Diagnosis of Pulmonary Embolism (PE)

1. Symptoms and Signs (Suspect the Diagnosis!)

• Dyspnea (most common), pleuritic chest pain, hemoptysis
• Angina-like chest pain, palpitations
• Wheezing, syncope

• Tachycardia, tachypnea, hypotension (in severe/massive PE)
• Leg swelling and tenderness (suggesting DVT as source)
• Neck vein distension or right ventricular S3 (signs of RV failure)
• Fever, visible anxiety, chest wall tenderness (with pulmonary infarction)
• Reduced oxygen saturation

2. Differential Diagnosis

3. Clinical Probability Scoring

Wells Score (most widely used)

• Score ≤4 = PE unlikely
• Score >4 = PE likely (proceed to imaging)

Revised Geneva Score (no blood gas required)

PERC Rule (to rule out PE without further testing)

• Age <50 years
• Pulse <100/min
• O2 saturation >94%
• No unilateral leg swelling
• No hemoptysis
• No recent surgery/trauma
• No prior DVT/PE
• No oral contraceptive use

YEARS Algorithm (newer)

• No YEARS items + D-dimer <1000 ng/mL → PE excluded
• ≥1 YEARS items + D-dimer <500 ng/mL → PE excluded
• All others → proceed to CT angiography

4. Laboratory Tests

D-Dimer

• A breakdown product of cross-linked fibrin
• Measured by high-sensitivity ELISA or ELISA-derived assay
• Sensitivity and NPV ≥95% when below the cutoff
• Use to exclude PE in low-to-moderate pre-test probability patients
• Not useful in hospitalized patients - many comorbidities elevate it non-specifically
• Age-adjusted cutoff: D-dimer threshold = age × 10 ng/mL (in patients >50 years) increases specificity without sacrificing sensitivity

Troponin & BNP/NT-proBNP

• Used for risk stratification after diagnosis, not to diagnose PE
• Elevated troponin = RV myocardial injury
• Elevated BNP/NT-proBNP = RV strain
• Their combination with RV dysfunction on echo helps stratify intermediate vs. high risk

Arterial Blood Gas (ABG)

• Typically shows hypoxemia, hypocapnia (from hyperventilation), and a raised A-a gradient
• Not diagnostic on its own but supports suspicion
• An O2 saturation of 95% doesn't rule out PE - the patient may be working hard to maintain it

5. Electrocardiogram (ECG)

• Sinus tachycardia - most common finding
• S1Q3T3 pattern - classic but present in only ~20% of cases
• Right bundle branch block (complete or incomplete)
• Right axis deviation
• T-wave inversions in V1-V4 (RV strain pattern)
• ST-segment abnormalities

6. Chest X-Ray (CXR)

• Atelectasis and parenchymal opacity - most common findings (PIOPED data)
• Hampton's hump - wedge-shaped pleural-based opacity (pulmonary infarction)
• Westermark sign - focal oligemia (area of decreased vascularity)
• Palla's sign - enlarged right descending pulmonary artery
• Normal CXR in a hypoxic, dyspneic patient should raise suspicion for PE

7. Imaging

CT Pulmonary Angiography (CTPA) - Gold Standard

• The primary and preferred imaging modality for diagnosing PE
• Direct visualization of clot in pulmonary arteries
• High sensitivity (~83%) and specificity (~96%)
• Also detects alternative diagnoses in ~17-19% of cases
• MDCT-PA (multidetector CT) has replaced conventional pulmonary angiography in most centers
• Contraindications: severe contrast allergy, renal impairment, pregnancy (relative)

Ventilation-Perfusion (V/Q) Scan

• Preferred when CTPA is contraindicated (renal failure, contrast allergy, pregnancy)
• Results reported as: normal, very low, low, intermediate, or high probability
• High-probability scan + high clinical probability → treat for PE
• Normal scan → effectively excludes PE
• PIOPED showed the problem: most patients get an intermediate probability scan, which requires further testing
• Sensitivity/specificity vary depending on underlying lung disease (COPD worsens accuracy significantly)
• Intermediate scans occurred in 60% of COPD patients vs. only 13% in those with normal CXR (PIOPED)

