Ryan 10/13/25

Patient Presentation

• A woman visits health student health services at UT campus.

• Chief complaint: leg pain.

  • Duration: 1 day.

  • No reported injury or extreme exertion.

  • Patient has been seated for 4 days, working on her thesis.

• Medical History:

  • No past medical history reported.

  • Outpatient medications:

  • Oral contraceptives.

  • Multivitamins.

Coagulation Disorders

• Problem scope:

  • Up to 2 million cases of thromboembolism (DVT, pulmonary embolism) annually in the US.

  • Around 100,000 deaths per year attributed to thromboembolisms.

• Pathways to thromboembolic events:

  • Genetic predisposition: inherited disorder, genetic anomalies.

  • Acquired conditions contributing to clot formation.

• Importance: High morbidity and mortality rates in hospitalized patients and those in outpatient care.

Coagulation System Overview

• Function of the coagulation system:

  • Maintain balance between clot formation and breakdown to prevent excessive bleeding or abnormal clotting.

• Activation triggers:

  • Vessel injury (physical or toxic).

• Activation Process:

  • Immediate response to injury:

  • Vessel spasms and platelet activation.

  • Platelets aggregate (become sticky, change shape, activate other platelets).

  • Fibrin clot formation: Critical for controlling bleeding.

Key Factors in Coagulation Pathway

• Focus on important factors rather than memorizing the entire pathway.

• Factor Xa:

  • Generated by tissue factor from extrinsic and intrinsic pathways.

  • Cleaves prothrombin to thrombin (factor II), ultimately leading to fibrin clot formation.

• Feedback mechanisms:

  • Antithrombin III: Inactivates factors II, IX, and Xa.

  • Thrombin: Activates protein C to provide feedback inhibition to slow down coagulation.

  • Protein C and S: Inactivate factors V and VIII to prevent excessive clotting.

Clot Composition

• Components of a thrombus:

  • Red blood cells, white blood cells, platelets, fibrin (threads holding components together).

• Clinical Importance:

  • Large thrombus can occlude vessels, resulting in decreased blood flow (perfusion issues).

• Definitions:

  • Embolus: A dislodged thrombus carried via blood flow.

  • Example: Thrombus in leg can travel to lungs, causing pulmonary embolism; thrombus in heart can travel to the brain, causing stroke.

Virchow's Triad and Risk Factors for Thrombus Formation

• Virchow's Triad:

  • Circulatory stasis.

  • Hypercoagulable state.

  • Endothelial injury.

• Conditions leading to risk:

  • Immobilization (e.g., post-surgery).

  • Atrial fibrillation (AFib) leading to abnormal blood flow.

  • Heart failure resulting in decreased cardiac output.

Hypercoagulable States

• Definitions: Refers to conditions increasing risk of clot formation.

• Genetic risk factors include:

  • Antithrombin III deficiency (impaired clot breakdown).

  • Protein C deficiency (disrupted feedback loop).

  • Elevated levels of factors VIII, XI, and homocysteine.

  • Activated protein C resistance (most common genetic condition).

• Acquired risk factors include:

  • Age (increased risk with age).

  • Immobilization (e.g., prolonged bed rest).

  • Pregnancy, hormonal therapies (oral contraceptives).

  • Obesity and diabetes (both increase inflammatory states).

  • Certain cancers associated with thromboembolic risks.

Risk Factors in the Case of the Patient

• Identified risk factors for leg pain:

  • Oral contraceptives (estrogen present).

  • Prolonged sitting (immobilization for 4 days).

Thrombosis Sites

• Common sites for venous thrombi:

  • Femoral vein, popliteal vein (behind the knee), saphenous veins, lesser saphenous vein, smaller calf veins.

• Clinical symptoms of DVT (Deep Vein Thrombosis):

  • Non-specific signs: swelling, redness, pain, edema (also indicative of other conditions).

  • Specific phenomena: palpable cord on examination, tenderness indicated by Homan's sign (dorsiflexion pain).

Wells Criteria for DVT Evaluation

• Pretest probability assessment tool for DVT:

  • Assign points based on risk factors (cancer, immobilization, prior DVT).

  • Points:

  • 0 or less: low probability for clot.

  • 1-2: moderate probability.

  • Greater than 3: high probability.

Diagnostic Testing for Possible DVT

• D-dimer assay:

  • A measure of fibrin breakdown; highly sensitive test.

  • Negative result provides definitive exclusion of DVT; positive result requires further imaging.

• Imaging techniques:

  • Venous ultrasound (most common, non-invasive).

  • Venography (gold standard but rarely used due to invasiveness).

Case Review: Next Steps for the Patient

• For the patient:

  • D-dimer test initial step, potentially followed by ultrasound for confirmation of DVT.

Pulmonary Embolism (PE) Overview

• Definition: Dislodged thrombus caught in pulmonary vasculature; can cause impaired perfusion in lungs.

• Symptoms of PE:

  • Dyspnea, pleuritic chest pain, potentially hemoptysis (rare).

  • Clinical suspicion criteria similar to Wells criteria for DVT.

Diagnostic Workup for PE

• Initial tests may include D-dimer to rule out PE.

  • Positive results lead to advanced imaging.

• Imaging modalities include:

  • Pulmonary angiography (gold standard, invasive).

  • Ventilation-perfusion (VQ) scan.

  • Spiral CT (common practice).

Treatment Goals for Thromboembolic Disorders

• Overall patient goals:

  • Reduce morbidity/mortality, improve quality of life.

  • Prevent clot formation and embolization.

• Treatment Approaches:

  • Anticoagulation therapy.

  • Consider thrombectomy or fibrinolysis for massive PE causing right ventricular strain.

  • Use of IVC filters for high-risk patients unable to anticoagulate.

• Management for patients with mechanical valves to minimize thromboembolic risks.

Conclusion

• Importance of understanding coagulation disorders, risk factors, and treatment options for effective patient care.