comprehensive clinical overview in terms of presentation, laboratory, imaging parameters and outcomes of patients suffering from acute cerebral ischemic events (i.e. TIA and acute ischemic stroke) while on treatment with a NOAC. Only if available, comparison to VKA is presented which was not the primary focus of this analysis.

Data sources

PubMed/MEDLINE, Scopus and EMBASE from January 1, 2006, to November 20, 2018.

Study eligibility criteria

52 studies providing detailed information on a total of 12247 patients were included. We excluded case reports and case series with less than five patients.

Study appraisal and synthesis method

We systematically assessed study quality using a bias tool and pooled consistent data.

Results

Existing data indicates milder stroke severity and smaller infarct size of acute ischemic stroke on treatment with NOAC compared to stroke occurrence on Vitamin K antagonists (VKA). Established risk factors for ischemic events also play a role in stroke while on NOACs, albeit the underlying etiology remains poorly understood. Intravenous thrombolysis and endovascular therapy seem to be safe and effective, but patient selection for recanalization therapies is challenging.

Limitations

Limited quality of published data, duplicate cases, statistical issues of data pooling, possible incomplete retrieval of identified research and reporting bias might have limited our findings.

Conclusions

Acute ischemic events despite treatment with NOAC therapy are insufficiently investigated.

Systematic review registration number

PROSPERO: CRD42018074853.

Rivaroxaban plasma levels in patients admitted for bleeding events: insights from a prospective study

Background

Serious bleeding events have been frequently described in patients taking direct oral anticoagulants (DOAC). In secondary analyses of phase 3 trials, DOAC plasma concentrations were shown to correlate with bleeding outcomes. This study aimed to describe rivaroxaban plasma levels in patients admitted to the emergency department (ED) for bleeding events. For each patient, risk factors for experiencing bleeding events were also investigated.

Methods

This analysis was part of an observational study conducted in the ED of two teaching hospitals. Plasma samples from 10 rivaroxaban-treated patients admitted for bleeding events were collected. Rivaroxaban plasma concentrations were determined by calibrated chromogenic anti-Xa assay. The measured rivaroxaban levels were then extrapolated at trough using a published population pharmacokinetic (PopPK) model, and compared to on-therapy ranges observed in large clinical trials. For each patient, clinical, medication and ABCB1 genotype data were collected.

Results

Rivaroxaban measurements varied from 5 to 358 ng/ml, with a post-intake delay ranging from 9 to 38 h. At trough, estimated plasma concentrations were between 12 and 251 ng/ml (median value 94 ng/ml). Four patients had higher-than-expected rivaroxaban levels. Inadequate dose regimen, excessive alcohol consumption and lack of treatment reassessment were observed in several patients. Half of patients were taking ≥1 drug with potential pharmacokinetics interactions (e.g. amiodarone, diltiazem), while half of patients were taking ≥1 drug increasing the risk of bleeding. All 3 patients with available genotyping data and higher-than-expected rivaroxaban levels were heterozygous or homozygous mutated for the ABCB1 1236C > T, 2677G > T, 3435 C > T and rs4148738 single nucleotide polymorphisms (SNP).

Conclusions

Rivaroxaban patients admitted to the ED for bleeding events showed highly variable plasma concentrations. This analysis underlines the usefulness of rapid DOAC measurement and the value of PopPK models to estimate concentrations at trough in a context where the post-intake delay is unmanageable. Close patient follow-up, including renal function assessment and drug interactions review, is essential for bleeding risk minimization.

Testing and monitoring direct oral anticoagulants

Direct oral anticoagulants (DOACs) have significantly improved the care of patients requiring anticoagulation. With similar or better efficacy and safety outcomes and easier use in the outpatient setting compared with the standard-of-care vitamin K antagonists and low molecular weight heparin, DOACs are now endorsed as first-line treatment of indications including prevention of stroke and systemic embolism in nonvalvular atrial fibrillation and treatment of venous thromboembolism. DOACs are easy-to-use oral agents that offer simple dosing and short half-lives, with no need to test levels because of the wide therapeutic window and limited drug-drug interactions. After almost a decade of DOAC use, the question of testing DOAC levels in certain clinical situations has become the focus of debate. Although guidance for using routine coagulation tests is available, these tests are inadequate for optimal care. DOAC-specific tests have been developed but have limited availability in Europe and less availability in the United States. None are licensed. DOAC testing may be useful in the setting of critical clinical situations such as life-threatening bleeding or need for emergent surgery, especially with the availability of DOAC reversal agents. Patients with characteristics that fall outside the normal range may benefit from the guidance that DOAC testing could offer. Obstacles to adopting DOAC testing have been raised, such as test reliability and staffing costs; however, these problems are rapidly being resolved. Further investigation of the role of DOAC testing is needed to explore its full potential and role in clinical practice.

