Apixaban concentration variability and relation to clinical outcomes in real-life patients with atrial fibrillation.

In some clinical situations, measurements of anticoagulant effect of apixaban may be needed. We investigated the inter- and intra-individual apixaban variability in patients with atrial fibrillation and correlated these results with clinical outcome. We included 62 patients receiving either 5 mg (A5, n = 32) or 2.5 mg (A2.5, n = 30) apixaban twice-daily. We collected three trough and three peak blood samples 6-8 weeks apart. Apixaban concentration was measured by liquid chromatography-tandem mass-spectrometry (LC-MS/MS) and by anti-Xa. Patients on A2.5 were older, had lower creatinine clearance, higher CHA2DS2VASc (4.7 ± 1.0 vs. 3.4 ± 1.7) and lower trough (85 ± 39 vs. 117 ± 53 ng/mL) and peak (170 ± 56 vs. 256 ± 91 ng/mL) apixaban concentrations than patients on A5 (all p < 0.01). In patients on A5, LC-MS/MS showed a significant difference between through levels and between peak levels (p < 0.01). During apixaban treatment, 21 patients suffered bleeding (2 major). There was no association between bleeding and apixaban concentrations or variability. Four patients who suffered thromboembolic event had lower peak apixaban concentrations than patients without it (159 ± 13 vs. 238 ± 88 ng/mL, p = 0.05). We concluded, that there was a significant intra- and inter-individual variability in apixaban trough and peak concentrations. Neither variability nor apixaban concentrations were associated with clinical outcomes.

The in vitro addition of idarucizumab to plasma samples from patients increases thrombin generation.

Dabigatran interferes with many coagulation tests. To overcome this obstacle the use of idarucizumab as an in vitro antidote to dabigatran has been proposed. The aim of this study was to test the effect of idarucizumab as an in vitro antidote to dabigatran in ex vivo plasma samples from routine clinical patients examined by a thrombin generation assay (TGA). From 44 patients with atrial fibrillation five blood samples were collected. Thrombin generation was measured in all samples before and after the addition of idarucizumab. When idarucizumab was added to baseline plasma (no dabigatran), it caused a significantly shorter Lag Time and Time to Peak Thrombin, and a higher Peak Thrombin and Endogenous Thrombin Potential (ETP) of TGA. Similar results were obtained when idarucizumab was added to dabigatran-containing plasma, with TGA parameters comparable to baseline + idarucizumab plasma, but not to baseline plasma. In summary, our study showed that in vitro addition of idarucizumab to plasma samples from patients increases thrombin generation. The use of idarucizumab to neutralize dabigatran in patient plasma samples as well as the clinical relevance of in vitro increased thrombin generation induced by idarucizumab needs further investigation.

Idarucizumab for dabigatran reversal in daily clinical practice: A case series.

BACKGROUND: Real-life experience with idarucizumab, which reverses the anticoagulant effect of dabigatran, is currently limited. OBJECTIVE: To evaluate efficacy and safety of the clinical use of idarucizumab after its availability in Slovenia. METHODS: We analysed consecutive cases treated with idarucizumab in Slovenia from January to October 2016. The decision to reverse dabigatran with idarucizumab was made by the treating clinicians, as was the assessment of clinical outcomes and blood sampling/monitoring (activated partial thromboplastin time, thrombin time and diluted thrombin time) before and after use. RESULTS: Idarucizumab was used in 17 cases. One patient was treated with the antidote twice with an interval of 2 months between treatments. The indications for idarucizumab use were: emergency surgery (4/17), severe bleeding (11/17; seven with intracranial bleeding) and ischaemic stroke (2/17). During surgery, no excessive bleeding was reported. Five patients died due to cardiogenic, haemorrhagic or septic shock, intracranial bleeding or multiple organ failure. Among cases with laboratory data available, baseline coagulation tests were prolonged in 12/13 cases with bleeding or emergency surgery. After idarucizumab administration, normal coagulation parameters were confirmed in 10/11. However, re-occurrence of dabigatran effect was noted later in four patients with creatinine clearance less than 30 ml min, and one patient with persistent bleeding required retreatment with idarucizumab. CONCLUSION: Our first experiences with idarucizumab use in daily-care settings support a rapid and efficient decrease in the anticoagulant effect of dabigatran in emergency situations. Late re-occurrence of dabigatran effect was noted in a subset of patients with severe renal failure.

