How should I evaluate and manage a patient presenting with acute dyspnea, pleuritic chest pain, tachypnea, tachycardia, hypoxia, or unexplained syncope and risk factors such as recent surgery, immobilization, active cancer, prior venous thromboembolism, pregnancy, hormonal therapy, obesity, or known thrombophilia?

Evaluation and Management of Suspected Pulmonary Embolism

Start therapeutic anticoagulation immediately in patients with intermediate or high clinical probability of PE before obtaining diagnostic imaging, as early treatment reduces mortality. 1

Initial Clinical Assessment

Measure Vital Signs and Document Key Findings

• Record respiratory rate in every patient—tachypnea >20 breaths/min is present in most PE cases and significantly raises clinical probability. 2, 1
• Measure heart rate—tachycardia ≥95 beats/min increases the likelihood of PE. 1
• Check oxygen saturation, but recognize that up to 40% of PE patients have normal SaO₂, so normal oxygen levels never exclude PE. 1
• Assess hemodynamic stability first—systolic blood pressure <90 mmHg or a drop ≥40 mmHg lasting >15 minutes identifies high-risk PE requiring emergent management and possible thrombolysis. 1, 3

Recognize Classic Presentations

PE presents in three main patterns: 2

1. Sudden collapse with elevated jugular venous pressure (syncope/hypotension)—associated with higher prevalence of right ventricular dysfunction 1
2. Pulmonary hemorrhage syndrome (pleuritic pain and/or hemoptysis) 2
3. Isolated dyspnea (breathlessness without cough, sputum, or chest pain)—this atypical presentation is frequently missed 2

The triad of tachypnea >20/min, pleuritic pain, and arterial hypoxemia strongly suggests PE; the absence of all three virtually excludes the diagnosis. 2, 4

Identify Risk Factors

Risk factors are present in 80–90% of PE patients: 2, 1, 4

Strong risk factors (odds ratio >10): 2

• Immobilization >1 week
• Recent surgery (especially within 3 months requiring endotracheal intubation) 2, 5
• Lower limb fracture or orthopedic surgery (hip/knee replacement) 2
• Prior venous thromboembolism 2, 5
• Active cancer (especially metastatic disease) 2
• Spinal cord injury 2

Moderate risk factors (odds ratio 2–9): 2

• Pregnancy and post-partum period 2
• Hormonal therapy (oral contraceptives, hormone replacement therapy—new use increases risk) 2, 5
• Known thrombophilia 2
• Congestive heart failure or respiratory failure 2
• Central venous catheters 2

Important caveat: Treated/inactive cancer, smoking, and obesity have not been found to increase PE probability in symptomatic emergency department patients. 5

Stratify Clinical Probability

Use a validated scoring system (Wells or revised Geneva score) before ordering any laboratory tests. 1

Wells Score or Revised Geneva Score

The revised Geneva score incorporates: 1

• Previous PE/DVT
• Heart rate
• Recent surgery or fracture
• Hemoptysis
• Active cancer
• Unilateral leg pain

Classify patients into low, intermediate, or high clinical probability categories before proceeding. 1

Obtain Initial Diagnostic Tests

Order chest radiography, ECG, and arterial blood gas analysis in all patients with suspected PE. 2, 1

• Chest X-ray is abnormal in >80% of PE cases (though findings are non-specific) and helps exclude alternative diagnoses such as pneumothorax or pneumonia. 1, 6
• ECG may reveal right ventricular strain patterns (T-wave inversion V1–V4, S1Q3T3, right bundle branch block) in more severe PE. 1
• Arterial blood gases frequently show hypoxia and hypocapnia, but normal values do not exclude PE. 2, 6

Diagnostic Algorithm Based on Clinical Probability

Low Clinical Probability (<15%)

1. Apply the Pulmonary Embolism Rule-Out Criteria (PERC) first—if all eight criteria are met (age <50 years, heart rate <100/min, oxygen saturation >94%, no recent surgery or trauma, no prior VTE, no hemoptysis, no unilateral leg swelling, no estrogen use), PE workup can be stopped. 1, 3

2. If any PERC criterion is positive, obtain a highly sensitive D-dimer assay (e.g., Vidas ELISA). 1

3. A D-dimer <500 ng/mL (or age-adjusted: age × 10 ng/mL for patients >50 years) safely excludes PE with a 3-month thromboembolic risk <1%. 1, 3

4. When D-dimer is elevated, proceed directly to CT pulmonary angiography (CTPA). 1

Intermediate Clinical Probability

1. Obtain a D-dimer test (PERC is not used in this group). 1

2. A D-dimer <500 ng/mL (or age-adjusted) excludes PE without imaging. 1

3. If D-dimer is elevated, advance to CTPA. 1

4. Start therapeutic anticoagulation immediately while awaiting imaging results. 2, 1, 4

High Clinical Probability (>40%)

1. Proceed directly to CTPA; D-dimer testing is not recommended because a negative result does not reliably exclude PE. 1, 3

2. Initiate therapeutic anticoagulation before imaging confirmation. 2, 1, 4

Imaging Strategies

CT Pulmonary Angiography (First-Line)

• CTPA is the first-line imaging modality for hemodynamically stable patients. 1, 4, 7
• A normal high-quality CTPA in patients with low or intermediate clinical probability definitively rules out PE—no further testing is needed. 1
• CTPA demonstrating a segmental or more proximal filling defect confirms PE. 1, 4
• Imaging should be performed within 24 hours of clinical suspicion for non-massive PE; within 1 hour for suspected massive PE. 2, 1

