Pulmonary embolism

See pulmonary embolism in pregnancy for pregnancy specific information.

Background

Pulmonary embolism is an obstruction of one of the branches of the pulmonary arteries by material; typically a thrombus

• Fat, Air, and tumor embolisms can similarly and obstruct a branch of the pulmonary artery, but are not covered in this section
• A pulmonary embolism is on the spectrum of Venous thromboembolism (VTE)
• Most emboli are thought to arise from lower extremity proximal veins (iliac, femoral, and popliteal), whereas a thrombus of the distal veins (calf) resolves spontaneously ⅔ of the time

Pulmonary emboli can be classified according to the level along the pulmonary arterial tree.

Epidemiology

• In the US, approximately 370,000-390,000 PE’s are diagnosed annually
• Mortality
  • Hemodynamically stable (AHA/ACC Class A & B or ESC Low Risk) patients with a PE have a direct mortality of about 1%, however hemodynamically unstable patients mortality ranges from 25-50%
  • For almost one quarter of PE patients, the initial clinical presentation is sudden death

Clinical Features

DVT of right leg

• Diagnosis of PE is challenging, with less than 10% of patients evaluated for a PE ultimately diagnosed with a PE

Symptoms

• Dyspnea at rest or with exertion (75-80%)
• Chest pain (66%)
  • Pleuritic pain, pain that halts respiration, is only seen in 20% of patients
• Cough
• Hemoptysis
• Unilateral calf swelling
• Syncope
  • Syncope is caused by PE <5% of the time

Signs

• Tachycardia (HR>100), Tachypnea (RR>20), Hypoxemia (SpO2<95%) are seen ~50% of the time
• Hypotension (SBP<90) only seen 10% of the time, but largest predictor of mortality
• Unilateral calf tenderness or edema, suggestive of a DVT
• Other signs may include accentuated pulmonic component of second heart sound, JVD, or decreased breath sounds

Differential Diagnosis

Chest pain

Critical

• Acute coronary syndromes (ACS)
  • STEMI
  • Non-STEMI
  • Unstable angina
• Aortic dissection
• Cardiac tamponade
• Coronary artery dissection
• Esophageal perforation (Boerhhaave's syndrome)
• Pulmonary embolism
• Tension pneumothorax

Emergent

• Cholecystitis
• Cocaine-associated chest pain
• Mediastinitis
• Myocardial rupture
• Myocarditis
• Pancreatitis
• Pericarditis
• Pneumothorax

Nonemergent

• Aortic stenosis
• Arthritis
• Asthma exacerbation
• Biliary colic
• Costochondritis
• Esophageal spasm
• Gastroesophageal reflux disease
• Herpes zoster / Postherpetic Neuralgia
• Hypertrophic cardiomyopathy
• Hyperventilation
• Mitral valve prolapse
• Panic attack
• Peptic ulcer disease
• Pleuritis
• Pneumomediastinum
• Pneumonia
• Rib fracture
• Stable angina
• Thoracic outlet syndrome
• Valvular heart disease
• Muscle sprain
• Psychologic / Somatic Chest Pain
• Spinal Root Compression
• Tumor

Acute dyspnea

Emergent

• Pulmonary
  • Airway obstruction
  • Anaphylaxis
  • Angioedema
  • Aspiration
  • Acute respiratory distress syndrome (ARDS)
  • Asthma
  • Cor pulmonale
  • Epiglottitis
  • Inhalation exposure
  • Noncardiogenic pulmonary edema
  • Pneumonia
  • Pneumocystis Pneumonia (PCP)
  • Pulmonary embolism
  • Pulmonary hypertension
  • Tension pneumothorax
  • Idiopathic pulmonary fibrosis acute exacerbation
  • Cystic fibrosis exacerbation
• Cardiac
  • Aortic dissection
  • Cardiac tamponade
  • Cardiogenic pulmonary edema (CHF)
  • Myocardial Infarction
  • Pericarditis
  • Myocarditis
• Other Associated with Normal/↑ Respiratory Effort
  • Abdominal distension
  • Anemia
  • CO Poisoning
  • Salicylate toxicity
  • Diabetic ketoacidosis (DKA)
  • Diaphragm injury
  • Electrolyte abnormalities
  • Flail chest
  • Hypotension
  • Metabolic acidosis
  • Pneumothorax/hemothorax
  • Renal Failure
  • Sepsis
  • Superior vena cava syndrome
  • Toxic ingestion
• Other Associated with ↓ Respiratory Effort
  • Guillain-Barre syndrome
  • Lambert-Eaton Syndrome
  • Multiple sclerosis
  • Myasthenia Gravis
  • Organophosphate toxicity
  • Stroke (Main)
  • Tick paralysis

Non-Emergent

• ALS
• Ascites
• Uncorrected ASD
• Congenital heart disease
• COPD exacerbation
• Deconditioning
• Fever
• Hyperventilation
• Interstitial lung disease
• Neoplasm
• Obesity
• Obstructive sleep apnea
• Panic attack
• Pleural effusion
• Polymyositis
• Porphyria
• Pregnancy
• Rib fracture
• Spontaneous pneumothorax
• Thyroid Disease
• URI
• Vocal cord dysfunction

Workup

ECG of a person with pulmonary embolism, showing sinus tachycardia of approximately 100 beats per minute, large S wave in Lead I, moderate Q wave in Lead III, inverted T wave in Lead III, and inverted T waves in leads V1 and V3.