Risk of major bleeding in elderly patients with atrial fibrillation on direct oral anticoagulants: real world experience.

Background The efficacy and safety of direct oral anticoagulants is well established in patients with atrial fibrillation. However, data on their use in the oldest old patients (≥ 85 years), who have the highest risk of bleeding, is scarce. Objective The aim of this study was to evaluate the safety of direct oral anticoagulants in the oldest old patients with atrial fibrillation and assess the impact of age on major bleeding events. Setting Anticoagulation Clinic of the Department of Vascular Diseases, University Medical Centre Ljubljana, Slovenia. Methods From our single-centre prospective registry we enrolled 2260 consecutive atrial fibrillation patients aged ≥ 65 years that were started on dabigatran, rivaroxaban or apixaban. The mean duration of treatment exposure was 735 days. The primary outcome was the incidence of major bleeding. The incidence of thromboembolic events and death were also assessed. Potential risk factors for major bleeding were evaluated using Cox regression analysis. Main outcome measure Rate of major bleeding. Results During the follow-up 106 patients experienced major bleeding (2.3%/year). The oldest old patients (≥ 85 years) had the highest risk of any major bleeding (HR 2.50, 95% CI 1.44-4.32, p = 0.001), intracranial bleeding (HR 4.74, 95% CI 1.48-15.14, p < 0.01) and major gastrointestinal bleeding (HR 2.32, 95% CI 1.10-4.89, p < 0.03) compared to the group of patients aged 65-74 years, even though the majority of them were treated with reduced doses of direct oral anticoagulants. Significant predictors for major bleeding were age group ≥ 85 years (HR 2.52, 95% CI 1.43-4.47, p = 0.001) and history of bleeding (HR 3.32, 95% CI 1.87-5.90, p < 0.001). The incidence of a composite of stroke, transient ischemic attack and systemic embolism was 1.3%/year. Conclusion In this prospective real-world clinical study we have shown that the oldest old patients have the highest risk of major bleeding, which is further increased with a patient's history of bleeding.

Intra- and inter- individual rivaroxaban concentrations and potential bleeding risk in patients with atrial fibrillation.

BACKGROUND: Routine laboratory monitoring of rivaroxaban and dose adjustment relating to exposure is currently not recommended. However, in certain clinical situations, assessment of rivaroxaban levels is desirable. OBJECTIVES: To examine inter- and intra-subject plasma rivaroxaban variability in patients with atrial fibrillation (AF) and to correlate these results to clinical outcomes. PATIENTS/METHODS: We included 60 patients with AF treated with rivaroxaban: half on 20 mg daily (R20) and half on 15 mg daily (R15). Three trough and peak blood samples were collected with an interval of 6-8 weeks apart. Plasma rivaroxaban concentration was measured directly by liquid chromatography-tandem mass-spectrometry (LC-MS/MS) and indirectly by anti-Xa for rivaroxaban, prothrombin time (PT), and activated partial thromboplastin time (APTT). RESULTS: Patients on R15 were older (76 ± 6 vs 71 ± 6 years), had lower creatinine clearance (60 ± 26 vs 99 ± 32 mL/min), higher CHADS2 (2.5 ± 1.2 vs 1.8 ± 1.3), all p < 0.01, but had similar rivaroxaban concentrations in trough samples to patients on R20. There was no significant intra-individual variability for trough or peak rivaroxaban concentration assessed by LC-MS/MS, anti-Xa, or PT. Trough rivaroxaban levels determined by LC-MS/MS (48 ± 30 vs 34 ± 26, p = 0.02) and anti-Xa, but not with PT and APTT, were higher in patients with bleeding than in patients without it. CONCLUSIONS: There is a pronounced inter-, but not intra-individual variability in the rivaroxaban trough levels in patients with AF. Assessment of trough rivaroxaban concentration with LC-MS/MS or anti-Xa, but not with APTT or PT, may help to identify patients at increased risk of bleeding.