Ventilation-Perfusion (V/Q) Scanning

Use V/Q scanning when CTPA is contraindicated (renal failure, contrast allergy, pregnancy) or unavailable. 1, 7

V/Q scanning should only be performed when: 1

• On-site V/Q facilities are available
• Chest radiograph is normal
• The patient has no significant concurrent cardiopulmonary disease
• Standardized reporting criteria are applied
• Any non-diagnostic result will be followed by further imaging

V/Q scan interpretation: 2, 1

• Normal perfusion scan → PE excluded 1
• High-probability scan + high clinical probability → PE confirmed 1
• All other combinations require CTPA or pulmonary angiography 1

Lower-Extremity Compression Ultrasound

• Perform ultrasound before CT imaging in patients with clinical signs of DVT, renal failure, contrast allergy, or pregnancy. 1
• Detection of proximal DVT on ultrasound confirms venous thromboembolism—start anticoagulation without further pulmonary imaging. 1
• A normal lower-extremity ultrasound does not exclude PE (only 30–50% of PE patients have detectable DVT)—proceed to lung imaging if D-dimer is elevated. 1
• Leg vein imaging should be performed as a first-line investigation in patients with previous PE, clinical DVT, or chronic cardiorespiratory disease. 2

Management of Massive PE (Hemodynamically Unstable)

Massive PE is highly likely when the patient presents with collapse, hypotension, unexplained hypoxia, engorged neck veins, or a right ventricular gallop. 1

1. Perform bedside transthoracic echocardiography immediately to assess right ventricular dysfunction and differentiate PE from other causes of shock. 1, 8

2. Both CTPA and echocardiography can reliably diagnose clinically massive PE. 1

3. In hemodynamically unstable patients, thrombolytic therapy may be initiated based solely on compatible echocardiographic findings. 2, 1

4. Once the patient stabilizes, obtain definitive diagnosis with CTPA. 1

5. A normal lung scan or CTPA in the setting of massive PE should prompt investigation for alternative causes of shock. 1

Anticoagulation Management

Immediate Anticoagulation

Heparin should be started on the basis of high or intermediate clinical suspicion before the diagnosis of PE is clarified. 2, 4

Unfractionated heparin (UFH): 2

• Initial bolus: 80 units/kg IV
• Maintenance infusion: 18 units/kg/hour
• Preferred in massive PE or when rapid reversal may be required 1
• Adjust infusion rate until APTT = 1.5–2.5 × control (45–75 seconds) 2

Low-molecular-weight heparin (LMWH): 1

• Preferred over UFH for non-massive PE because it offers equivalent efficacy and safety with greater ease of use 1

Thrombolytic Therapy

Thrombolytic therapy is indicated in patients who are hemodynamically unstable, particularly if systemic hypotension is present. 2, 8

Systemic thrombolysis is associated with a 1.6% absolute reduction in mortality (from 3.9% to 2.3%). 3

Regimens: 2

• rtPA: 100 mg over 2 hours
• Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours (plus hydrocortisone to prevent circulatory instability)
• Urokinase: 4400 IU/kg over 10 minutes, then 4400 IU/kg/hour for 12 hours

Consider surgical embolectomy or catheter-directed treatment if thrombolysis is contraindicated or fails. 8

Long-Term Anticoagulation

Heparin should be continued until maintenance anticoagulation with warfarin is achieved. 2

Direct oral anticoagulants (DOACs)—apixaban, edoxaban, rivaroxaban, or dabigatran—are first-line therapy for hemodynamically stable PE and are noninferior to heparin/warfarin with a 0.6% lower rate of bleeding. 9, 3

Warfarin: 2

• Initial dose: 5–10 mg daily for 2 days
• Adjust dose to INR 2.0–3.0
• Discontinue heparin 5 days after starting warfarin if INR ≥2.0 2

Common Pitfalls to Avoid

• Never use D-dimer as a routine screening test—order it only after clinical probability assessment. 1, 4
• Avoid D-dimer testing in high-probability patients or hospitalized patients with comorbidities (infection, cancer, inflammation, recent surgery) due to low diagnostic yield. 1
• Do not order a V/Q scan when the chest X-ray is abnormal or the patient has chronic cardiopulmonary disease, as results are likely non-diagnostic. 1
• Never delay anticoagulation for imaging—start treatment based on clinical suspicion alone. 8
• Do not rely on normal oxygen saturation to rule out PE, as normal SaO₂ occurs in approximately 40% of cases. 1
• Never use D-dimer to exclude PE in the postoperative setting. 8

Special Populations

Pregnancy and Post-Partum

• Both V/Q scanning and CTPA are considered safe during pregnancy, but V/Q is often preferred to reduce fetal radiation exposure. 1
• When feasible, start with lower-extremity ultrasound to avoid any radiation if DVT can be confirmed. 1
• NOACs are contraindicated; use LMWH or UFH for anticoagulation. 1, 8
• Wait at least 4 hours after epidural catheter removal before administering therapeutic LMWH. 8
• Continue anticoagulation for minimum 6 weeks postpartum AND minimum 3 months total duration from the acute PE event. 8
• LMWH and warfarin are safe during breastfeeding. 8