Pulmonary Embolism: Wells/Geneva, PERC, D-dimer & CT-PA — Who to Scan and Who to Treat

Don’t shotgun CT everyone with chest pain. Start with pretest probability, apply PERC in the truly low-risk, use an age-adjusted D-dimer for the rest, and reserve CT-PA for those who actually need it. Then treat based on risk: massive, intermediate, or low.

Step 1 — Establish pretest probability

• Wells (common cut-offs): Low ≤4 (PE unlikely), High >4 (PE likely). Components include DVT signs, PE more likely than alternatives, tachycardia, immobilization/surgery, prior VTE, hemoptysis, cancer.
• Revised Geneva is all objective (age, tachycardia, surgery, prior VTE, hemoptysis, unilateral leg pain, pain on DVT palpation).
• Clinical gestalt is valid—document it and be consistent with the pathway below.

Step 2 — If very low risk, use PERC to avoid any testing

If clinician gestalt is low and all PERC items are negative, no D-dimer or imaging.

• Age <50
• HR <100
• SpO₂ ≥95% (room air)
• No hemoptysis
• No estrogen use
• No prior VTE
• No recent surgery/trauma (≤4 weeks requiring hospitalization)
• No unilateral leg swelling

Step 3 — D-dimer strategy (for low/intermediate risk who fail PERC)

• Age-adjusted cutoff (FEU units): for age >50, threshold = age × 10 ng/mL (e.g., 72→720 ng/mL). For ≤50, use 500 ng/mL.
• If D-dimer below cutoff → PE ruled out (no imaging).
• If D-dimer above cutoff → proceed to imaging.
• High pretest probability (Wells >4): skip D-dimer; go straight to imaging.

Step 4 — Imaging choices

• CT-pulmonary angiography (CT-PA) is first-line in most adults.
• V/Q scan preferred when CT contraindicated (contrast allergy, pregnancy with normal CXR, severe renal failure) or when radiation strategy favors V/Q.
• Lower-extremity venous ultrasound can confirm DVT and allow treatment without chest imaging in selected cases (pregnancy, renal failure).
• Unstable patient: bedside echo for RV strain can support empiric lytics while arranging definitive imaging if feasible.

Step 5 — Risk stratify confirmed PE (guides therapy & disposition)

• Massive (high-risk): hypotension/shock (SBP <90 or vasopressors), syncope, cardiac arrest.
• Intermediate-risk (submassive): normotensive with RV dysfunction (echo/CT) and/or cardiac biomarker elevation (troponin/BNP).
• Low-risk: none of the above; consider sPESI = 0 or satisfying Hestia criteria for outpatient treatment.

Step 6 — Treatment pathways

Anticoagulation (default for all unless contraindicated)

• DOAC first-line for most: apixaban (10 mg BID ×7 days → 5 mg BID) or rivaroxaban (15 mg BID ×21 days → 20 mg daily).
• LMWH favored in pregnancy and many cancer patients (or consider DOACs with caution in GI/GU malignancy).
• Heparin infusion for massive PE, CDT/systemic thrombolysis candidates, extremes of weight, or high bleeding concern.
• Renal/hepatic adjustments as per drug labeling; avoid DOACs in pregnancy and severe renal failure without specialist input.

High-risk (massive) PE

• Resuscitate: oxygen, cautious fluids, norepinephrine for hypotension, consider inhaled pulmonary vasodilators as bridge in refractory hypoxemia/RV failure.
• Systemic thrombolysis if no absolute contraindications (e.g., alteplase 100 mg over 2 h) — institutional protocols vary.
• If lytics contraindicated or fail: catheter-directed thrombolysis or mechanical thrombectomy with PERT team; surgical embolectomy where available.

Intermediate-risk (submassive) PE

• Anticoagulate and closely monitor. No routine systemic lytics; consider CDT for clinical deterioration or severe RV dysfunction after multidisciplinary discussion.

Low-risk PE (outpatient candidates)

• sPESI = 0 or meeting Hestia criteria, reliable follow-up, stable home supports → home DOAC with early clinic/telehealth check.
• Provide explicit return precautions and adherence counseling.

Duration of anticoagulation

• Provoked (transient risk: surgery, trauma, immobilization, estrogen): typically 3 months.
• Unprovoked or persistent risks: consider extended/indefinite therapy if bleeding risk acceptable (often reduced-dose DOAC long-term).
• Cancer-associated: continue while cancer active or therapy ongoing; reassess regularly.
• Pregnancy/post-partum: LMWH during pregnancy; treat for ≥3 months and at least 6 weeks post-partum.

IVC filters — rare, temporary

• Place only if acute VTE with an absolute contraindication to anticoagulation or recurrent PE despite verified therapeutic anticoagulation.
• Plan for retrieval once anticoagulation is possible.

Follow-up & complications

• Early visit/telehealth (within 1–2 weeks) for adherence, bleeding checks, and symptom trajectory.
• CTEPH suspicion: persistent dyspnea/exercise intolerance at ~3 months → V/Q scan and referral.

Special populations

• Pregnancy: prefer V/Q if CXR normal; LMWH for treatment; involve obstetrics.
• Renal failure (CrCl <30): avoid contrast when possible; use heparin/warfarin or adjusted LMWH with monitoring.
• Active cancer: LMWH or DOAC based on bleeding site risk and interactions.

Pearls & pitfalls

• Low risk + PERC negative means no testing. Over-testing yields false positives and harms.
• Don’t use D-dimer in high pretest probability—go straight to imaging.
• Massive PE needs pressors + reperfusion pathway now, not tomorrow.

Patient FAQs

“Why no scan if my blood test is low?” A negative D-dimer in low/intermediate risk effectively rules out a clot—scans add radiation/contrast risk without benefit.

“How long will I take blood thinners?” Many need 3 months; if your clot was unprovoked or risks persist, we may continue longer at a safer, lower dose.

References & Notes

Practical PE pathway: structured pretest probability → PERC → age-adjusted D-dimer → CT-PA/VQ when indicated, then risk-based therapy (massive/intermediate/low), with selective lysis/CDT and outpatient care when safe. Follow local protocols. Educational only.