Pulmonary Embolism

History

Symptoms of the PE itself include:

• sudden onset shortness of breath
• chest pain that may be pleuritic
• hemoptysis

Risk factors for DVT include:

• stasis: immobilization, obesity, CHF, chronic venous insufficiency
• endothelial damage: post-operative, trauma
• hypercoagulability: smoking, oral contraception, cancer, pregnancy, post-partum, nephrotic syndrome, coaglulopathy, family history, prior DVT

signs or symptoms of DVT

immobility

hypercoagulability

medications: oral contraceptives

Physical Exam

Vital signs

• severe hypoxemia
• hypotension
• tachycardia
• tachypnea
• fever

Respiratory exam findings can vary:

• isolated crackles
• diffuse wheeze
• pleural rubs
• pleural effusion
• pneumothorax
• respiratory distress

Cardiovascular exam

• increased pulmonic component of 2nd heart sound

evidence of DVT may be present:

• leg pain
• swelling
• erythema
• dilated peripheral veins

Clinical Decision Tools

Simplified Wells Clincial Model

low probability: 0-2; moderate 2-6, high >6

PERC rule (PE rule-out criteria)

• age <50
• pulse rate <100 bpm
• oxygen saturation >94%
• no hemoptysis
• no unilateral leg swelling
• no recent major surgery or trauma
• etc
• etc

Lab Investigations

A D-dimer should be done only if low probability.

Arterial blood gases may show acidemia, hypoxemia, and hypercapnia, but even subtle changes such as mild alkalosis may be present.

Elevated LDH can result from tissue infarction, but is neither sensitive nor specific.

D-dimer is sensitive (95-97%) but not specific (45%). It is useful in people with low pre-test probability.

If there is a high probability, not as useful, except to exclude PE.

Degradation product of cross-linked fibrin

Other factors, such as troponin, can help with prognosis, though not diagnosis

Thrombophilia workup

FVL

Protein C and Protein S (though do not measure if on warfarin)

antithrombin III

prothrombin gene mutation

APLA, ACl-A, LAC

Diagnostic Imaging

CT or VQ scan should be done if risk is low but D-dimer is high.

CT/VQ should be first-line if risk is high

ECG

ECG is abnormal in 70%, revealing:

• sinus tachycardia and arrhythmia/flutter
• most specific sign is S₁Q₃T₃ - S in I, Q waves and inverted T in III
• right axis deviation or a right bundle branch block may be present

Chest X-ray

Chest X ray is often normal but can show atelectasis, isolated infiltrates, or small pleural effusion.

Westermark's sign: abrupt cutoff of pulmonary vessels or enlarged central pulmonary arteries.

Hampton's hump: wedge-shaped infarction (usually a later sign).

CT pulmonary angiography (CT PA)

CTPA involves dye that is injected just as the patient enters the CT scanner. It is sensitive for occlusions in the main, lobar, and segmental arteries, but not subsegmental arteries. While it is not as sensitive than VQ scans (described below), it is more specific. CTPA can also be used to evaluate differential diagnoses in situations of chest pain or dyspnea.

If patients have poor kidney function, or are allergic to dye, this test is not an option.

Positive findings include:

• central intra-arterial filling defect
• complete occlusion of pulmonary artery

Ventilation-Perfusion (VQ) Scan

V/Q scan is a nuclear test that compares lung ventilation with lung perfusion using radiolabeled tracer gas. It is more sensitive, but less specific than spiral CT. Nucleotide injection peripherally and assess for areas of low perfusion. Step 2: Radionuclides inhaled, and lung fields assessed.

Tests reveals

• low
• intermediate
• high probability (~80% of PE)

If underlying lung disease, like COPD, makes tests less diagnostic.

Negative predictive value of 91%.

With low probability V/Q and low clinical probability: 4% cahnce of PE

Ultrasound

Doppler compression ultrasound of legs is the most effective bedside test to assess for DVT.