Pathology · Year 2 · from Pathology

Case 1: Pulmonary Embolism - Thromboembolism

Patient Demographics

• Age: 52 years old
• Sex: Female
• Occupation: Accountant (sedentary work)

Chief Complaint

"Sudden shortness of breath and sharp chest pain that started this morning"

History of Present Illness

A 52-year-old woman presents to the emergency department with sudden-onset dyspnea and right-sided pleuritic chest pain that began 3 hours ago while she was at work. She describes the pain as sharp, worsening with deep inspiration, and rates it 7/10. She also noticed her heart racing and felt lightheaded. She returned from a 12-hour flight from Australia 5 days ago and has been relatively sedentary since due to jet lag. She takes oral contraceptive pills for menorrhagia. Her BMI is 32. She denies hemoptysis, leg pain, or swelling. Family history is notable for a sister who had a blood clot during pregnancy.

Physical Examination

• Vital Signs: BP 100/70 mmHg, HR 118 bpm, RR 28/min, Temp 37.4°C (99.3°F), SpO2 88% on room air
• General: Anxious-appearing woman in moderate respiratory distress
• Cardiovascular: Tachycardic, regular rhythm, loud P2, no murmurs, JVP elevated
• Lungs: Clear to auscultation bilaterally (no infiltrates)
• Extremities: Right calf mildly swollen (2 cm difference), positive Homans sign (calf pain with dorsiflexion)

Diagnostic Workup

Laboratory Studies:

Imaging:

• CT Pulmonary Angiogram: Large saddle embolus at main pulmonary artery bifurcation with extension into bilateral pulmonary arteries. Right ventricle dilated with RV/LV ratio >1.0 (right heart strain)
• Doppler Ultrasound of Legs: Non-compressible right popliteal and femoral veins consistent with deep vein thrombosis

ECG: Sinus tachycardia, S1Q3T3 pattern, right axis deviation

Echocardiogram: Dilated right ventricle with reduced RV function, interventricular septum bowing into left ventricle, McConnell's sign (RV free wall hypokinesis with apical sparing)

Pathology Correlation

This case demonstrates thromboembolism and Virchow's triad:

1. Virchow's Triad (Risk Factors Present):

• Stasis: Long-haul flight, sedentary lifestyle
• Endothelial injury: Oral contraceptives, possible inherited thrombophilia
• Hypercoagulability: Oral contraceptives, family history suggesting inherited condition

1. Deep Vein Thrombosis Formation:

• Thrombus originated in deep leg veins
• Venous thrombi are "red thrombi" (rich in RBCs, fibrin)
• Propagated proximally in lower extremity veins

1. Embolization:

• Thrombus dislodged and traveled through IVC to right heart
• Lodged at pulmonary artery bifurcation (saddle embolus)
• Mechanical obstruction of pulmonary blood flow

1. Pathophysiology of Symptoms:

• Hypoxemia: V/Q mismatch from non-perfused lung segments
• Right heart strain: Increased pulmonary vascular resistance
• Elevated D-dimer: Fibrinolysis of thrombus
• Elevated troponin/BNP: RV myocardial strain

Clinical Image

CT pulmonary angiogram demonstrating a saddle pulmonary embolism. The thrombus (dark filling defect) straddles the bifurcation of the main pulmonary artery and extends into both right and left pulmonary arteries. This pattern of massive PE causes significant hemodynamic compromise due to obstruction of pulmonary blood flow.

Image Source: Wikimedia Commons - "Saddle Pulmonary Embolism" License: CC BY-SA 3.0 URL: https://commons.wikimedia.org/wiki/File:Saddle_pulmonary_embolism.png

Diagnosis

Massive Pulmonary Embolism with hemodynamic compromise (intermediate-high risk) secondary to proximal DVT

Treatment

1. High-flow oxygen therapy
2. IV heparin anticoagulation (unfractionated heparin given hemodynamic instability)
3. ICU admission for monitoring
4. Consider catheter-directed thrombolysis or systemic thrombolysis if deterioration
5. Transition to oral anticoagulation (DOAC) once stable
6. Minimum 3 months anticoagulation; consider extended therapy
7. Thrombophilia workup after acute treatment
8. IVC filter only if anticoagulation contraindicated

Teaching Points

1. Virchow's triad (stasis, endothelial injury, hypercoagulability) describes conditions predisposing to thrombosis
2. Venous thrombi are red, RBC-rich, and arise in areas of stasis
3. 95% of pulmonary emboli originate from deep leg veins
4. D-dimer has high sensitivity but low specificity; useful to rule out PE if low
5. Right ventricular strain (elevated troponin, dilated RV) indicates intermediate-high risk PE
6. Saddle embolus straddles the main pulmonary artery bifurcation and indicates massive PE
7. Oral contraceptives increase thrombotic risk 3-4 fold, especially in combination with other risk factors

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