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Questions and Answers
What is the primary goal of hemostasis?
What is the term for the formation of a blood clot within non-traumatized, intact vessels?
What is the result of endothelial injury in the context of thrombosis?
What is the term for the 'Virchow triad'?
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What is the result of a thrombus breaking off and traveling to another part of the body?
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What is the term for the morphological changes that occur as a result of thrombosis?
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What is the most common source of pulmonary embolism?
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Where do most systemic emboli come to rest?
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What is the term for gas bubbles in the circulation that can cause distal ischemic injury?
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What is the characteristic of infarctions caused by venous thrombosis?
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What is the dominant histology of infarcts?
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What is the outcome of pulmonary embolism?
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What is the term for the passage of an embolus through an interatrial or interventricular defect?
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What is the characteristic of red infarcts?
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What is the outcome of fat and marrow embolism?
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What is the term for the formation of thrombi in the microcirculation?
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What type of blood flow contributes to the development of venous thrombi?
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What is the purpose of the slower-moving layer of plasma in normal blood flow?
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What is the primary cause of hypercoagulability?
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What is the result of a point mutation in the prothrombin gene?
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What is a secondary cause of hypercoagulability?
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What is an example of a condition that increases the risk of DVT?
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Study Notes
Thrombosis and Embolism
- Hypercoagulability states can lead to thrombosis and embolism, including:
- Hyperestrogenic states (pregnancy and postpartum)
- Oral contraceptive use
- Sickle cell anemia
- Smoking
- Thrombus morphology:
- Lines of Zahn: alternating pale platelet and fibrin layers with darker red cell-rich layers
- Fate of the thrombus:
- Propagation: enlargement
- Embolization: transported elsewhere
- Dissolution: fibrinolysis
- Organization and recanalization: ingrowth of endothelial cells, smooth muscle cells, and fibroblasts
Clinical Features
- Venous thrombosis (phlebothrombosis):
- Most common in superficial or deep veins of legs
- Deep vein thrombosis (DVT): causes localize pain and edema; associated with stasis or hypercoagulable state
- Arterial and cardiac thrombosis:
- Atherosclerosis, myocardial infarction, and rheumatic heart disease can lead to thrombosis, which can embolize to brain, kidneys, and spleen
- Disseminated intravascular coagulation (DIC):
- Pathologic activation of coagulation cascade, leading to widespread thrombi formation in microcirculation
- Consumptive coagulopathy: uses up platelets and coagulation factors, which can evolve into bleeding catastrophe
- Secondary to obstetric complications, advanced malignancy, or sepsis
Embolism
- An embolus is a detached intravascular solid, liquid, or gaseous mass that travels through the blood to a distant site, causing tissue dysfunction or infarction
- Emboli can travel through the bloodstream until they encounter vessels too small to permit further passage, causing partial or complete vascular occlusion
Pulmonary Embolism
- Originate from deep venous thromboses and are the most common form of thromboembolic lesions
- Can occlude the main pulmonary artery, lodge at the pulmonary artery bifurcation (saddle embolus), or pass out into smaller branching arteries
- Rarely, a venous embolus can pass through an interatrial or interventricular defect and gain access to the systemic arterial circulation (paradoxical embolism)
Systemic Thromboembolism
- Mostly arise from intracardiac mural thrombi
- Most commonly involve the lower extremities (75%) or brain (10%)
- Consequences depend on the vulnerability of the affected tissues to ischemia, the caliber of the occluded vessel, and the presence of collateral blood supply
Fat and Marrow Embolism
- Microscopic fat globules and hematopoietic bone marrow can be found in the pulmonary vasculature after fractures of long bones or soft tissue trauma
Air Embolism
- Gas bubbles within the circulation can coalesce to form frothy masses that obstruct vascular flow and cause distal ischemic injury
- Decompression sickness: nitrogen dissolved in the blood and tissues during high-pressure breathing (e.g., scuba diving) can come out of solution during rapid decompression, causing gas bubbles to form
Infarction
- Ischemic necrosis caused by occlusion of either the arterial supply or venous drainage
- Arterial thrombosis or arterial embolism underlies the vast majority of infarctions
- Venous thrombosis most commonly leads to congestion
- Infarcts caused by venous thrombosis are more likely in organs with a single efferent vein (e.g., testis and ovary)
Morphology of Infarction
- Red (hemorrhagic) or white (anemic) and may be septic or bland
- Red infarcts: occur with venous occlusions (e.g., testicular or ovarian torsion) or in tissues with dual circulations (e.g., lung and small intestine)
- White infarcts: occur with arterial occlusions in solid organs with end-arterial circulation (e.g., heart, spleen, and kidney)
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Description
This quiz covers the causes and morphology of thrombosis, including hypercoagulability, pulmonary embolism, and the structure of thrombi. Topics include hyperestrogenic states, sickle cell anemia, and oral contraceptive use.
