Background Altered fibrin clot architecture is a distinct signature in cardiovascular diseases. To determine the origin and importance of these alterations, a fundamental understanding of normal plasma clotting mechanisms is essential. While biochemical and structural aspects of fibrin formation are individually well documented, their mechanistic link lacks a quantitative description. Objectives This study addresses two questions: How does fibrin architecture vary with [TF] in normal plasma, and can a simple mechanistic relationship between fibrin structure and thrombin generation be extracted? Methods The structuring of clots formed in TF-triggered normal pooled plasma and IIa-triggered fibrinogen were compared by varying the triggers concentrations. Architecture was quantified using confocal microscopy (pore size) and fibrinography (nanostructure). Thrombin kinetics were monitored using thrombinography. Results Although purified and plasma clots appeared morphologically identical, their ultrastructural parameters showed fundamentally different sensitivities to trigger concentrations. In purified systems, a 100-fold [IIa] increase induced a 30-fold decrease in protofibril number (Nfinal) and a 5-fold change in pore size. Conversely, plasma clots exhibited remarkable robustness: a 40-fold increase in [TF] resulted in only a 2-fold change in Nfinal, with little pore size evolution. Crucially, by applying inverted purified data to plasma structural data, we predicted thrombin concentrations during the exponential growth phase of plasma CAT curves. Conclusions Our findings show that the unique functional shape of the thrombin burst, rather than the trigger concentration, governs plasma fibrin architecture. This inherent robustness supports the existence of a 'normal' clot structure and the potential of fibrinography as a robust structural biomarker candidate.

Hemophilia is a rare bleeding disorder due to factor VIII (FVIII) or FIX deficiency involved in hemophilia A (HA) or HB, respectively. Treatment has long relied on invasive IV infusions of the missing factor for prophylaxis or bleeding treatments. Despite significant progress in patient care, there is still no oral procoagulant drug available for people with hemophilia. Such an oral procoagulant could provide benefits to other inherited and acquired bleeding disorders, as well as anticoagulant-induced bleeding. To find chemical compounds that could become potential future orally administered procoagulants, we designed a hierarchical high-throughput screening protocol combining 2 successive screening filters: a miniaturized fibrin formation assay, followed by a thrombin generation assay, both on severe HA plasma. We screened 3 chemical collections totaling > 2300 chemical compounds; we identified adapalene, a commercialized antiacneic compound (Differin), which is strongly hydrophobic. To design a drug that could be orally administered, we developed a series of chemical analogs of adapalene, and 3 of them, with similar procoagulant activities in FVIII-deficient plasma, showed improved solubilities. The mechanism of action was thoroughly investigated by a series of thrombin generation and enzymatic assays. These studies conclude that the procoagulant activity of the chemical compounds in FVIII-deficient plasma is due to the activation of FXII.

BACKGROUND:Fibrinogen is the first coagulation factor to drop during severe hemorrhage, making it an early biomarker for assessing bleeding severity. OBJECTIVES:To evaluate the analytical and clinical performance of the Tsmart FIB Batrox©, a novel point-of-care test using batroxobin, a snake venom-derived enzyme insensitive to heparins and direct thrombin inhibitors, performed on the LabPad Evolution analyzer. The assay delivers results in less than 4 min from citrated whole blood, addressing unmet needs in emergency settings. PATIENTS AND METHODS:This study included 121 residual citrated (0.109 mol/L) samples collected for routine coagulation testing. Fibrinogen levels measured by the Tsmart FIB Batrox© assay were compared against the Clauss method (gold standard), performed in the central laboratory using the same samples. RESULTS:The Tsmart FIB Batrox© demonstrated excellent correlation with the Clauss assay (r = 0.94), particularly in the clinically critical range for severe bleeding. Bland-Altman analysis revealed negligible bias. No interference from hematocrit variations or anticoagulants was observed. At fibrinogen cut-offs of 1.0 g/L and 2.0 g/L, it exhibited high diagnostic accuracy (area under the ROC curve values of 0.99 and 0.98, respectively). Precision testing confirmed excellent repeatability and reproducibility, with coefficients of variation <10% across all ranges. CONCLUSION:The Tsmart FIB Batrox© system enables rapid and accurate fibrinogen measurement from a single drop of citrated whole blood, even at the lowest detectable concentrations. Its strong correlation with the Clauss method, high diagnostic accuracy, and POC feasibility make it a valuable tool for real-time decision-making in hemorrhage management.

Exercise may induce platelet activation in spite of using antiplatelet treatment. We present a case where the initial acute coronary syndrome and the iterative stent thrombosis always occurred after intense and prolonged physical effort. For this patient the at rest response to platelet inhibition with antiplatelet treatments was assessed as adequate, but after exercise the patient developed platelet activation which could be the trigger of his stent thrombosis.