Assessing Pretest Probability

• A thorough H&P is paramount to assess probability of PE
• Objective scoring systems (wells, revised Geneva) performs similarly to experienced clinician gestalt in assessing pretest probability

Wells Criteria

Clinical Features	Points
Symptoms of DVT (leg swelling and pain with palpation)	3.0
PE as likely as or more likely than an alternative diagnosis	3.0
HR >100 bpm	1.5
Immobilization for >3 consecutive days or surgery in the previous 4 weeks	1.5
Previous DVT or PE	1.5
Hemoptysis	1.0
Malignancy (receiving treatment, treatment stopped within 6 mon, palliative care)	1.0

Two Tier Wells Score

• Score 0-4 = PE Unlikely (12.1% incidence of PE)
  • Check D-dimer
    • If D-dimer positive then obtain CTPA or V/Q scan
    • If D-dimer negative, no further workup needed (0.5% incidence of PE at 3 month follow up)
• Score >4 = PE Likely (37.1% incidence of PE)
  • Obtain CT Pulmonary Angiography or V/Q Scan
• New evidence suggests lower Wells Score with D-dimer <1000 ng/mL is effective at ruling out PE without imaging

If pretest probability of PE is low (<15%)

• Assess PERC Rule criteria,
• If all criteria are "No", very low probability of PE, and no further testing is required
• However, if even 1 criteria is met, proceed as if patient is of intermediate risk

If pretest probability of PE is intermediate (15-50%), or unable to rule out with PERC:

• Perform d-dimer testing and assess YEARS criteria
  • 0 YEARS criteria and d-dimer <1000ng/mL
    • PE excluded
  • ≥1 YEARS criteria and d-dimer <500ng/mL, or age adjusted threshold
    • PE excluded
  • 0 YEARS criteria and d-dimer >1000ng/mL
    • PE not excluded, perform diagnostic imaging
  • ≥1 YEARS criteria and d-dimer ≥500ng/mL, or age adjusted threshold
    • PE not excluded, perform diagnostic imaging

If pretest probability of PE is high (>50%)

• Perform diagnostic imaging

Diagnosis

A large pulmonary embolism at the bifurcation of the pulmonary artery (saddle embolism).

Diagnostic Imaging

• Computed Tomography Pulmonary Artery (CTPA) is the standard and preferred imaging modality
  • If a CTPA is unable to be obtained, a high probability ventilation/perfusion (V/Q) scan is sufficient
    • V/Q Single-photon emission computed tomography (SPECT) is preferred over a planar V/Q scan
    • SPECT combines a non-contrast CT with a planar V/Q and has equivalent sensitivity to CTPA

Additional diagnostic tools

Labs

• Typically obtained to rule out other conditions and to help with risk stratification
• Important to include troponin, BNP, lactate
  • Elevated troponin has a pooled OR of 4.33 for mortality
  • Elevated BNP has a 6.57 odds of short term all cause mortality
  • An elevated lactate leads to 9.05 odds of PE related mortality

Echocardiogram

• Beneficial for short term risk stratification
  • POCUS is an alternative to formal transthoracic echocardiogram (TTE) if TTE is unavailable
• Goal is to evaluate for RV dysfunction as these signs are predictive of mortality
  • RV dilation (RV:LV ratio in diastole >0.9)
  • D sign (Left ventricular septal wall flattening)
  • McConnell's Sign (Mid-RV wall akinesis with hyperdynamic apex)
  • Tricuspid Annular Plane Systolic Excursion (TAPSE), <1.6cm is abnormal

D Sign

Hampton's Hump.