Management of patients with stroke treated with direct oral anticoagulants

Since their market approval, direct oral anticoagulants (DOACs) are being increasingly used for stroke prevention in patients with atrial fibrillation. However, the management of DOAC-treated patients with stroke poses several challenges for physicians in everyday clinical practice, both in the acute setting and in long-term care. This has spurred extensive research activity in the field over the past few years, which we review here.

Rivaroxaban plasma levels in acute ischemic stroke and intracerebral hemorrhage

OBJECTIVE

Information about rivaroxaban plasma level (RivLev) may guide treatment decisions in patients with acute ischemic stroke (AIS) and intracerebral hemorrhage (ICH) taking rivaroxaban.

METHODS

In a multicenter registry-based study (Novel Oral Anticoagulants in Stroke Patients collaboration; ClinicalTrials.gov: NCT02353585) of patients with stroke while taking rivaroxaban, we compared RivLev in patients with AIS and ICH. We determined how many AIS patients had RivLev ≤ 100ng/ml, indicating possible eligibility for thrombolysis, and how many ICH patients had RivLev ≥ 75ng/ml, making them possibly eligible for the use of specific reversal agents. We explored factors associated with RivLev (Spearman correlation, regression models) and studied the sensitivity and specificity of international normalized ratio (INR) thresholds to substitute RivLev using cross tables and receiver operating characteristic curves.

RESULTS

Among 241 patients (median age = 80 years, interquartile range [IQR] = 73-84; median time from onset to admission = 2 hours, IQR = 1-4.5 hours; median RivLev = 89ng/ml, IQR = 31-194), 190 had AIS and 51 had ICH. RivLev was similar in AIS patients (82ng/ml, IQR = 30-202) and ICH patients (102ng/ml, IQR = 51-165; p = 0.24). Trough RivLev_{(≤137ng/ml)} occurred in 126/190 (66.3%) AIS and 34/51 (66.7%) ICH patients. Among AIS patients, 108/190 (56.8%) had RivLev ≤ 100ng/ml. In ICH patients, 33/51 (64.7%) had RivLev ≥ 75ng/ml. RivLev was associated with rivaroxaban dosage, and inversely with renal function and time since last intake (each p < 0.05). INR ≤ 1.0 had a specificity of 98.9% and a sensitivity of 25.7% to predict RivLev ≤ 100ng/ml. INR ≥ 1.4 had a sensitivity of 59.3% and specificity of 90.1% to predict RivLev ≥ 75ng/ml.

INTERPRETATION

RivLev did not differ between patients with AIS and ICH. Half of the patients with AIS under rivaroxaban had a RivLev low enough to consider thrombolysis. In ICH patients, two-thirds had a RivLev high enough to meet the eligibility for the use of a specific reversal agent. INR thresholds perform poorly to inform treatment decisions in individual patients. Ann Neurol 2018;83:451-459.

Laboratory testing in patients treated with direct oral anticoagulants: a practical guide for clinicians

