Obstruction of pulmonary arterial circulation, usually by deep venous thrombus.
Also known as: PE, pulmonary embolism, VTE, venous thromboembolism, saddle embolus, massive PE, submassive PE
Overview
Acute occlusion of one or more pulmonary arteries by thromboembolus, most commonly originating from a lower-extremity deep vein thrombosis. Severity ranges from incidental subsegmental PE to massive PE with hemodynamic collapse.
Epidemiology
VTE affects ~1-2 per 1000 adults annually. PE causes ~100,000 US deaths/year. Recurrence rate ~30% over 10 years without secondary prevention.
Try two board-style Pulmonary Embolism questions
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Question 1PulmonaryEasy
A 32-year-old woman has a confirmed pulmonary embolism on CT pulmonary angiography. She is hemodynamically stable with HR 95 and BP 118/76. Which of the following is the most appropriate initial treatment?
AOral rivaroxaban as single-agent therapy
BSystemic alteplase thrombolysis
CLMWH bridged to oral warfarin
DIV unfractionated heparin then warfarin
Reveal answer & full explanation
Correct answer: A — Oral rivaroxaban as single-agent therapy
AOral rivaroxaban as single-agent therapy✓
BSystemic alteplase thrombolysis
CLMWH bridged to oral warfarin
DIV unfractionated heparin then warfarin
Why Oral rivaroxaban as single-agent therapy is correct
For low-to-intermediate risk pulmonary embolism (PE) in a hemodynamically stable patient, direct oral anticoagulants (DOACs) are first-line
Rivaroxaban uses a dual-dose regimen: 15 mg twice daily for 21 days, then 20 mg once daily
This regimen avoids the need for parenteral bridging
Treatment duration is at least 3 months
Why the others are wrong
Systemic alteplase thrombolysis — systemic thrombolytics are reserved for massive PE with hemodynamic instability; this patient is hemodynamically stable
LMWH bridged to oral warfarin — effective, but warfarin requires at least 5 days of parenteral overlap plus INR monitoring to a target of 2–3, which a single-agent DOAC avoids
IV unfractionated heparin then warfarin — IV heparin is reserved for hemodynamic instability, severe renal impairment, or when thrombolysis or embolectomy is anticipated, none of which apply here
Question 2PulmonaryMedium
A 38-year-old female develops acute bilateral leg swelling and pleuritic chest pain 3 weeks after a long international flight. CT-pulmonary angiogram (CT-PA) shows bilateral segmental pulmonary emboli. Troponin is negative, BNP is 180, and echo shows no right ventricular (RV) strain. She has no provokable risk factors identified. Which of the following is the appropriate minimum duration of anticoagulation?
A1 month
BLifelong anticoagulation
C6 weeks
D3 months
Reveal answer & full explanation
Correct answer: D — 3 months
A1 month
BLifelong anticoagulation
C6 weeks
D3 months✓
Why 3 months is correct
Unprovoked pulmonary embolism (PE): anticoagulate for a minimum of 3 months, then reassess the risk-benefit of extended therapy.
Recurrence risk without anticoagulation is roughly 10% at 1 year and 30–50% at 10 years, so extended anticoagulation is recommended for most unprovoked PEs with low bleeding risk.
Direct oral anticoagulants (DOACs) such as rivaroxaban or apixaban reduce recurrence by 80–90%.
Why the others are wrong
A) 1 month — inadequate duration for unprovoked PE.
C) 6 weeks — inadequate duration for unprovoked PE.
B) Lifelong anticoagulation — not the answer to minimum duration; lifelong therapy may ultimately be chosen after reassessment, but the minimum required course is 3 months.
Additional high-yield points
Risk stratification: low-risk PE (hemodynamically stable, no right ventricular (RV) strain, negative troponin and BNP) — outpatient treatment is appropriate.
High-risk PE (hypotension): systemic thrombolysis or catheter-directed therapy.
Inferior vena cava (IVC) filter: only when anticoagulation is absolutely contraindicated.
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Obesity, advanced age, smoking, long travel (>4 h)
Pathophysiology
Thromboembolus lodges in pulmonary arteries → mechanical obstruction + neurohumoral vasoconstriction → increased pulmonary vascular resistance. Right ventricular afterload rises; severe RV strain can cause hypotension, shock, and death. V/Q mismatch (perfusion of unventilated alveoli initially, then bronchoconstriction) → hypoxemia.
Musculoskeletal chest pain — Reproducible with palpation; normal vitals and oxygenation
Pericarditis/tamponade — Pleuritic pain improved leaning forward, diffuse ST elevation; pericardial effusion on echo
Anxiety/hyperventilation — Diagnosis of exclusion; normal ABG except respiratory alkalosis; no risk factors
Diagnostic workup
Diagnostic criteria
Confirmed PE on imaging. Use validated clinical decision rules: Wells score (low <2, moderate 2-6, high >6) or revised Geneva. PERC rule (8 criteria) can exclude PE in low-probability patients (<15%) without further testing.