Impact of Asymptomatic Pulmonary Embolism on the Long-Term Prognosis of Patients with Deep Venous Thrombosis.

Asymptomatic pulmonary embolism (PE) is present in at least one-third of patients with deep venous thrombosis (DVT). However, knowledge about its influence on the prognosis of patients is limited. The aim of this study was to assess the prognostic impact of asymptomatic PE in patients with DVT and to explore risk factors for recurrent venous thromboembolic events. A total of 200 consecutive patients with the first episode of objectively confirmed DVT without symptoms of PE were included. All patients underwent ventilation-perfusion scintigraphy within 48 hours of DVT confirmation. Patients with inconclusive scans further underwent computed tomography pulmonary angiography. At the time of inclusion and 4 weeks after discontinuation of anticoagulation, the levels of biomarkers of hemostasis and inflammation were assessed. Patients were followed up for a mean period of 4.2 ± 0.6 years. Recurrent episodes of venous thromboembolisms were recorded. Consistent with the literature, asymptomatic PE was present in 33.5% of the patients. During follow-up, 27 recurrent venous thromboembolisms were recorded, 20 presenting as DVT and 7 as symptomatic PE. Asymptomatic PE wasn't significantly associated with the rate of recurrence (p = 0.676). Recurrent events were associated with unprovoked versus provoked DVT (hazard ratio [HR]: 5.01; 95% confidence interval [CI]: 2.25-11.17; p < 0.001) and with increased versus normal D-dimer values, measured 4 weeks after discontinuation of anticoagulation (HR: 6.47; 95% CI: 2.96-14.17; p < 0.001).

Risk of Thromboembolic Events in Patients with Non-Valvular Atrial Fibrillation After Dabigatran or Rivaroxaban Discontinuation - Data from the Ljubljana Registry.

BACKGROUND AND AIM: Interruption of anticoagulant treatment with warfarin or non-vitamin K antagonist oral anticoagulants (NOAC) represents a vulnerable period with an increased risk of thromboembolic events. What is the incidence of thromboembolic events in real-life patients with non-valvular atrial fibrillation treated with NOAC who had a discontinuation or cessation of treatment in comparison to patients on continuous treatment? PATIENTS AND METHODS: Registry data from 866 patients with non-valvular atrial fibrillation, aged 74.3 (SD 9.8) years, with an average CHADS2 score of 2.1 (SD 1.2), who were started on dabigatran or rivaroxaban, were analysed for thromboembolic events and survival. Patients who had temporary or permanent discontinuation of NOAC were compared to patients on continuous NOAC treatment. RESULTS: Among 866 patients started on NOAC, 705 were treated without interruption, 84 patients had temporary interruption (69 because of planned invasive procedures, 10 due to bleeding, 5 for other causes) and 77 had permanent cessation of NOAC treatment. In patients without interruptions, the incidence of thromboembolic events was 1.0 (95% CI 0.4-2.1) per 100 patient-years, while in patients with interruption/cessation the rate of thromboembolic events was 21.6 (95% CI 10.3-45.2) per 100 patient-years, p < 0.001. There was a distinct clustering of thromboembolic events in the first weeks of NOAC discontinuation with the median occurring on day 14 (range 1-37 days) after discontinuation. CONCLUSION: Dabigatran and rivaroxaban offered good protection against thromboembolic events during treatment, but interruption of NOAC treatment increased the short-term thromboembolic risk more than 20-fold.

Diluted thrombin time reliably measures low to intermediate plasma dabigatran concentrations.