Click to hear Dr Baglin's perspective on the role of the laboratory in treatment with new oral anticoagulants SUMMARY: One of the key benefits of the direct oral anticoagulants (DOACs) is that they do not require routine laboratory monitoring. Nevertheless, assessment of DOAC exposure and anticoagulant effects may become useful in various clinical scenarios. The five approved DOACs (apixaban, betrixaban, dabigatran etexilate, edoxaban and rivaroxaban) have different characteristics impacting assay selection and the interpretation of results. This article provides an updated overview on (i) which test to use (and their advantages and limitations), (ii) when to assay DOAC levels, (iii) how to interpret the results relating to bleeding risk, emergency situations and perioperative management, and (iv) what is the impact of DOACs on routine and specialized coagulation assays. Assays for anti-Xa or anti-IIa activity are the preferred methods when quantitative information is useful, although the situations in which to test for DOAC levels are still debated. Different reagent sensitivities and variabilities in laboratory calibrations impact assay results. International calibration standards for all specific tests for each DOAC are needed to reduce the inter-laboratory variability and allow inter-study comparisons. The impact of the DOACs on hemostasis testing may cause false-positive or false-negative results; however, these can be minimized by using specific assays and collecting blood samples at trough concentrations. Finally, prospective clinical trials are needed to validate the safety and efficacy of proposed laboratory thresholds in relation to clinical decisions. We offer recommendations on the tests to use for measuring DOACs and practical guidance on laboratory testing to help patient management and avoid diagnostic errors.

Detecting clinically relevant rivaroxaban or dabigatran levels by routine coagulation tests or thromboelastography in a cohort of patients with atrial fibrillation

BACKGROUND

Traditional coagulation tests are included in emergency guidelines for management of patients on direct oral anticoagulants (DOACs) who experience acute bleeding or require surgery. We determined the ability of traditional coagulation tests and fast whole blood thromboelastography (ROTEM®) to screen for anticoagulation activity of dabigatran and rivaroxaban as low as 30 ng/mL.

METHODS

One hundred eighty-four citrated blood samples (75 dabigatran, 109 rivaroxaban) were collected from patients with non-valvular atrial fibrillation (NVAF), to perform screening tests from different manufacturers, (diluted, D) PT, aPTT, TT and ROTEM®. The activity of DOACs was quantitatively determined by clot detection assays: Hemoclot DTT and DiXaI test (Biophen), on CS2100 (Siemens). The clotting time (CT) of INTEM and EXTEM ROTEM® (Werfen) were used as test parameters.

RESULTS

Dabigatran, ≥ 30 ng/mL, was accurately detected by five coagulation tests: APTT Actin FSL (93%), PT Neoplastin (93%), APTT Cephascreen, Thromboclotin, and Thrombin (all 100%), but not by PT Innovin (49%). CT-EXTEM (91%) was sufficiently sensitive, but not CT-INTEM (52%). APTT Cephascreen and Thrombin showed good linearity (R2 = 0.71,R2 = 0.72). For the other tests linearity was moderate to poor. Rivaroxaban was accurately detected by PT Neoplastin (98%) and less so by APTT Cephascreen (85%). In addition, rivaroxaban was also accurately detected by CT-INTEM (96%). PT Neoplastin showed good linearity (R2 = 0.81), all other tests had moderate to poor linearity.

CONCLUSION

In patients with NVAF, the ability of routine coagulation tests to detect the presence of significant levels of DOACs is test and reagent dependent. CT-INTEM and CT-EXTEM may be fast whole blood alternatives.

TRIAL REGISTRATION

The Institutional Review Board of the MUMC approved this study (December 2011, project number 114069).

Atherothrombosis and Thromboembolism: Position Paper from the Second Maastricht Consensus Conference on Thrombosis

