Plasma fibrin clots of pulmonary embolism patients present increased amounts of factor XIII and alpha2-antiplasmin at 3 months' anticoagulation since the acute phase.

Fibrin cross-linking by coagulation factor (F)XIII leads to clot stabilization. Reduced plasma FXIII levels have been reported in acute pulmonary embolism (PE) patients. We investigated the impact of anticoagulant therapy on clot-bound amounts of FXIII and α2-antiplasmin and their associations with fibrin clot properties in patients with PE. Clots generated from plasma of 18 acute symptomatic patients on admission and after a 3-month treatment with rivaroxaban were assessed off anticoagulation using mass spectrometry. Plasma FXIII and α2-antiplasmin activity were determined at the 2 time points along with thrombin generation markers, plasma fibrin clot permeability (Ks), and clot lysis time (CLT). Following anticoagulant therapy, clot-bound FXIII increased from 2.97 (interquartile range, 1.98 - 4.08) to 4.66 (3.5 - 6.9) mg/g protein and α2-antiplasmin from 9.4 (7.2 - 10.6) to 11 (9.5 - 14) mg/g protein (both p < 0.0001). The two parameters showed positive correlation at baseline only (r = 0.63, p = 0.0056). Similarly to clot-bound amounts, plasma FXIII (+25.8%) and α2-antiplasmin activity (+12%) increased at 3 months. Plasma FXIII activity on admission, but not after 3 months since the index PE, was associated with amounts of clot-bound FXIII (r = 0.35, p = 0.043) and α2-antiplasmin (r = 0.47, p = 0.048). At baseline, clot-bound FXIII correlated with plasma F1+2 prothrombin fragments levels (r = 0.51, p = 0.03), while clot-bound α2-antiplasmin correlated with CLT (r = 0.43, p = 0.036). At 3 months associations of clot-bound FXIII and α2-antiplasmin were abolished. This study assessed for the first time changes in the fibrin clot composition following acute PE, suggesting an increase of clot-bound and plasma FXIII and α2-antiplasmin levels after 3 months.

Effects of direct oral anticoagulants on thromboelastographic parameters and fibrin clot properties in patients with venous thromboembolism.

Data concerning the impact of direct oral anticoagulants (DOACs) on the thromboelastography (TEG) indices in venousthromboembolism (VTE) patients are limited. The goal of this study was to compare the impact of DOACs on clot properties measured in whole blood using TEG kaolin test and in plasma obtained from real-life VTE patients. We assessed 53 patients, including 20 on rivaroxaban, 20 on apixaban, and 13 on dabigatran. Using the TEG® 5000, coagulation status was evaluated in whole blood samples, while plasma fibrin clot permeability (Ks) and its susceptibility to lysis (CLT) were assessed in citrated plasma. Plasma concentrations of rivaroxaban (99 [48 - 311] ng/ml) and apixaban (85 [40 - 105] ng/ml) were positively associated with Ks and inversely with CLT, while dabigatran concentrations (71 [39 - 98] ng/ml) correlated positively with Ks. Moreover, Ks was associated with clot formation times (R and K), time to maximum clot strength (TMA), coagulation index (CI) reflecting the overall coagulation status, and whole blood clot lysis time (TEG-CLT). Blood clot lysis index (CL30) was associated with plasma CLT in all patients on DOACs, while TMA correlated with CLT only in patients on apixaban. Higher DOAC concentrations were associated with longer retardation of whole blood clot formation and longer time needed to reach maximum level of its strength as well as with more permeable clots. We concluded that plasma fibrin clot properties correlate with corresponding TEG indices suggesting that TEG might be helpful in providing prognostic information about DOAC influence in VTE patients.

Direct oral anticoagulants in patients with antiphospholipid syndrome: a cohort study.

