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.

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.

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.

Blood coagulation and fibrinolysis in aortic valve stenosis: links with inflammation and calcification.

Aortic valve stenosis (AS) increasingly afflicts our aging population. However, the pathobiology of the disease is still poorly understood and there is no effective pharmacotherapy for treating those at risk for clinical progression. The progression of AS involves complex inflammatory and fibroproliferative processes that resemble to some extent atherosclerosis. Accumulating evidence indicates that several coagulation proteins and its inhibitors, including tissue factor, tissue factor pathway inhibitor, prothrombin, factor XIII, von Willebrand factor, display increased expression within aortic stenotic valves, predominantly on macrophages and myofibroblasts around calcified areas. Systemic impaired fibrinolysis, along with increased plasma and valvular expression of plasminogen activator inhibitor-1, has also been observed in patients with AS in association with the severity of the disease. There is an extensive cross-talk between inflammation and coagulation in stenotic valve tissue which contributes to the calcification and mineralisation of the aortic valve leaflets. This review summarises the available data on blood coagulation and fibrinolysis in AS with the emphasis on their interactions with inflammation and calcification.

Impaired fibrinolysis is associated with the severity of aortic stenosis in humans.

BACKGROUND: A role of fibrinolysis in the pathogenesis of aortic valve stenosis (AS) is unknown, although fibrinolytic proteins have been detected in aortic stenotic valves. OBJECTIVE: To investigate whether impaired fibrinolysis could be associated with AS. METHODS AND RESULTS: We studied 74 patients with AS (43 male, 31 female, aged 62.7 ± 10.7 years) without documented atherosclerotic valvular disease scheduled for isolated valve replacement and 68 controls. The plasma fibrin clot lysis time (CLT) in the presence of tissue factor (TF) and tissue plasminogen activator (tPA), along with plasma plasminogen activator inhibitor-1 (PAI-1) were determined. Valvular expression of fibrin and PAI-1 together with macrophages and mast cells (MC) was evaluated by immunostaining. Patients with AS compared with controls were characterized by a prolonged CLT (median, 110 [54-153] vs. 92.5 [58-115] min, P = 0.0007) and increased plasma PAI-1 (78.6 [35.5-149] vs. 38.5 [18-61] ng mL(-1) , P < 0.0001). CLT was correlated with maximal (r = 0.43, P = 0.0002) and mean (r = 0.38, P = 0.001) transvalvular pressure gradients, and aortic valve area (r = -0.59, P < 0.0001). In AS patients, the CLT was positively correlated with the valve leaflet thickness (r = 0.67, P = 0.003), the degree of valve calcification (r = 0.65, P < 0.00001), valvular fibrin (r = 0.54, P = 0.007) and PAI-1 expression (r = 0.48, P = 0.007). Double-immunostaining revealed colocalization of valvular PAI-1 with MC (87 ± 17% cells) and macrophages (48 ± 11% cells) within stenotic valves. CONCLUSIONS: Hypofibrinolysis might be a marker of severe AS and be implicated in AS progression.

Mast cells in human stenotic aortic valves are associated with the severity of stenosis.

Aortic valve stenosis (AS) is characterized by extensive calcification of the aortic valve leaflets and infiltration of inflammatory cells. Activated mast cells (MCs) may participate in the induction of fibrosis and calcification with ensuing valve stiffening. We sought to investigate whether the number of MCs within stenotic aortic valves is associated with the severity of AS. We studied 43 patients (19 men, 24 women) with dominant AS (age, 64.2 ± 5.9 years; mean transvalvular pressure gradient, 62.11 ± 24.47 mmHg) without atherosclerotic vascular disease, undergoing elective aortic valve replacement. MCs were detected in the excised valves by immunostaining. Aortic valves from five healthy subjects obtained on autopsy served as negative controls. The number of tryptase- and chymase-positive MCs was increased in AS valves compared with the control valves (6.9 [2.3-18.9]/mm(2) vs. 0.7 [0-2.2]/mm(2), P = 0.0001 and 3.2 [2.1-9.4]/mm(2) vs. 0.3 [0-1.9]/mm(2), P = 0.002, respectively). MCs that colocalized with macrophages and neovessels were detected mainly in the calcified regions of the leaflets. The number of MCs positively correlated with maximal (r = 0.73, P < 0.0001) and mean (r = 0.78, P < 0.0001) gradients and maximal aortic jet velocity (r = 0.68, P = 0.0005). An inverse correlation with aortic valve area (r = -0.71, P = 0.0001) was also observed. Multivariate regression analysis revealed that MC number and valve thickness were significantly associated with mean transvalvular gradient (R (2) = 0.74, P < 0.000001) in AS patients. Increased MC number within human stenotic aortic valves is associated with the severity of AS.