BACKGROUND: Direct oral anticoagulant dabigatran was first introduced as a fixed-dose drug without routine coagulation monitoring, but current recommendations suggest that diluted thrombin time can be used to estimate plasma drug level. The aim of this study was to assess a diluted thrombin time assay based on the same thrombin reagent already used for traditional thrombin time measurements that reliably measure low to intermediate plasma dabigatran levels. METHODS: We included 44 patients with atrial fibrillation who started treatment with dabigatran 150 mg (23 patients) or 110 mg (21 patients) twice a day. Blood samples were collected at baseline (no dabigatran) and 2-4 weeks after the beginning of dabigatran therapy at trough and at peak. Plasma dabigatran levels were measured with diluted thrombin time and compared to liquid chromatography with tandem mass spectrometry as the reference method. The performance of the diluted thrombin time was compared to Hemoclot® Thrombin Inhibitor and Ecarin Chromogenic Assay. RESULTS: In ex vivo plasma samples, diluted thrombin time highly correlated with the liquid chromatography with tandem mass spectrometry (Pearson's R = 0.9799). In the low to intermediate range (dabigatran concentration ≤ 100 µg/L) diluted thrombin time correlated significantly more closely to the liquid chromatography with tandem mass spectrometry (R = 0.964) than Hemoclot® Thrombin Inhibitor (R = 0.935, p = 0.05) or Ecarin Chromogenic Assay (R = 0.915, p < 0.01). It was also the only functional assay without any significant bias in the low to intermediate range. Both trough and peak diluted thrombin time values were similar to liquid chromatography with tandem mass spectrometry. CONCLUSION: We conclude that the diluted thrombin time assay presented in this study reliably detects dabigatran and that it is superior to the Hemoclot® Thrombin Inhibitor assay in the low to intermediate range.

Dabigatran Concentration: Variability and Potential Bleeding Prediction In "Real-Life" Patients With Atrial Fibrillation.

Routine laboratory monitoring is currently not recommended in patients receiving dabigatran despite its considerable variation in plasma concentration. However, in certain clinical situations, measurements of the dabigatran effect may be desirable. We aimed to assess the variability of dabigatran trough and peak concentration and explore the potential relationship between dabigatran concentration and adverse events. We included 44 patients with atrial fibrillation who started treatment with dabigatran 150 mg (D150) or 110 mg (D110) twice daily. They contributed 170 trough and peak blood samples that were collected 2-4 and 6-8 weeks after dabigatran initiation. Plasma dabigatran concentration was measured by LC-MS/MS and indirectly, by selected coagulation tests. D110 patients were older (74 ± 7 versus 68 ± 6 years), had lower creatinine clearance (68 ± 21 versus 92 ± 24 mL/min) and higher CHA2 DS2 -VASc score (3.1 ± 1.3 versus 2.3 ± 0.9) compared to D150 patients (all p < 0.05), but both had similar dabigatran concentrations in both trough and peak samples. Dabigatran concentrations varied less in trough than in peak samples (17.0 ± 13.6 versus 26.6 ± 19.2%, p = 0.02). During the 12-month follow-up, 4 patients on D150 and 6 on D110 suffered minor bleeding. There was no major bleeding or thromboembolic event. Patients with bleeding had significantly higher average trough dabigatran concentrations (93 ± 36 versus 72 ± 62 µg/L, p = 0.02) than patients without bleeding, while peak dabigatran values had no predictive value. Dabigatran dose selection according to the guidelines resulted in appropriate trough concentrations with acceptable repeatability. High trough concentrations may predispose patients to the risk of minor bleeding.

Unprovoked proximal venous thrombosis is associated with an increased risk of asymptomatic pulmonary embolism.