OBJECTIVES: Despite controversies, direct oral anticoagulants (DOACs) are increasingly used in antiphospholipid syndrome (APS). We investigated the safety and efficacy of DOACs versus vitamin K antagonists (VKAs) in real-life consecutive APS patients. PATIENTS AND METHODS: In a cohort study of 176 APS patients, which included 82 subjects who preferred DOACs or had unstable anticoagulation with VKAs, we recorded venous thromboembolism (VTE), cerebrovascular ischemic events or myocardial infarction, along with major bleeding or clinically relevant non-major bleeding (CRNMB). RESULTS: APS patients were followed for a median time of 51 (interquartile range 43-63) months. Patients on DOACs and those on VKAs were similar with regard to baseline characteristics. APS patients treated with DOACs had increased risk of recurrent thromboembolic events and recurrent VTE alone compared with those on VKAs (hazard ratio (HR) = 3.98, 95% confidence interval (CI): 1.54-10.28, p = 0.004 and HR = 3.69, 95% CI: 1.27-10.68, p = 0.016, respectively) with no differences between rivaroxaban and apixaban or single- or double-positive and triple-positive APS. Thromboembolism on DOACs was associated with older age (median 52 versus 42 years, p = 0.008) and higher global APS score (median 13 versus 8.5, p = 0.013). Patients on DOACs had increased risk of major bleeding or CRNMB (HR = 3.63, 95% CI: 1.53-8.63, p = 0.003), but rates of gastrointestinal bleeds (HR = 3.36, 95% CI: 0.70-16.16, p = 0.13) and major bleeds or CRNMB other than heavy menstrual bleeding (HR = 2.45, 95% CI: 0.62-9.69, p = 0.2) were similar in both treatment groups. CONCLUSION: During long-term follow-up of real-life APS patients, DOACs are less effective and less safe as VKAs in the prevention of thromboembolism.

Viscoelastic properties of plasma fibrin clots are similar in patients on rivaroxaban and vitamin K antagonists.

Unfavorable fibrin clot features have been observed in patients with venous thromboembolism (VTE). We investigated whether rivaroxaban, a direct factor Xa inhibitor, and vitamin K antagonists (VKAs) can improve plasma clot viscoelastic properties. We studied four age- and sex-matched groups: 25 healthy controls, 15 VTE patients taking rivaroxaban 20 mg/day (blood concentration, 145 (67 - 217) ng/ml), 15 VTE patients taking VKA (INR: 2 - 3), and 15 VTE patients who stopped oral anticoagulant therapy (OAT). Using a hybrid rheometier the storage (G') and loss (G") moduli were evaluated in citrated plasma after addition of 5 pmol/l tissue factor. Fiber thickness within clots was assessed using scanning electron microscopy. Higher G' but not G" was observed for VTE patients taking rivaroxaban (+34%; post hoc, P = 0.029) compared to controls. As reflected by lower G' and G", patients taking rivaroxaban (-19% and -30%; post hoc, P = 0.0013 and P < 0.0001, respectively) formed less stiff and viscous clots compared to VTE patients after OAT withdrawal, also after adjustment for fibrinogen. VTE patients treated with rivaroxaban and VKA had similar clot viscoelastic properties (post hoc, P = 0.85 for G' and P = 0.29 for G"). G' and G" correlated with plasma rivaroxaban concentrations (r = -0.67, P = 0.005 and r = -0.59, P = 0.021, respectively), and the time from the last dose of rivaroxaban intake (r = 0.59, P = 0.02 and r = 0.58, P = 0.022, respectively). G' and G" showed no association with INR in patients on VKAs. G' or G" were not associated with fibrin diameter on scanning electron microscopy images in either group. Our preliminary study shows that both rivaroxaban and VKA improve clot viscoelastic properties in VTE patients, which might contribute to their antithrombotic effects. G' and G" may reflect specific clot physical features, beyond key plasma clot characteristics, which highlights benefits from comprehensive plasma clot analysis in patients with thrombotic diseases.

Antithrombotic medications and their impact on fibrin clot structure and function.

Fibrin constitutes a major protein component of intravascular thrombi in all locations. Fibrin formation and its functions are essential for physiological hemostasis and the pathologic thrombosis. Formation of dense fibrin networks which are relatively resistant to lysis is observed in patients with venous or arterial thromboembolism, including myocardial infarction, ischemic stroke and venous thromboembolism. Measures of clot characteristics, in particular clot permeability and clot lysis time, may predict arterial and venous recurrent thromboembolic events. Medications, including vitamin K antagonists (VKA), direct oral anticoagulants (DOAC), and parenteral direct or indirect thrombin or activated factor X inhibitors increase clot permeability, reflecting fibrin network density, in association with enhanced efficiency of fibrinolysis. These effects are only in part related to decreased thrombin generation. There is evidence that aspirin can also favorably alter fibrin clot properties probably through acetylation of fibrinogen. No such effects were observed for P2Y12 inhibitors. Of note, plasma fibrin clot permeability has been shown to predict adverse clinical outcomes in patients receiving oral anticoagulants, which might have practical implications. The current review summarizes data on effects of antithrombotic agents on fibrin clot phenotype in cardiovascular disease.

Detection of titanium particles in human liver and spleen and possible health implications.

