Viscoelastic Assays: Platelets, Heparin & Hyperfibrinolysis

Current · V5 (2025) → N3.i 1 exam appearance

2026A Q18

Exam question

With respect to viscoelastic assays, describe the expected alterations and the underlying mechanisms resulting from the following:
a) platelet dysfunction (40% of marks),
b) therapeutic heparin use (40% of marks),
c) hyperfibrinolysis (20% of marks). Either TEG or ROTEM is acceptable for your answer.

CICMWrecks answer

Master answer

TEG / ROTEM parameter key

Process	TEG	ROTEM
Clot initiation	R time	CT
Rate of clot formation	K time, α angle	CFT, α angle
Maximum clot strength / firmness	MA	MCF
Clot lysis	LY30 = % amplitude reduction 30 min after MA	LI30 = % clot firmness remaining 30 min after CT; ML = maximum % lysis

Terminology note: TEG and ROTEM use different names for analogous properties: R ≈ CT, K ≈ CFT, and MA ≈ MCF.

Educational diagram comparing ROTEM and TEG mechanics and key viscoelastic parameters, including R or CT, K or CFT, alpha angle, MA or MCF, LY30, LI30 and maximum lysis. — CICMWrecks original (2026)

a) Platelet dysfunction (40%)

TEG / ROTEM feature	Expected change	Mechanism
R / CT	Usually unchanged	Initial fibrin generation is largely preserved because coagulation factor activity is intact.
K / CFT	Prolonged	Impaired platelet–fibrin interaction slows development of a firm clot.
α angle	Reduced	Slower increase in clot strength.
MA / MCF	Reduced	Platelets are a major determinant of maximal clot strength; dysfunction reduces clot firmness.
LY30 / LI30 / ML	Usually no primary fibrinolytic abnormality	Primary abnormality is clot strength, not fibrinolysis.

b) Therapeutic heparin (40%)

Mechanism: heparin potentiates antithrombin, inhibiting thrombin and factor Xa (and other activated serine proteases) → slower fibrin generation and clot propagation.

TEG / ROTEM feature	Expected change	Mechanism
R / CT	Prolonged	Delayed thrombin generation → delayed clot initiation.
K / CFT	Prolonged	Slower fibrin formation delays development of adequate clot strength.
α angle	Reduced	Rate of clot formation is reduced.
MA / MCF	Reduced	Reduced thrombin/fibrin generation produces a less firm clot.
LY30 / LI30 / ML	Usually no primary fibrinolytic abnormality	Heparin impairs coagulation rather than directly accelerating fibrinolysis.

Useful confirmation: correction of the abnormal trace in a heparinase channel supports heparin as the cause.

c) Hyperfibrinolysis (20%)

TEG / ROTEM feature	Expected change	Mechanism
R / CT	Often initially normal	Clot initiation may be preserved.
K / CFT	Often initially near normal	Early clot formation may still occur.
α angle	Often initially near normal	Initial clot propagation may be preserved.
MA / MCF	Initially preserved, then falls	The formed clot is progressively degraded.
LY30	Increased	Greater percentage fall in amplitude measured 30 minutes after MA because fibrinolysis is accelerated.
LI30	Decreased	Lower percentage of clot firmness remains 30 minutes after CT because fibrin is being broken down.
ML	Increased	Greater overall maximum clot lysis.
Trace appearance	Rapid narrowing after peak amplitude	Accelerated plasmin-mediated fibrin breakdown.

One-line comparison

Platelet dysfunction: normal R/CT, weak clot with ↓ MA/MCF and slower clot strengthening.
Heparin: delayed R/CT, slower clot formation (K/CFT prolonged, α reduced) and reduced clot strength.
Hyperfibrinolysis: clot forms, then breaks down too quickly with ↑ LY30 (30 min after MA), ↓ LI30 (30 min after CT), and ↑ ML.

Quick reference

Summary

State	Key TEG / ROTEM pattern
Platelet dysfunction	R/CT preserved; K/CFT prolonged / α reduced; MA/MCF reduced
Heparin	R/CT prolonged; K/CFT prolonged; α reduced; MA/MCF reduced; heparinase correction supports diagnosis
Hyperfibrinolysis	Clot may form initially, then ↑ LY30 (30 min after MA), ↓ LI30 (30 min after CT) and ↑ ML

Past papers

Exam appearances

1 appearance

Exam	Exact exam wording	Candidate success
2026A Q18	With respect to viscoelastic assays, describe the expected alterations and the underlying mechanisms resulting from the following: a) platelet dysfunction (40% of marks), b) therapeutic heparin use (40% of marks), c) hyperfibrinolysis (20% of marks). Either TEG or ROTEM is acceptable for your answer.	29%