Pulmonary Angiography (Conventional)

• Historical "gold standard" - now rarely used
• Replaced by CTPA
• Still used in select cases (e.g., prior to catheter-directed therapy)

Echocardiography

• Not diagnostic for PE in most cases, but extremely useful for:
  • Detecting RV dilation and dysfunction (RV:LV ratio >0.9)
  • Assessing hemodynamic compromise
  • Risk stratification after diagnosis
  • Bedside evaluation in hemodynamically unstable patients (to identify massive PE quickly)
• Rarely, a clot may be visualized directly in the right heart or main pulmonary artery

MRI/MRA

• Limited utility; lower sensitivity than CTPA
• Used in special circumstances (e.g., pregnancy, contrast allergy)

Compression Ultrasonography (CUS) for DVT

• Useful when PE is suspected but CTPA cannot be done
• Positive CUS (non-compressibility of vein) in a patient with PE symptoms = treat for VTE
• Sensitivity for DVT is lower in pregnancy due to prevalence of isolated pelvic DVT

8. Diagnostic Strategy

Hemodynamically UNSTABLE (shock/hypotension):

1. Immediate bedside echocardiography
2. If RV dilation or clot-in-transit seen → treat for massive (high-risk) PE immediately
3. CTPA if patient can be stabilized

Hemodynamically STABLE:

1. Calculate pre-test probability (Wells / Geneva / PERC)
2. Low probability: D-dimer → if negative, PE excluded; if positive → CTPA
3. Moderate probability: D-dimer → if negative, PE excluded; if positive → CTPA
4. High probability: go straight to CTPA (don't wait for D-dimer result, start anticoagulation)

Key principle: Consider starting anticoagulation before diagnosis is confirmed if pre-test probability is high and bleeding risk is acceptable. (Fuster and Hurst's The Heart, 15th Ed.)

9. Risk Stratification After Diagnosis

• Fuster and Hurst's The Heart, 15th Edition, Chapter 58 (Diagnosis of DVT and PE)
• Fishman's Pulmonary Diseases and Disorders, Chapter 30 (PIOPED study; V/Q scanning)
• 2025 ESVM Guidelines on VTE interventional treatment (PMID: 40587333)

Recent Guidelines on Pulmonary Embolism Management and Treatment Options

Guideline Landscape (2025-2026)

Step 1: Risk Stratification - The Foundation of All Treatment Decisions

Fuster and Hurst's The Heart, 15th Ed. - Fig. 58-6: PE Risk Category Definitions

Step 2: Immediate Supportive Measures

• Oxygen supplementation / mechanical ventilation if needed
• Vasopressors (norepinephrine preferred) for hypotension
• ECMO in refractory cases while planning definitive therapy
• Anticoagulation should be started even before diagnosis is confirmed if suspicion is high and bleeding risk is low - this is the single intervention proven to reduce mortality

Step 3: Anticoagulation - The Cornerstone of Treatment

A. Direct Oral Anticoagulants (DOACs) - Now Preferred First Line

• Rivaroxaban and apixaban allow single-drug therapy - no bridging needed
• DOACs do NOT require INR monitoring and have fewer drug/food interactions than warfarin
• Reversal agents: idarucizumab (dabigatran), andexanet alfa (rivaroxaban, apixaban, edoxaban) - reserved for life-threatening bleeding

B. Parenteral Anticoagulation (Bridge or Primary)

• Unfractionated heparin (UFH): Weight-based IV infusion, titrated to aPTT. Preferred in high-risk PE and when thrombolysis may be needed (reversible, short half-life).
• Low-molecular-weight heparin (LMWH): e.g., enoxaparin 1 mg/kg SC BID. Preferred for cancer-associated PE (see below).
• Fondaparinux: Once-daily SC, anti-Xa, no HIT risk.