INTRODUCTION: Pulmonary embolism (PE) is common in patients with deep venous thrombosis (DVT). The outcome of DVT with concomitant symptomatic PE is worse than the outcome of isolated DVT. The risk factors for DVT and simultaneous asymptomatic PE have not been systematically studied yet. AIM: To evaluate the frequency and risk factors for asymptomatic PE in patients with DVT. PATIENTS/METHODS: In 155 consecutive patients with a first episode of DVT and no PE symptoms, a ventilation-perfusion lung scan was performed. Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated and concentrations of D-dimer, high-sensitivity CRP (hsCRP), tissue plasminogen activator (t-PA) and troponin were measured. Laboratory tests for thrombophilia were performed. RESULTS: Asymptomatic PE was present in 36% of patients. No differences in gender, age, BMI and WHR were found between the patients with and without PE. PE was more common in patients with proximal DVT than in those with distal DVT (42% vs. 17%, p<0.01), and in patients with unprovoked DVT compared to patients with provoked DVT (51% vs. 28%, p<0.01). The risk of silent PE was the highest in patients with unprovoked proximal DVT (OR, 6.9; 95% CI, 2.3-21.0). Patients with asymptomatic PE had significantly higher values of D-dimer, hsCRP, t-PA and troponin than patients with isolated DVT. CONCLUSIONS: Asymptomatic PE affected more than one third of patients with a first DVT. Unprovoked proximal DVT is the most important risk factor for the occurrence of silent PE.

Procoagulant state in heart failure with preserved left ventricular ejection fraction.

The impact of heart failure with preserved left ventricular ejection fraction (LVEF) on activated hemostasis is still unclear. We sought to compare the activation of hemostasis in patients with heart failure with preserved LVEF, with impaired LVEF, and in healthy controls. Biomarkers of coagulation and fibrinolysis (D-dimer, tPA and PAI-1) were determined in outpatients with chronic stable (NYHA I-III), optimally managed heart failure with preserved LVEF (n = 46) and with impaired LVEF (n = 52), and in healthy age- and gender-matched controls (n = 14). In comparison to healthy controls, patients with heart failure and preserved LVEF had increased median D-dimer levels (606 [330-1222] microg/L versus 174 [86-249] microg/L; P < 0.001), and median PAI-1 (20 [15.3-33.1] microg versus 6.2[3.4-8.9] microg/L; P < 0.001) and tPA antigen concentrations (9.6 [8.1-13.3] versus 3.6 [2.2-5.0] microg/L; P < 0.001). However, unlike tPA and PAI antigens, D-dimer levels in preserved LVEF did not reach values as high as in impaired LVEF (917 [454-1185] microg/L; P = 0.013). Moreover, in patients with impaired LVEF, but not in those with preserved LVEF, age and NT-proBNP emerged as independent predictors of log-transformed D-dimer levels. Heart failure with preserved LVEF is associated with a procoagulant state as determined by increased levels of D-dimer, tPA and PAI-1 antigens. D-dimer levels are significantly higher in patients with impaired LVEF, while tPA and PAI-1 levels are increased regardless of LVEF.

Prognostic impact of haemostatic derangements in chronic heart failure.

Heart failure is characterised by activation of haemostasis. We sought to explore the prognostic impact of deranged haemostasis in chronic heart failure. In stable, optimally managed outpatients with chronic heart failure, baseline levels of prothrombin fragment F1+2, D-dimer, and tPA and PAI-1 antigens were determined. Clinical follow-up was obtained and the rate of events (heart failure related deaths or hospitalisations) was recorded. We included 195 patients [32.3% female, NYHA class II (66.2%) or III (33.8%), mean age 71 years]. During a median follow up of 693 (interquartile range [IQR] 574-788) days, 63 (30.9%) patients experienced an event; those with an event had higher levels of tPA antigen (median 11.8 [IQR 8.7-14.0] vs. 9.4 [7.9-12.1] microg/l; p = 0.033) and D-dimer (938 [485-1269] vs. 620 [37-1076] microg/l; p = 0.018). However, on Cox multivariate analysis, only tPA levels above optimal cut-off value of 10.2 microg/l (but not D-dimer) emerged as an independent predictor of prognosis (HR(adjusted) 2.695, 95% confidence interval 1.233-5.363; p = 0.017). Our findings suggest that elevated tPA antigen levels are an independent prognostic predictor in patients with chronic stable heart failure.

Interleukin-6 is a stronger prognostic predictor than high-sensitive C-reactive protein in patients with chronic stable heart failure.

