What is the recommended diagnostic and therapeutic approach for a patient with suspected pulmonary embolism?

Diagnostic and Therapeutic Approach for Suspected Pulmonary Embolism

For patients with suspected pulmonary embolism, immediately assess clinical probability using risk factors and symptoms, obtain basic investigations (chest X-ray, ECG, arterial blood gases), and initiate anticoagulation while pursuing definitive imaging—with the diagnostic pathway determined by hemodynamic stability and clinical probability. 1, 2

Initial Clinical Assessment

Step 1: Recognize High-Risk Clinical Patterns

Suspect PE when patients present with any of these cardinal patterns 3, 1:

• Sudden collapse with raised jugular venous pressure (faintness and/or hypotension) indicating massive PE 3, 1
• Pulmonary hemorrhage syndrome (pleuritic pain and/or hemoptysis) 3, 1
• Isolated dyspnea (breathlessness without cough, sputum, or chest pain) 3, 1

Step 2: Document Critical Vital Signs

Record respiratory rate in all patients—tachypnea >20/min is present in most PE patients and is a key diagnostic finding 3, 1, 2. The combination of tachypnea, pleuritic pain, and arterial hypoxemia strongly suggests PE 3, 1.

Common pitfall: PE is easily missed in elderly patients, those with severe cardiorespiratory disease, and when isolated dyspnea is the only symptom 3.

Step 3: Assess Clinical Probability Score

Use this structured scoring system 3:

Score +1 if other diagnoses are unlikely (on clinical grounds and after basic investigations) 3

Score +1 if major risk factors present 3:

• Recent immobilization or major surgery 3, 1
• Recent lower limb trauma and/or surgery 3, 1
• Clinical deep vein thrombosis 3
• Previous proven DVT or PE 3, 1
• Pregnancy or postpartum 3, 1
• Major medical illness 3

Important caveat: PE is rare if age <40 with no risk factors; oral contraceptives are only a minor risk factor 3. Young women on oral contraception with isolated pleuritic chest pain, respiratory rate <20/min, and normal chest radiograph are very unlikely to have PE 1.

Mandatory Basic Investigations

Perform these tests in all patients with suspected PE 3:

• Chest radiography (abnormal in >80% of PE cases) 3, 4
• ECG (may show tachycardia, T wave inversion in V1-V2, PR displacement) 3, 4
• Arterial blood gas measurements (typically shows hypoxia and hypocapnia) 3, 2, 4

Critical exclusion rule: In the absence of all three findings—tachypnea (>20/min), pleuritic pain, and arterial hypoxemia—PE can be excluded 3.

Diagnostic Pathway Based on Clinical Probability

Low or Intermediate Clinical Probability

Use D-dimer testing as the initial diagnostic step 2, 5, 6:

• If D-dimer is normal (<500 ng/mL): PE is excluded; withhold anticoagulation and further testing 5, 6
• The combination of low clinical probability and normal D-dimer has a 3-month thromboembolic risk of 0% 5, 6
• If D-dimer is elevated: Proceed to imaging 5, 6

Important limitation: D-dimer is unreliable in postoperative patients (always elevated regardless of PE) 1.

High Clinical Probability

Proceed directly to CT pulmonary angiography (CTPA) without D-dimer testing 2. D-dimer tests are useless in high-probability settings 7.

Imaging Strategy

Lung scanning should be performed within 24 hours of clinical suspicion 3. Request forms should include clinical probability estimate, and scans should be reported with probability assessment (high, intermediate, or low) 3.

For patients with indeterminate lung scans: Further imaging is required rather than management based on clinical features alone 3.

Consider leg vein imaging (compression ultrasonography) as first-line investigation in patients with 3, 8:

• Previous PE
• Clinical DVT
• Chronic cardiorespiratory disease

The combination of negative spiral CT and negative ultrasonography safely excludes PE in low/intermediate probability patients (1.8% 3-month VTE risk) 8.

Pulmonary angiography should be considered when other investigations fail to confirm diagnosis 3. Hospitals must have clearly defined systems for arranging emergency pulmonary angiography 3.