Labs
D-dimer — sensitive but not specific; useful to rule out PE in low-probability patients (age-adjusted threshold: age × 10 ng/mL in patients >50)
Troponin and BNP — elevated in RV strain, prognostic (submassive PE)
ABG — hypoxemia, hypocapnia, widened A-a gradient (but normal in up to 20%)
CBC, BMP, INR/PTT before anticoagulation
Thrombophilia workup if unprovoked and young; defer testing until after acute treatment
Imaging
CT pulmonary angiography (CTPA) — gold standard if no contraindication
V/Q scan — alternative if CTPA contraindicated (renal failure, contrast allergy, pregnancy with low CXR yield)
Lower extremity Doppler — supportive when PE imaging contraindicated
Echocardiogram — RV dilation/dysfunction, McConnell sign (akinesia of RV mid-free wall with sparing of apex), pulmonary hypertension; useful for risk stratification not diagnosis
CXR — usually normal or nonspecific; helps exclude alternatives
flowchart TD
A[Suspected PE] --> B{Hemodynamically<br/>unstable?}
B -->|Yes| C[Bedside echo<br/>RV strain?]
C -->|Yes| D[Systemic thrombolysis<br/>or embolectomy]
B -->|No| E[Wells / Geneva<br/>pretest probability]
E -->|Low + PERC negative| F[PE excluded]
E -->|Low/Moderate| G[D-dimer<br/>age-adjusted]
G -->|Negative| F
G -->|Positive| H[CTPA]
E -->|High| H
H -->|Negative| I[Consider alternative dx]
H -->|Positive| J[Anticoagulation<br/>DOAC preferred]
Parenteral options: low-molecular-weight heparin (enoxaparin 1 mg/kg q12h) or unfractionated heparin (preferred if thrombolysis or surgery anticipated, renal failure, hemodynamic instability)
Hemodynamically unstable (massive PE — SBP <90 or vasopressor-dependent): systemic thrombolysis with alteplase 100 mg IV over 2 h
Catheter-directed thrombolysis or surgical/catheter embolectomy if contraindications to systemic thrombolysis or as alternative
Pregnancy: LMWH (does not cross placenta); avoid warfarin and DOACs
Second-line / adjunct
Duration: ≥3 months for provoked PE (transient risk factor); indefinite for unprovoked, recurrent, active malignancy, or persistent risk factors
Cancer-associated VTE: DOACs (apixaban, edoxaban, rivaroxaban) — non-inferior to LMWH (CARAVAGGIO, Hokusai-VTE Cancer trials); LMWH still preferred for GI/GU malignancies due to bleeding risk
IVC filter only if absolute contraindication to anticoagulation; remove when anticoagulation can resume
Submassive PE (RV dysfunction or troponin elevation, but no shock): risk-stratify; consider half-dose tPA or catheter-directed thrombolysis in select patients (PEITHO: thrombolysis reduced hemodynamic decompensation but NOT mortality, with increased major bleeding and stroke)
Outpatient management of low-risk PE (sPESI = 0, normal RV) is appropriate
Complications
Cardiogenic shock, cardiac arrest (PEA most common arrest rhythm)
Chronic thromboembolic pulmonary hypertension (CTEPH) — occurs in ~3% post-PE; treat with pulmonary endarterectomy (curative) or riociguat
Recurrence (~30% over 10 years without secondary prevention)
Bleeding from anticoagulation, including intracranial hemorrhage
Heparin-induced thrombocytopenia (HIT) with platelet drop >50%
PANCE pearls
PERC rule rules out PE without D-dimer in low-pretest-probability patients meeting all 8 criteria: age <50, HR <100, SpO2 >94%, no hemoptysis, no estrogen, no prior VTE, no recent surgery/trauma, no unilateral leg swelling.
Massive PE = hemodynamic instability; submassive = stable BP but RV dysfunction or troponin+; low-risk = stable, no RV strain. Risk-stratification (sPESI, PESI) drives disposition.
ECG findings of severe PE: S1Q3T3 (S in I, Q and inverted T in III), new RBBB, T-wave inversions in anterior leads. Sinus tach remains the most common ECG finding.
Wells criteria + age-adjusted D-dimer (age × 10 ng/mL if >50) safely reduce CTPA imaging in low-probability patients (ADJUST-PE).
DOACs are first-line for most non-pregnant patients with normal renal function; apixaban and rivaroxaban require no parenteral lead-in.
References
CHEST 2021 — Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report (Stevens et al., Chest 2021)
ESC 2019 — 2019 ESC Guidelines for the Diagnosis and Management of Acute Pulmonary Embolism (Konstantinides et al., Eur Heart J 2020)
PEITHO Trial — Fibrinolysis for Patients with Intermediate-Risk Pulmonary Embolism (Meyer et al., NEJM 2014)
ADJUST-PE — Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism (Righini et al., JAMA 2014)
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