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Questions and Answers
What are the primary abnormalities that lead to thrombus formation?
What are the primary abnormalities that lead to thrombus formation?
In which of the following locations is venous thrombus development most commonly associated?
In which of the following locations is venous thrombus development most commonly associated?
What is the likely outcome of a large pulmonary embolus that blocks a major pulmonary artery?
What is the likely outcome of a large pulmonary embolus that blocks a major pulmonary artery?
Which type of vein is primarily associated with superficial venous thrombi?
Which type of vein is primarily associated with superficial venous thrombi?
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What is the significance of turbulence in relation to thrombus formation?
What is the significance of turbulence in relation to thrombus formation?
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What percentage of patients with venous thrombosis are typically asymptomatic?
What percentage of patients with venous thrombosis are typically asymptomatic?
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Which of the following statements is true regarding the coagulation cascade?
Which of the following statements is true regarding the coagulation cascade?
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What can occur as a consequence of multiple pulmonary emboli over time?
What can occur as a consequence of multiple pulmonary emboli over time?
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Which artery is most commonly affected by saddle emboli?
Which artery is most commonly affected by saddle emboli?
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What underlying condition is primarily linked to primary (inherited) hypercoagulability?
What underlying condition is primarily linked to primary (inherited) hypercoagulability?
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Study Notes
Hemodynamic Disorders
- Hemodynamics describes blood flow, pressure, and volume
- Hemostasis maintains blood in a fluid, clot-free state in normal vessels while forming a clot at injury sites.
- Thrombosis is the formation of a clot (thrombus) in intact blood vessels, the pathological counterpart of hemostasis.
- Three key elements in thrombus formation are the vascular wall, platelets, and the coagulation cascade.
Thrombosis
- Virchow's triad describes the primary abnormalities causing thrombus formation: endothelial injury, stasis or turbulent blood flow, and hypercoagulability of the blood.
Endothelial Injury
- Examples include cardiac chambers after myocardial infarction, areas over ulcerated atherosclerotic plaques, and sites of traumatic or inflammatory vascular injury (vasculitis).
Abnormal Blood Flow
- Turbulence leads to arterial and cardiac thrombosis due to endothelial damage
- Stasis is a key factor in venous thrombi formation.
Hypercoagulability
- An important underlying risk factor for venous thrombosis.
- Primary hypercoagulability (inherited) is common in young patients (<50 years) and involves mutations in the factor V Leiden and prothrombin genes.
- Other less common causes include inherited deficiencies of anticoagulants like antithrombin III, protein C, or protein S.
- Secondary hypercoagulability (acquired) is related to factors like oral contraceptives and pregnancy (hyperestrogenic state), disseminated cancers (releasing procoagulant tumor products like mucin from adenocarcinomas), advancing age (partially related to aspirin), and smoking or obesity.
Types of Thrombi by Location
- Mural thrombi occur in heart chambers.
- Venous thrombi (phlebothrombosis) frequently develop in lower leg veins (90% of cases).
Special Cases
- Antiphospholipid antibody syndrome features recurrent thrombosis, repeated miscarriages, cardiac valve vegetations, and thrombocytopenia.
- This syndrome is linked to autoantibodies targeting anionic phospholipids (e.g., cardiolipin) or plasma proteins (e.g., prothrombin).
- A secondary syndrome arises from pre-existing autoimmune diseases like systemic lupus erythematosus. A primary form exists without other autoimmune markers.
Embolism
- An embolus is a solid, liquid, or gaseous mass (carried by blood) that lodges at a distant site.
- The vast majority originate from dislodged thrombi (thromboembolism).
- Less common causes include fat droplets, air or nitrogen, atherosclerotic debris, tumor fragments, bone marrow bits, and amniotic fluid.
Thromboembolism
- Thrombi can obstruct arteries and veins, potentially forming emboli.
- Venous thrombi are most concerning due to potential lung embolisation and death.
- Arterial embolisation to coronary or cerebral vessels are critical.
Deep Venous Thromboses ("DVTs")
- Commonly involve larger leg veins above the knee (popliteal, femoral, iliac).
- DVTs are serious and prone to embolization.
- A significant proportion of patients are asymptomatic until embolization to the lungs.
Venous Thrombosis (Phlebothrombosis)
- Can occur in both superficial and deep leg veins.
- Superficial thrombi often involve saphenous and varicose veins; are less likely to embolize.
Pulmonary Thromboembolism
- Most cases arise from thrombi in deep leg veins above the knee.
- Pulmonary embolism (PE) size dictates location (main artery, bifurcation, or smaller branch arterioles).
- Recurrence is a concern.
Clinical Features of Pulmonary Embolism
- Most PE are small and asymptomatic.
- Large emboli can cause sudden death from major artery blockage or rupture of capillaries (leading to bleeding).
- Embolism to smaller pulmonary branches results in infarction.
- Multiple emboli can lead to pulmonary hypertension and right ventricular failure (cor pulmonale).
Systemic Thromboembolism
- Most (80%) systemic emboli arise from intracardiac mural thrombi (often related to left ventricular infarcts or dilated left atria).
- Other causes include aortic aneurysms and thrombi on ulcerated atherosclerotic plaques.
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Description
Explore the critical concepts of hemodynamics, hemostasis, and thrombosis in this quiz. Understand the factors contributing to thrombus formation and the significance of Virchow's triad. Test your knowledge about endothelial injury and abnormal blood flow as key elements in clot formation.