C. Vitamin K Antagonists (Warfarin)

• Still used when DOACs are contraindicated
• Target INR 2.0-3.0
• Must overlap with heparin for ≥5 days (warfarin initially prothrombotic due to protein C/S depletion)
• Initial dose 10 mg for 2 days; 5 mg for elderly/malnourished

Step 4: Advanced/Escalated Therapy

High-Risk (Massive) PE with Hemodynamic Collapse

Systemic Thrombolysis

• Alteplase 100 mg IV over 2 hours is the primary reperfusion therapy for high-risk PE with hemodynamic instability
• Rapidly dissolves thrombus and restores hemodynamics
• Major risk: bleeding, including intracranial hemorrhage (~2%)
• Absolute contraindications: recent stroke, active internal bleeding, recent CNS surgery
• Reduced-dose thrombolysis is being studied (37060258) but not yet standard

Surgical Embolectomy

• Indicated when thrombolysis is contraindicated or fails
• High-volume centers report good outcomes
• Direct surgical extraction from pulmonary arteries under cardiopulmonary bypass

Intermediate-Risk (Submassive) PE

Catheter-Directed Thrombolysis (CDT)

• Low-dose tPA infused directly into the clot via catheter
• Lower bleeding risk than systemic thrombolysis
• Standard approach for intermediate PE where intervention is warranted

Large-Bore Mechanical Thrombectomy (LBMT)

• The PEERLESS RCT (2025, Circulation, n=550, PMID: 39470698) compared LBMT vs CDT in intermediate-risk PE with RV dilation:
  • LBMT won on the primary hierarchical composite (win ratio 5.01, p<0.001)
  • Fewer episodes of clinical deterioration (1.8% vs 5.4%)
  • Markedly less post-procedural ICU use (41.6% vs 98.6% ICU admission)
  • Shorter hospital stay (4.5 vs 5.3 nights)
  • No difference in mortality, intracranial hemorrhage, or major bleeding
  • Better dyspnea scores and RV function at 24 hours
  A 2025 meta-analysis (PMID: 40602356) pooling PEERLESS + 6 observational studies confirmed MT results in shorter hospital stays vs CDT, with comparable mortality and readmission rates overall.

Bottom line on catheter therapies: LBMT appears to offer clinical advantages over CDT for intermediate-risk PE, particularly in reducing ICU utilization. However, mortality is equivalent and further RCTs are needed before definitive guideline adoption.

IVC Filter Placement

• Not routinely recommended
• Indications: PE with absolute contraindication to anticoagulation, or recurrent PE despite adequate anticoagulation
• Retrievable filters preferred

Step 5: Treatment by Special Populations

Cancer-Associated PE (CAT)

• DOACs reduced recurrent VTE significantly vs LMWH (IRR 0.66, 95% CI 0.56-0.79)
• Total bleeding and all-cause mortality were not significantly different
• DOACs are now considered a viable and potentially preferred option over LMWH in many cancer patients (preferred DOACs: apixaban, rivaroxaban, edoxaban)
• Exception: luminal GI or genitourinary cancers carry higher bleeding risk with DOACs - LMWH still preferred there

Low-Risk PE - Outpatient Management

• HESTIA criteria or sPESI = 0 identifies patients safe for home treatment
• DOAC started in ED, patient discharged with close follow-up
• Reduces hospitalization without increasing adverse events

Pregnancy

• LMWH is the drug of choice (DOACs are teratogenic; warfarin teratogenic in weeks 6-12)
• Dose adjustments needed as pregnancy progresses
• Postpartum: DOACs can be used after delivery

Duration of Anticoagulation

PE Response Teams (PERT)

Long-Term Follow-Up

• Repeat imaging if symptoms persist (to detect CTEPH - chronic thromboembolic pulmonary hypertension, which develops in ~1% of cases)
• Thrombophilia testing (especially for unprovoked or recurrent PE)
• Duration of anticoagulation reassessment

• 2026 AHA/ACC PE Guideline (Circulation, PMID 41712677) - the most current comprehensive guidance
• PEERLESS RCT 2025 - LBMT vs CDT in intermediate-risk PE (Circulation, PMID 39470698)
• DOACs vs LMWH in cancer-associated PE - meta-analysis 2025 (Am J Cardiol, PMID 40578592)
• MT vs CDT meta-analysis 2025 (Am J Emerg Med, PMID 40602356)
• Fuster and Hurst's The Heart, 15th Edition, Chapter 58