Immediate Therapeutic Management

Anticoagulation Initiation

Start therapeutic anticoagulation immediately when PE is suspected (unless bleeding contraindications exist), even while diagnostic workup is ongoing 2, 7.

Intravenous heparin dosing 3:

• Weight-adjusted (preferred): 80 IU/kg bolus, then 18 IU/kg/hour maintenance 3
• Standard: 5000-10,000 IU bolus, then 1300 IU/hour maintenance 3
• Adjust infusion to maintain APTT 1.5-2.5 times control (45-75 seconds) 3

APTT monitoring schedule 3:

• After initial bolus: 4-6 hours later
• After any dose change: 6-10 hours later
• Once therapeutic: Daily

Warfarin initiation 3:

• Start 5-10 mg daily for 2 days, then adjust to INR 2.0-3.0 3
• Discontinue heparin after 5 days of warfarin AND INR ≥2.0 3

Modern alternative: Direct oral anticoagulants are preferred over warfarin for ease of use in outpatient settings 9.

High-Risk (Massive) PE Management

Massive PE is defined by systemic hypotension or cardiogenic shock 7.

Perform immediate bedside transthoracic echocardiography to differentiate PE from other acute conditions and assess right ventricular dysfunction 1, 7. When clinical probability is high, right ventricular dilatation on echo confirms diagnosis without additional testing 7.

Thrombolytic therapy is indicated for hemodynamically unstable patients 3, 1:

Dosing regimens 3:

• rtPA: 100 mg over 2 hours (for stable patients) OR 50 mg IV bolus (for cardiac arrest/rapidly deteriorating patients) 3, 1
• Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours (plus hydrocortisone to prevent circulatory instability) 3
• Urokinase: 4400 IU/kg over 10 minutes, then 4400 IU/kg/hour for 12 hours 3

Before thrombolysis: Stop heparin; after treatment, resume maintenance heparin dose 3.

Thrombolytic therapy can be given via peripheral vein or pulmonary artery catheter 3.

Intermediate-Risk PE Management

For intermediate-risk patients (hemodynamically stable with RV dysfunction): Anticoagulation is the primary treatment rather than immediate thrombolysis 1. Close monitoring with contingency planning for reperfusion is recommended if deterioration occurs 1.

Controversial area: Current data do not confirm that thrombolytic therapy decreases mortality in submassive PE, though a clinically significant benefit cannot be excluded 7.

Risk-Stratified Disposition

Low-Risk PE: Outpatient Management Criteria

Outpatient treatment is safe for appropriately selected patients with 30-day mortality 1.7%, recurrent VTE 1.8%, and major bleeding 0.97% 9.

Hestia criteria for safe discharge (all must be absent) 9:

• Hemodynamic instability (systolic BP <100 mmHg) 9
• Need for thrombolysis or embolectomy 9
• Oxygen requirement >24 hours 9
• Active bleeding or high bleeding risk 9
• Severe pain requiring IV analgesia 9

Discharge requirements 9:

• Clear return precautions for worsening dyspnea, chest pain, syncope, or hemodynamic instability
• Follow-up within 24-72 hours to assess clinical response and anticoagulation adherence
• Minimum 3 months of anticoagulation for first unprovoked PE 9

Discharge Checklist for All Patients 3:

• INR between 2.0-3.0 (if on warfarin)
• General practitioner informed of diagnosis and treatment duration
• Patient aware of anticoagulant side effects and drug interactions
• Written information on warfarin therapy provided
• Anticoagulant supervision appointment arranged
• Follow-up review at 6-12 weeks scheduled

Duration of Anticoagulation

At 6-12 week follow-up 3:

• First episode with temporary risk factors: Consider discontinuing anticoagulation 3
• Idiopathic or recurrent episode: Consider evaluation for thrombophilic disorder and occult malignancy 3

Occult malignancy screening is only necessary in patients presenting with PE without apparent risk factors or with recurrent PE 3.

Special Considerations

Subsegmental PE: Clinical significance remains controversial; may represent false-positive findings requiring radiologist discussion before committing to anticoagulation 1. Evidence suggests patients with suspected or proven minor embolism without residual DVT may not necessarily require treatment, particularly if risk factors are temporary 3.

Female patients on oral contraception: Seek specialist advice regarding contraception management 3.