CXR

• Often obtained to rule out other etiologies of chest pain and dyspnea
  • Hampton's Hump
    • Can be confused for a peripheral pneumonia as a wedge shaped peripheral opacity that indicates the presence of a pulmonary infarct
  • Westermark's Sign
    • A focal area of oligemia or reduced blood flow and increased lucency distal to the pulmonary embolism

ECG

• PE's can be associated with ECG changes that indicate acute pulmonary hypertension and right heart strain
• Abnormal in 70% of patients with a PE, however nonspecific
  • Sinus tachycardia
    • Most common arrhythmia associated with PE
  • Symmetric T wave inversions in the anterior leads (V1-V4)
  • McGinn-White S1Q3T3 pattern
  • Incomplete or complete right bundle branch block
  • ST elevations in aVR
  • Atrial fibrillation

Classification

• Both the ESC and the AHA/ACC proposed classification of patients with acute PE into categories based on their potential risk for adverse outcomes
  • ESC 2019 Guidelines: Updated the 2011 AHA/ACC tool by splitting the intermediate or previously referred to as "submassive" patient group into those that present with low-risk features and those that present with high-risk features while maintaining stable hemodynamics.
  • AHA/ACC 2026 Guidelines: A new, 5 tier, non-validated tool using an A-E category system with multiple subcategories is presented in a way to capture higher risk patients who may not have underlying RV dysfunction or cardiac biomarker abnormalities but appear to have a higher risk for adverse outcomes as noted in their proposed D group
• Categorization of PE patients allows for guidance in management decisions

Management

Supportive care

• Oxygen therapy (maintain SpO2 ≥90% unless otherwise indicated)
• Hemodynamic support (e.g. IVF, pressors)
  • Consider gentle fluid challenge of 500ml normal saline bolus to improve cardiac index in select patients
  • Experimental studies suggest that aggressive volume expansion provides little benefit and may worsen RV function in those with acutely elevated RV afterload and acutely increased pulmonary HTN

Anticoagulation

• Always consider bleeding risk when determining risks/benefits of initiating anticoagulation
• Treatment options include any of the following anticoagulations which are indicated for all patients with confirmed PE or high clinical suspicion (do not wait for imaging).

Name	LMWH SC	Unfractionated Heparin	Dabigatran	Rivaroxaban	Apixaban	Coumadin
Initial Dose	Enoxaparin 1mg/kg SC q12h Dalteparin 200 IU/kg SC q24h, max 18,000 IU	80 units/kg bolus; then 18 units/kg/hr continuous infusion	Parenteral anticoagulation for 5-10 days; then 150mg twice daily	15mg twice daily for 3 weeks, then 20mg once daily	10mg twice daily for 1 week, then 5mg twice daily	Cannot be administered alone for acute PE. Usual starting dose 5mg PO
Benefits	1st line for most hemodynamically stable patients Preferred in those with cancer, liver disease, coagulopathy, pregnancy	Short half-life Preferred if rapid reversal is needed (e.g. considering thrombolytics or with bleeding risk/trauma) No need for renal dosing	Noninferior to warfarin in reducing DVT and PE	Preferred if parenteral therapy to be avoided Associated with less bleeding, particularly in elderly patients and those with moderate renal impairment compared to standard treatments	Preferred if parenteral therapy to be avoided or if history of GI bleeding Studies show 16% reduction in VTE related death compared to standard therapy	Preferred in renal disease, history of poor compliance, or history of GI bleed
Contraindications	Severe renal impairment (CrCl <30 mL/min) Patients with morbid obesity or anasarca may have poor absorption	Use with caution in patients >60yo Previous history of HIT	Avoid in CAD and in severe renal impairment	Avoid in hepatic disease (Child-Pugh Class B/C)	Avoid in severe hepatic disease and renal impairment	Temporary hypercoagulable state for approx 5 days
Comments	Dose adjustments may be necessary in obese patients	Check PTT after 6hr; adjust infusion to maintain PTT at 1.5-2.5x control		Consider interactions with CYP3A4 inhibitors (e.g. -azoles)	Consider interactions with CYP3A4 inhibitors	INR target 2.5 Consider many drug-drug interactions with CYP450 inhibitors or inducers

• Duration
  • 3-6 mo, if time limited risk factor (post-op, trauma, estrogen use)
  • 6 mo to life, if idiopathic etiology or recurrent

Subsegmental PE

• Evaluate for proximal DVT in legs with ultrasound
  • If low risk for recurrent VTE: Clinical surveillance recommended over anticoagulation (Level 2C evidence)
  • If high risk for recurrent VTE: anticoagulation recommended over surveillance

Catheter-directed Therapy for intermediate-risk (submassive) PE

• Includes catheter-directed thrombolysis and mechanical thrombus removal without thrombolysis
• Still no large prospective cohort or randomized trial evaluating CDT, so limited evidence recommendations from ACCP 2016 are weak
  • Primary outcome measure in study of 59 patients was improved RV function at 24 hours, but not mortality
• Given broad clinical spectrum of intermediate-risk PE, CDT can be considered in a subset of patients with following characteristics:
  • Intermediate-risk PE with more severe degree of RV dysfunction and positive biomarkers
  • Intermediate-risk PE with severe hypoxemia
  • High-risk (massive) PE with contraindications to systemic thrombolysis
• Complications include major access site bleeding, significant arrhythmias, pulmonary artery dissection, tamponade, worsening hemodynamics

Thrombolysis

• See Thrombolysis for PE

IVC Filter

• Indications
  • anticoagulation contraindicated in patient with PE
  • failure to attain adequate anticoagulation during treatment

Disposition

• Patients with significant clot burden generally require admission for anticoagulation
• Consider discharge in low risk patients with peripheral PE
• Risk stratify which patients can be discharged using HESTIA, sPESI, or PESI scores.

