High-yield map
Key points before the detail
- 01
Virchow’s triad = endothelial injury/activation, abnormal flow and hypercoagulability.
- 02
Stasis is especially important in venous thrombosis; turbulence and endothelial injury are important in arterial/cardiac thrombosis.
- 03
Thrombi may propagate, embolise, dissolve or organise/recanalise.
- 04
An embolus can be thrombotic or non-thrombotic; the term describes transported intravascular material.
Thrombus versus clot
A thrombus forms within the intact cardiovascular system during life and is attached to a vascular or cardiac surface. A post-mortem or ex-vivo clot forms under different conditions. Histological layering and attachment can help identify antemortem thrombosis, particularly in flowing blood.
Virchow’s triad
| Component | Mechanism | Surgical examples |
|---|---|---|
| Endothelial injury/activation | Exposes or induces procoagulant surfaces and tissue-factor signalling | Atherosclerosis, vascular trauma, intravascular devices |
| Abnormal flow | Stasis prevents dilution/clearance of activated factors; turbulence disrupts laminar flow and can injure endothelium | Immobility, venous obstruction, aneurysm, atrial dilation |
| Hypercoagulability | Inherited or acquired changes favour coagulation over anticoagulant/fibrinolytic control | Malignancy, inflammation, pregnancy, selected inherited thrombophilias |
Arterial and venous emphasis
Arterial thrombi form in high-flow environments and are strongly associated with endothelial injury/atherosclerotic plaque and platelet-rich haemostasis. Venous thrombi form in lower-flow systems where stasis and coagulation-factor activation are prominent; they can extend towards the heart and embolise to the pulmonary circulation. These are tendencies, not absolute biochemical categories.
Fate of a thrombus
- Propagation: continued deposition extends the thrombus.
- Embolisation: part detaches and travels downstream.
- Fibrinolysis: recent thrombus can be broken down, particularly before extensive organisation.
- Organisation: ingrowth of endothelial cells, smooth muscle and fibroblasts converts the thrombus into fibrous tissue.
- Recanalisation: new channels can form through an organised thrombus and partially restore flow.
Embolism is broader than thromboembolism
| Embolic material | Example mechanism |
|---|---|
| Thromboembolus | Detached venous, arterial or cardiac thrombus |
| Fat/marrow | Can enter the circulation after major long-bone or soft-tissue injury |
| Gas | Air entry or decompression-related gas bubbles |
| Atheromatous debris | Cholesterol-rich material released from atherosclerotic plaque |
Active recall
Close the notes and answer these
Try each question from memory before revealing the answer. These public prompts are a small preview of the integrated retrieval system inside SurgAtlas.
01What are the three parts of Virchow’s triad?
Endothelial injury/activation, abnormal blood flow, and hypercoagulability.
02What can happen to a thrombus over time?
It can propagate, embolise, undergo fibrinolysis, organise and sometimes recanalise.
03Does embolus always mean thrombus?
No. An embolus is transported intravascular material and may be thrombotic, fat/marrow, gas or other material.
Sources & editorial basis
References & editorial basis
- SurgAtlas production chapter — Atherosclerosis, Thrombosis and Embolism. Primary source for this public lesson. The public teaching is a condensed, source-derived version of the corresponding production pathology chapter.
- Robbins & Cotran Pathologic Basis of Disease. Reference for stable thrombosis and embolism pathology.
This lesson is derived from the corresponding SurgAtlas production teaching material. Where the source makes current management or guideline claims, the public lesson uses the cited contemporary guidance. It is written for education and examination preparation, not as patient-specific clinical advice.
Editorial details
Medical Doctor (MD) · MRCS Part A · Physician · Surgical Educator
SurgAtlas is an educational resource. For patient care, verify current national guidance, local antimicrobial and transfusion policies, specialty pathways and individual patient factors.
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