Heart failure is characterized by activation of the immune system which is strongly associated with disease severity and outcome. We sought to compare the prognostic impact of two established inflammatory markers - interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) - in patients with chronic heart failure. In stable, optimally managed outpatients with chronic heart failure, baseline levels of hsCRP and IL-6 were determined. Clinical follow-up was obtained and the rate of events (heart failure related deaths or hospitalizations) were recorded. We included 201 patients (32.7% female, NYHA class II [66.2%] or III [33.8%], mean age 70 years). During a median follow up of 614 (367-761) days, 64 (30.9%) patients experienced an event; those with an event had higher levels of hsCRP (median 2.93 [interquartile range 2.36-8.92] vs 2.23 [1.32-5.77] mmol/l) and IL-6 (7.8 [4.7-10.3] vs 4.3 [2.6-7.9] pg/ml). However, on Cox multivariate analysis, IL-6 but not hsCRP emerged as an independent predictor of prognosis (hazard ratio HR(adjusted) 2.74, 95% confidence interval 1.17-6.43; P = 0.020). Our findings suggest that IL-6 is a better prognostic predictor than hsCRP in patients with chronic stable heart failure.

High D-dimer levels predict cardiovascular events in patients with chronic atrial fibrillation during oral anticoagulant therapy.

Atrial fibrillation (AF) is associated with hemostatic abnormalities and increased risk of thrombotic cardiovascular events even during oral anticoagulant therapy (OAT). The aim of our study was to evaluate the predictive value of hemostatic markers for the risk of major cardiovascular events during OAT. The study group comprised 113 patients with chronic AF (70.2 +/- 5.4 years old, 60% men), referred for OAT. Established clinical risk factors and levels of prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complexes (TAT), D-dimer, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) antigen and activity, before and during OAT (after 3.9 +/- 0.7 months; INR 2.57 +/- 0.57) were determined. In all patients OAT significantly suppressed levels of F1+2 by 67%,TAT by 30% and D-dimer by 48% (all p <0.001). During an average follow-up of 44 months 22/111 (20%) patients suffered a combined cardiovascular event (stroke, myocardial infarction, peripheral vascular occlusion or vascular death). Patients with cardiovascular events were significantly older, had more frequent heart failure/systolic dysfunction and had significantly increased levels of D-dimer at entry (63 vs 39 ng/mL, p = 0.005) and during OAT (33 vs 18 ng/mL, p = 0.002), and of t-PA antigen at entry (14.3 vs 10.9 ng/mL, p = 0.02) and during OAT (15.0 vs 11.2 ng/mL, p = 0.05) (all values are medians). In multivariate Cox proportional hazard models, heart failure/systolic dysfunction (hazard ratio 2.91; 95% CI 1.17-7.26; p = 0.02), high levels of D-dimer on OAT (top vs. lower two quartiles) (hazard ratio 4.78, 95% CI 1.39-16.41; p = 0.01) and t-PA antigen levels (continuous variable) (hazard ratio 1.09; 95% CI 1.01-1.17; p = 0.02) were significantly associated with combined cardiovascular events. In conclusion, high levels of D-dimer and t-PA antigen during OAT are significant predictors of combined cardiovascular events in AF patients and, on this basis, could be useful additional markers of cardiovascular risk in such patients.

Do haemostasis activation markers that predict cardiovascular disease exist?

Recognition of the central role of thrombosis in the pathogenesis of cardiovascular disease has prompted growing interest in the association of haemostatic variables with cardiovascular disease. In investigating the predictive value of haemostasis markers, a promising type of measurement is that of the activation products of coagulation and fibrinolysis: prothrombin fragment 1+2 (F1+2), fibrinopeptide A (FPA), soluble fibrin,thrombin-antithrombin (TAT), plasmin-antiplasmin(PAP) complexes and D-dimer. D-dimer was most extensively studied and there is substantial evidence that D-dimer is a strong, consistent predictor of cardiovascular events in the general population and inpatients with cardiovascular disease. Data on other markers are considerably less abundant and more controversial. The prognostic value of these markers remains to be fully defined in future epidemiological and clinical studies.