Pulmonology · Venous Thromboembolism
The facts most likely to be tested
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The most common symptom of a pulmonary embolism is sudden-onset dyspnea, while the most common physical exam finding is tachypnea.
The Wells Criteria is the standard clinical decision rule used to determine the pretest probability of a pulmonary embolism.
A D-dimer test is highly sensitive and is used to rule out pulmonary embolism in patients with low pretest probability.
CT pulmonary angiography (CTPA) is the gold standard diagnostic imaging modality for patients with suspected pulmonary embolism.
Ventilation-perfusion (V/Q) scan is the preferred diagnostic test for patients with renal insufficiency or contrast allergy who cannot undergo CTPA.
Hemodynamically unstable patients presenting with hypotension or obstructive shock require immediate thrombolytic therapy (e.g., alteplase) if there are no absolute contraindications.
Right ventricular strain on echocardiogram (e.g., McConnell sign) is a marker of submassive pulmonary embolism and indicates a higher risk of decompensation.
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A 58-year-old female presents to the emergency department with acute-onset shortness of breath and pleuritic chest pain that began two hours ago. She recently returned from a 12-hour international flight. On physical exam, she is tachycardic (115 bpm), tachypneic (24 breaths/min), and has an O2 saturation of 91% on room air. Her right calf is swollen and tender to palpation. A bedside echocardiogram reveals right ventricular dilation and hypokinesis.
What is the most appropriate next step in the management of this patient?
CT pulmonary angiography (CTPA)
The patient has a high pretest probability for pulmonary embolism based on the Wells criteria; CTPA is the gold standard diagnostic test to confirm the diagnosis in hemodynamically stable patients.
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Etiology / Epidemiology
Most arise from deep vein thrombosis (DVT) in the lower extremities. Key risks include Virchow's triad: stasis, hypercoagulability, and endothelial injury.
Clinical Manifestations
Sudden onset dyspnea and pleuritic chest pain. Look for Hampton's hump or Westermark sign on CXR.
Diagnosis
The CT pulmonary angiography (CTPA) is the gold standard. Use Wells criteria to determine pre-test probability.
Treatment
Hemodynamically stable patients receive anticoagulation (e.g., DOACs). Unstable patients require thrombolysis.
Prognosis
Massive PE carries a >50% mortality rate if untreated. Monitor for right ventricular strain.
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Epidemiology & Etiology
PE is a major cause of preventable hospital death. Primary risk factors include recent surgery, malignancy, immobilization, and oral contraceptive use. Genetic predispositions like Factor V Leiden must be considered in recurrent cases.
Pertinent Anatomy
Thrombi typically originate in the popliteal, femoral, or iliac veins. Emboli travel through the right heart to lodge in the pulmonary arterial tree, causing ventilation-perfusion (V/Q) mismatch.
Pathophysiology
Obstruction leads to increased pulmonary vascular resistance and acute right ventricular (RV) afterload. This causes RV dilation, septal bowing, and decreased left ventricular filling. The resulting hypoxemia is driven by dead-space ventilation and intrapulmonary shunting.
Clinical Manifestations
Patients present with tachycardia, tachypnea, and hypoxia. S1Q3T3 pattern on ECG is rare but specific. Syncope or hypotension indicates massive PE and hemodynamic collapse.
Diagnosis
Calculate Wells criteria first; if low probability, use D-dimer to rule out. CT pulmonary angiography is the diagnostic test of choice. If renal failure prevents contrast, use V/Q scan.
Treatment
Start heparin or LMWH immediately if clinical suspicion is high. Transition to apixaban or rivaroxaban for long-term therapy. Thrombolytics (e.g., tPA) are reserved for patients with hemodynamic instability.
Prognosis
Assess severity using the PESI score. Complications include chronic thromboembolic pulmonary hypertension (CTEPH). Follow-up imaging is required for patients with persistent symptoms.
Differential Diagnosis
Acute MI: ST-segment elevation on ECG
Pneumothorax: absent breath sounds on affected side
Aortic dissection: tearing chest pain radiating to the back
Pneumonia: fever and productive cough
Pericarditis: positional chest pain relieved by leaning forward