Atherothrombosis is a leading cause of cardiovascular mortality and long-term morbidity. Platelets and coagulation proteases, interacting with circulating cells and in different vascular beds, modify several complex pathologies including atherosclerosis. In the second Maastricht Consensus Conference on Thrombosis, this theme was addressed by diverse scientists from bench to bedside. All presentations were discussed with audience members and the results of these discussions were incorporated in the final document that presents a state-of-the-art reflection of expert opinions and consensus recommendations regarding the following five topics: 1. Risk factors, biomarkers and plaque instability: In atherothrombosis research, more focus on the contribution of specific risk factors like ectopic fat needs to be considered; definitions of atherothrombosis are important distinguishing different phases of disease, including plaque (in)stability; proteomic and metabolomics data are to be added to genetic information. 2. Circulating cells including platelets and atherothrombosis: Mechanisms of leukocyte and macrophage plasticity, migration, and transformation in murine atherosclerosis need to be considered; disease mechanism-based biomarkers need to be identified; experimental systems are needed that incorporate whole-blood flow to understand how red blood cells influence thrombus formation and stability; knowledge on platelet heterogeneity and priming conditions needs to be translated toward the in vivo situation. 3. Coagulation proteases, fibrin(ogen) and thrombus formation: The role of factor (F) XI in thrombosis including the lower margins of this factor related to safe and effective antithrombotic therapy needs to be established; FXI is a key regulator in linking platelets, thrombin generation, and inflammatory mechanisms in a renin-angiotensin dependent manner; however, the impact on thrombin-dependent PAR signaling needs further study; the fundamental mechanisms in FXIII biology and biochemistry and its impact on thrombus biophysical characteristics need to be explored; the interactions of red cells and fibrin formation and its consequences for thrombus formation and lysis need to be addressed. Platelet-fibrin interactions are pivotal determinants of clot formation and stability with potential therapeutic consequences. 4. Preventive and acute treatment of atherothrombosis and arterial embolism; novel ways and tailoring? The role of protease-activated receptor (PAR)-4 vis à vis PAR-1 as target for antithrombotic therapy merits study; ongoing trials on platelet function test-based antiplatelet therapy adjustment support development of practically feasible tests; risk scores for patients with atrial fibrillation need refinement, taking new biomarkers including coagulation into account; risk scores that consider organ system differences in bleeding may have added value; all forms of oral anticoagulant treatment require better organization, including education and emergency access; laboratory testing still needs rapidly available sensitive tests with short turnaround time. 5. Pleiotropy of coagulation proteases, thrombus resolution and ischaemia-reperfusion: Biobanks specifically for thrombus storage and analysis are needed; further studies on novel modified activated protein C-based agents are required including its cytoprotective properties; new avenues for optimizing treatment of patients with ischaemic stroke are needed, also including novel agents that modify fibrinolytic activity (aimed at plasminogen activator inhibitor-1 and thrombin activatable fibrinolysis inhibitor.

Intravenous Thrombolysis in Patients with Stroke Taking Rivaroxaban Using Drug Specific Plasma Levels: Experience with a Standard Operation Procedure in Clinical Practice

Background and Purpose

Standard operating procedures (SOP) incorporating plasma levels of rivaroxaban might be helpful in selecting patients with acute ischemic stroke taking rivaroxaban suitable for IVthrombolysis (IVT) or endovascular treatment (EVT).

Methods

This was a single-center explorative analysis using data from the Novel-Oral-Anticoagulants-in-Stroke-Patients-registry (clinicaltrials.gov:NCT02353585) including acute stroke patients taking rivaroxaban (September 2012 to November 2016). The SOP included recommendation, consideration, and avoidance of IVT if rivaroxaban plasma levels were <20 ng/mL, 20‒100 ng/mL, and >100 ng/mL, respectively, measured with a calibrated anti-factor Xa assay. Patients with intracranial artery occlusion were recommended IVT+EVT or EVT alone if plasma levels were ≤100 ng/mL or >100 ng/mL, respectively. We evaluated the frequency of IVT/EVT, door-to-needle-time (DNT), and symptomatic intracranial or major extracranial hemorrhage.

Results

Among 114 acute stroke patients taking rivaroxaban, 68 were otherwise eligible for IVT/EVT of whom 63 had plasma levels measured (median age 81 years, median baseline National Institutes of Health Stroke Scale 6). Median rivaroxaban plasma level was 96 ng/mL (inter quartile range [IQR] 18‒259 ng/mL) and time since last intake 11 hours (IQR 4.5‒18.5 hours). Twenty-two patients (35%) received IVT/EVT (IVT n=15, IVT+EVT n=3, EVT n=4) based on SOP. Median DNT was 37 (IQR 30‒60) minutes. None of the 31 patients with plasma levels >100 ng/mL received IVT. Among 14 patients with plasma levels ≤100 ng/mL, the main reason to withhold IVT was minor stroke (n=10). No symptomatic intracranial or major extracranial bleeding occurred after treatment.

Conclusions

Determination of rivaroxaban plasma levels enabled IVT or EVT in one-third of patients taking rivaroxaban who would otherwise be ineligible for acute treatment. The absence of major bleeding in our pilot series justifies future studies of this approach.