Incoprea Theory
Volume V · 2026

Theory 04/Haematology & Coagulation /Haemostasis/3 min

Clots Fail at a Connectivity Threshold

Fibrinogen is measured in grams per litre. The clot may care about how the fibres are wired.

The claim

Clot mechanical stability is set by the connectivity of the fibrin network rather than by fibrinogen concentration, so clots with the same protein content can differ several-fold in strength, and bleeding risk should be predicted from network structure rather than from a concentration assay.

01The evidence

  • The rheology of fibrin clots has been measured as a function of network structure, with dynamic viscoelastic properties and permeation depending on the architecture rather than on protein concentration alone.Biorheology
  • Clot disaggregation studies show that fibrin exposure and susceptibility to lysis change with the arrangement of the network, which is a structural rather than a concentration effect.Arteriosclerosis, Thrombosis, and Vascular Biology

02The tension

Coagulation is monitored with concentration and time assays: fibrinogen, prothrombin time, thromboelastography amplitude. These correlate with bleeding in populations and fail in individuals, and the failures cluster in patients whose fibrinogen is normal but whose clots behave abnormally.

03The theory

A fibrin clot is a network of fibres cross-linked into a mesh. Its resistance to deformation depends on how many load-bearing paths span the clot, which is a connectivity property, not a mass property.

Below a critical connectivity the network is floppy and yields at low stress; above it the clot is stiff. Because connectivity depends on fibre thickness distribution and branching, two clots with identical fibrinogen can sit on opposite sides of the threshold.

The prediction is that strength should scale with a connectivity index, measurable from confocal imaging or from permeation, better than with concentration, and that patients with recurrent bleeding should cluster below the threshold despite normal assays.

The clinical consequence is that a structural assay, which is now feasible with cheap imaging, could replace concentration as the bleeding-risk measure, and that treatments could target fibre architecture rather than bulk fibrinogen.

04What this is not

Concentration-based coagulation assays

Those assays measure how much fibrinogen is present and how fast the clot forms. This measures how the fibrin is connected, which predicts strength differences that concentration cannot.

05Predictions

  • P1Clot strength should correlate with a connectivity index better than with fibrinogen concentration.
  • P2Patients with unexplained bleeding should cluster below a connectivity threshold at normal fibrinogen.
  • P3Treatments altering fibre branching should change strength at constant concentration.

06What would refute it

Strength tracking concentration at fixed architecture would restore the bulk assay.

07What it would change

It would add structural assays to bleeding-risk assessment and change transfusion triggers.

08Evidence base

  1. Rheology of fibrin clots: viscoelastic properties and permeation — Biorheologyhttps://www.sciencedirect.com/science/article/abs/pii/0301462274800025
  2. Fibrin exposure and fibrinolysis in platelet-rich clots — ATVBhttps://www.ahajournals.org/doi/pdf/10.1161/01.atv.21.1.142