Pulmonary Embolism: Risk, Imaging & Outpatient Pathways

Evaluate pulmonary embolism (PE) with a structured pretest approach, minimize unnecessary CT scans, and treat the right patients at home safely. This guide summarizes practical pathways used in emergency and hospital medicine.

Step 1 — Pretest Probability

• Very low risk: apply PERC (Pulmonary Embolism Rule-out Criteria). If all criteria are negative in a low-clinical-suspicion patient, no D-dimer or imaging is needed.
• Low/Intermediate risk: use Wells or Revised Geneva scores to categorize. Obtain a D-dimer if not high risk.
• High risk (likely PE): skip D-dimer; proceed straight to imaging and start anticoagulation unless contraindicated.

YEARS & Age-Adjusted D-dimer

• Age-adjusted D-dimer (≥50 years): cutoff = age × 10 ng/mL (fibrinogen-equivalent units) when using a 500 ng/mL standard.
• YEARS integrates clinical items (DVT signs, hemoptysis, PE most likely). If none are present, a higher D-dimer threshold can safely exclude PE in many patients.

Step 2 — Imaging Choice

• CTPA (CT pulmonary angiography): first-line for most adults; fast and detects alternatives. Requires iodinated contrast.
• V/Q scan: consider when CXR is normal and avoiding contrast is preferred (pregnancy, severe iodinated-contrast allergy, or advanced CKD). Non-diagnostic results may need further testing.
• Lower-extremity Doppler ultrasound: if positive for proximal DVT in a symptomatic patient, treatment can proceed without chest imaging in many cases.
• Pregnancy: choose V/Q vs CTPA based on local protocols and chest radiograph; LMWH is anticoagulant of choice if PE confirmed.

Step 3 — Risk Stratify Confirmed PE

• Massive (high-risk) PE: sustained hypotension, shock, or arrest → thrombolysis or embolectomy after rapid multidisciplinary discussion.
• Submassive (intermediate-risk): normotensive but RV strain (echo or CT RV/LV ≥1) and/or ↑troponin/BNP. Anticoagulate; consider escalation if decompensating.
• Low-risk: normal vitals, no RV strain, normal biomarkers.
• Disposition tools: sPESI (0 = low risk) and HESTIA criteria help select candidates for outpatient treatment.

Treatment — Anticoagulation

• DOACs are first-line for most non-pregnant adults without severe renal/hepatic disease:
  • Apixaban: 10 mg BID × 7 days, then 5 mg BID; consider 2.5 mg BID for extended phase in select patients.
  • Rivaroxaban: 15 mg BID × 21 days, then 20 mg daily with food; consider 10 mg daily for extended phase in select patients.
• LMWH → warfarin for mechanical valves, significant antiphospholipid syndrome, or when DOACs are unsuitable.
• Pregnancy/lactation: LMWH throughout; avoid warfarin in pregnancy and generally avoid DOACs.
• Cancer-associated: DOACs or LMWH depending on bleeding risk and drug interactions.

Thrombolysis & Interventions

• Systemic thrombolysis for massive PE with shock unless contraindicated.
• Intermediate-risk: not routine; consider rescue lysis or catheter-directed therapy if deterioration despite anticoagulation.
• IVC filter: only if absolute contraindication to anticoagulation or recurrent PE despite therapeutic anticoagulation; retrieve when possible.

Outpatient Pathway (who can go home?)

• sPESI = 0, normal vitals/oxygenation, no RV strain or major comorbidity/bleeding risk, reliable follow-up, and social support.
• HESTIA criteria all negative (no need for IV opioids, no severe renal/liver failure, no social barriers, etc.).
• Provide education, first dose before discharge, 24–72 h follow-up plan, and clear red-flag instructions.

Duration of Therapy

• Provoked by a major transient risk (surgery, temporary immobilization): typically 3 months.
• Unprovoked or persistent risk (thrombophilia, active cancer): consider extended/indefinite therapy if bleeding risk acceptable; use reduced-dose DOAC for secondary prevention when appropriate.

Red Flags (escalate now)

• Hypotension, syncope, rising troponin/BNP, increasing oxygen needs, new RV dysfunction, or significant bleeding on therapy.

Patient FAQs

“Do I need a CT scan every time?” No—low-risk patients may be ruled out with decision tools and D-dimer. Imaging is for patients who can’t be safely excluded.

“How long will I be on blood thinners?” Three months for many provoked events; longer if unprovoked or ongoing risk—your clinician balances recurrence vs bleeding risk.

References & Notes

Practical approach emphasizing pretest probability (PERC/Wells/Geneva/YEARS), judicious imaging, sPESI/HESTIA-guided disposition, anticoagulation first-line with DOACs, and targeted use of thrombolysis and IVC filters. Educational only; follow local protocols.