What is the appropriate treatment for a suspected pulmonary embolism in an adult patient with risk factors such as recent immobility, cancer, or history of deep vein thrombosis, presenting with symptoms like sudden onset dyspnea, chest pain, and possibly syncope?

Treatment of Suspected Pulmonary Embolism

Start intravenous heparin immediately based on high or intermediate clinical suspicion of pulmonary embolism, before diagnostic confirmation is obtained, unless active bleeding or absolute contraindications exist. 1, 2, 3

Immediate Anticoagulation Strategy

Empiric anticoagulation takes priority over diagnostic confirmation when clinical suspicion is moderate to high. The British Thoracic Society explicitly recommends starting heparin before PE diagnosis is clarified to prevent mortality from delayed treatment. 1, 2

Heparin Dosing Protocol

Unfractionated heparin (UFH) is the preferred initial agent:

• Initial bolus: 5,000-10,000 units IV (or 80 IU/kg for weight-adjusted dosing) 1, 4
• Continuous infusion: 1,300 IU/hour (or 18 IU/kg/hour weight-adjusted) in 1,000 mL of 0.9% sodium chloride 1, 4
• Target aPTT: 1.5-2.5 times control (45-75 seconds) 1, 5, 4
• Monitoring schedule: Check aPTT 4-6 hours after initial bolus, then 6-10 hours after any dose adjustment, then daily once therapeutic 1

Alternative subcutaneous dosing (if IV access problematic): 10,000-20,000 units subcutaneously every 8-12 hours after initial 5,000 unit IV bolus 1, 4

Risk Stratification and Clinical Assessment

Assess hemodynamic stability first—this determines whether thrombolysis is needed:

• High-risk (massive) PE: Hypotension (systolic BP <90 mmHg), shock, or cardiac arrest 1, 5, 3
• Intermediate-risk: Hemodynamically stable but with right ventricular dysfunction 5, 3
• Low-risk: Hemodynamically stable without RV dysfunction 3

Key clinical features to document: 1, 6

• Sudden onset dyspnea (present in 78-81% of cases) 6
• Pleuritic chest pain (39-56% of cases) 6
• Syncope or presyncope (22-26% of cases) 6
• Hemoptysis (5-7% of cases) 6
• Tachypnea >20 breaths/min 1

Risk factors present in 80-90% of PE patients: 1

• Immobilization >1 week 1
• Recent surgery (especially orthopedic or abdominal) 1
• Active cancer 1
• Previous DVT/PE 1
• Lower limb fractures or surgery 1

Diagnostic Workup (While Anticoagulation Continues)

Initial Testing

Perform these tests in all suspected PE patients: 1

• Chest radiograph 1
• ECG (look for right ventricular strain: T-wave inversion V1-V4, S1Q3T3 pattern, right bundle branch block) 1
• Arterial blood gas (assess for hypoxemia and hypocapnia) 1
• Respiratory rate documentation 1

D-dimer testing caveats: 1, 2

• Normal D-dimer excludes PE only in low clinical probability patients 1
• Do NOT use D-dimer in postoperative patients—it will be elevated regardless of PE presence 2, 3
• Do NOT use D-dimer in cancer patients—frequently elevated at baseline 7

Imaging Strategy

First-line imaging depends on clinical context:

CT Pulmonary Angiography (CTPA):

• Preferred first-line test in most patients 3, 7, 8
• Negative high-quality CTPA reliably excludes PE 3, 8
• Pitfall: Can miss subsegmental emboli (sensitivity 83-100%) 2
• Pitfall: May detect clinically insignificant subsegmental PE 8

Ventilation-Perfusion (V/Q) Scan:

• Preferred in younger patients, pregnancy, and renal insufficiency (lower radiation exposure) 2, 8
• Should be performed within 24 hours of clinical suspicion 1
• Normal V/Q scan excludes PE 2, 8
• High probability V/Q scan confirms PE 8
• Indeterminate scans require further imaging, not clinical judgment alone 1

Lower extremity venous ultrasound:

• Perform as first-line test in patients with: 1, 2
  • Previous PE 1
  • Clinical signs of DVT 1
  • Chronic cardiorespiratory disease 1
• Positive DVT confirms need for anticoagulation even without confirmed PE 2, 3

Pulmonary angiography:

• Reserved for cases where other investigations fail to confirm diagnosis 1

Thrombolytic Therapy for High-Risk PE

Thrombolysis is indicated for hemodynamically unstable patients with systemic hypotension or shock. 1, 5, 7

Dosing regimens: 1

• rtPA: 100 mg over 2 hours 1
• Streptokinase: 250,000 units over 20 minutes, then 100,000 units/hour for 24 hours (plus hydrocortisone to prevent circulatory instability) 1
• Urokinase: 4,400 IU/kg over 10 minutes, then 4,400 IU/kg/hour for 12 hours 1

Stop heparin during thrombolytic infusion, then resume maintenance dosing afterward. 1

Most contraindications to thrombolysis in massive PE are relative, not absolute—weigh mortality risk of untreated massive PE against bleeding risk. 5

Surgical embolectomy is indicated if absolute contraindications to thrombolysis exist or thrombolysis fails. 5

Transition to Oral Anticoagulation

Warfarin initiation: 1, 9

• Start warfarin 5-10 mg daily for 2 days, then adjust to maintain INR 2.0-3.0 1, 9
• Continue heparin for minimum 5 days AND until INR ≥2.0 for two consecutive days 1, 5, 9
• Check INR every 1-2 days initially 1

Duration of anticoagulation: 9, 7

• Provoked PE (transient risk factor): 3 months 9, 7
• First unprovoked PE: 6-12 months minimum 9, 7
• Recurrent PE or persistent risk factors: Indefinite therapy 9, 7
• Cancer-associated PE: Extended therapy while cancer active 7

Direct oral anticoagulants (DOACs) are preferred over warfarin for most patients due to lower bleeding risk, no routine monitoring required, and fewer drug interactions. 7, 8 However, dabigatran and edoxaban require initial parenteral anticoagulation before starting. 8

Critical Pitfalls to Avoid

• Never delay anticoagulation waiting for imaging—mortality risk of untreated PE exceeds bleeding risk in suspected cases 2, 3
• Do not rely on absence of tachypnea, pleuritic pain, AND hypoxemia to exclude PE—PE can be excluded only if all three are absent 1
• Do not dismiss subsegmental PE on CTPA without clinical correlation—discuss findings with radiology 3
• Do not use D-dimer in postoperative or cancer patients 2, 3
• Recognize that PE is both overdiagnosed and underdiagnosed in clinical practice—maintain appropriate clinical suspicion 1

Special Considerations

Pleuritic chest pain management: Once PE is being appropriately treated, administer NSAIDs for 1-2 weeks as first-line treatment. 5

Occult malignancy screening: Only consider in patients presenting with PE without apparent risk factors or with recurrent PE. 1