BACKGROUND: Titanium dioxide (TiO2) is produced at high volumes and applied in many consumer and food products. Recent toxicokinetic modelling indicated the potential of TiO2 to accumulate in human liver and spleen upon daily oral exposure, which is not routinely investigated in chronic animal studies. A health risk from nanosized TiO2 particle consumption could not be excluded then. RESULTS: Here we show the first quantification of both total titanium (Ti) and TiO2 particles in 15 post-mortem human livers and spleens. These low-level analyses were enabled by the use of fully validated (single particle) inductively coupled plasma high resolution mass spectrometry ((sp)ICP-HRMS) detection methods for total Ti and TiO2 particles. The presence of TiO2 in the particles in tissues was confirmed by Scanning Electron Microscopy with energy dispersive X-ray spectrometry. CONCLUSIONS: These results prove that TiO2 particles are present in human liver and spleen, with ≥24% of nanosize (< 100 nm). The levels are below the doses regarded as safe in animals, but half are above the dose that is deemed safe for liver damage in humans when taking into account several commonly applied uncertainty factors. With these new and unique human data, we remain with the conclusion that health risks due to oral exposure to TiO2 cannot be excluded.

Antiphosphatidylserine/prothrombin (aPS/PT) antibodies are associated with Raynaud phenomenon and migraine in primary thrombotic antiphospholipid syndrome.

Objectives Antibodies to phosphatidylserine/prothrombin complex (aPS/PT) detectable in sera of some patients with antiphospholipid syndrome (APS) have been shown to correlate with thrombosis. However, associations of aPS/PT antibodies with APS related disorders remain unclear. Aim To evaluate whether there are any associations between aPS/PT antibodies and Raynaud phenomenon, migraine and/or valvular lesions in primary thrombotic APS (PAPS). Methods We enrolled 67 consecutive patients (56 women) with thrombotic PAPS (VTE in 80.6%), aged 46.2 ± 13.5 years. The exclusion criteria were: acute coronary syndromes or stroke within preceding 6 months, cancer, severe comorbidities and pregnancy. The IgG and IgM aPS/PT antibodies were determined by ELISA with the cut-off of 30 units. We recorded Raynaud phenomenon, migraine and valvular lesions. Results Positive IgM or/and IgG aPS/PT antibodies were observed in 29 patients (43.3%), with a higher prevalence of IgM antibodies ( n = 27, 40.3%) compared with IgG isotype ( n = 12, 17.9%, p = 0.014). aPS/PT antibodies were observed most commonly in patients with triple aPL ( n = 12, 85.7%) compared with those with double ( n = 5, 35.7%) or single aPL antibodies (n = 12, 30.8%, p = 0.03), with no association with demographics, the ANA titre, the type of thrombotic events or medications. Raynaud phenomenon, migraine and valvular lesions were observed in 15% ( n = 10), 30% ( n = 20) and 18% ( n = 12) of the patients, respectively. Raynaud phenomenon and migraine, but not valvular lesions, were markedly more frequent in PAPS patients presenting with positive aPS/PT antibodies ( n = 10, 34.5% vs. n = 0, 0%; p = 0.0001). Conclusions In PAPS patients aPS/PT antibodies are related to the occurrence of both Raynaud phenomenon and migraine.

Factors influencing quality of anticoagulation control and warfarin dosage in patients after aortic valve replacement within the 3 months of follow up.

Warfarin dosage estimation using the pharmacogenetic algorithms has been shown to improve the quality of anticoagulation control in patients with atrial fibrillation. We sought to assess the genetic, demographic and clinical factors that determine the quality of anticoagulation in patients following aortic valve replacement (AVR). We studied 200 consecutive patients (130 men) aged 63 ± 12.3 years, undergoing AVR, in whom warfarin dose was established using a pharmacogenetic algorithm. The quality of anticoagulation within the first 3 months since surgery was expressed as the time of international normalized ratio (INR) in the therapeutic range (TTR). The median TTR in the entire cohort was 59.6% (interquartile range, 38.7 - 82.7). Ninety-nine (49.5%) patients with TTR ≥ 60% did not differ from those with poor anticoagulation control (TTR < 60%) with regard to demographic and cardiovascular risk factors. Coronary artery disease (n = 84, 42%) and previous stroke (n = 5, 2.5%) predicted higher TTR, while possession of CYP2C9*2 variant allele (n = 49, 25%) was associated with lower TTR (P = 0.01). In turn, VKORC1 c.-1639A, CYP2C9*2 and *3 variants were independently associated with actual warfarin dose (P < 0.0001). In AVR patients better anticoagulation control is observed in patients with coronary artery disease and history of stroke, which might result in part from previous lifestyle modification and therapy. Possession of CYP2C9*2 and/or CYP2C9*3 allele variants is associated with lower TTR values and warfarin dose variations in AVR patients, the latter affected also by VKORC1 c.-1693G>A polymorphism.