Prognosis

The Pulmonary Embolism Severity Index (PESI)

• PE patients with PESI class I or II seem safe to manage as outpatients.

Prognosis Variable	Points Assigned
Demographics
Age	+Age in years
Male	+10
Comorbid Conditions
Cancer	+30
Heart Failure	+10
Chronic Lung Disease	+10
Clincal Findings
Pulse >110 b/min	+20
sBP < 100	+30
RR > 30	+20
Temp <36 C	+20
AMS	+60
Art O2 Saturation <90%	+20

Risk Class	30-Day Mortality	Total Point Score
I	1.60%	<65
II	3.50%	66-85
III	7.10%	86-105
IV	11.40%	106-125
V	23.90%	>125

Enoxaparin 1 mg/kg SC q12h SC — Preferred in cancer, liver disease, coagulopathy, pregnancy Heparin (UFH) 80 units/kg IV bolus, then 18 units/kg/hr continuous infusion IV drip — Short half-life; preferred if considering thrombolytics or bleeding risk Rivaroxaban 15 mg PO BID x3 weeks, then 20 mg PO daily PO — Preferred if parenteral therapy to be avoided Apixaban 10 mg PO BID x1 week, then 5 mg PO BID PO

See Also

• Pulmonary Embolism in Pregnancy
• IVC Filter
• Cardiac ultrasound

Thrombolytics for pulmonary embolism

• Clinical Page
  • Thrombolysis for PE
• Research summary page: EBQ:Thrombolysis in Pulmonary Embolism Metanalysis
  • PEITHO Trial
  • TOPCOAT Trial
  • MOPETT Trial

Calculators

A-a O₂ Gradient

Alveolar-arterial (A-a) O₂ Gradient

Parameter	Value
Age (years)
FiO₂ (%)
PaCO₂ (mmHg)
PaO₂ (mmHg)
A-a Gradient	mmHg
Expected A-a	mmHg (age-adjusted normal)

Interpretation

Normal A-a gradient ≈ (Age/4) + 4 on room air Elevated A-a gradient suggests: V/Q mismatch, shunt, or diffusion impairment Normal A-a gradient + hypoxia suggests: hypoventilation or low FiO₂

References

Formula: A-a = [FiO₂ × (Patm – PH2O)] – (PaCO₂/0.8) – PaO₂ Kanber GJ, et al. The alveolar-arterial oxygen gradient in young and elderly men during air and oxygen breathing. Am Rev Respir Dis. 1968;97(3):376-381. PMID 5637791.

Wells Score for PE

Wells' PE Score Calculator

Criteria	No	Yes	Points
Clinical signs and symptoms of DVT (leg swelling, pain with palpation)	1		+3.0
PE is #1 diagnosis OR equally likely	1		+3.0
Heart rate >100 bpm	1		+1.5
Immobilization (≥3 days) OR surgery in previous 4 weeks	1		+1.5
Previous objectively diagnosed PE or DVT	1		+1.5
Hemoptysis	1		+1.0
Malignancy (treatment within 6 months or palliative)	1		+1.0
Wells' Score	points

Three-Tier Model

0–1	Low Risk — 1.3% incidence of PE. Consider D-dimer to rule out. Consider PERC rule.
2–6	Moderate Risk — 16.2% incidence of PE. Consider high-sensitivity D-dimer or CTA.
>6	High Risk — 37.5% incidence of PE. Consider CTA. D-dimer not recommended.

Two-Tier Model (Preferred by guidelines)

0–4	PE Unlikely — 12.1% incidence. Consider high-sensitivity D-dimer; if negative, stop workup.
>4	PE Likely — 37.1% incidence. Consider CTA testing.

References

Wells PS, Anderson DR, Rodger M, et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism. Thromb Haemost. 2000;83(3):416-420. PMID 10744147. van Belle A, Büller HR, Huisman MV, et al. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography. JAMA. 2006;295(2):172-179. PMID 16403929.

PERC Rule

PERC Rule Calculator

Criteria	No (0)	Yes (+1)
Age ≥50 years	1
Heart rate ≥100 bpm	1
SpO₂ <95% on room air	1
Unilateral leg swelling	1
Hemoptysis	1
Recent surgery or trauma (within 4 weeks requiring hospitalization)	1
Prior PE or DVT	1
Hormone use (oral contraceptives, HRT, or estrogenic hormones)	1
Positive Criteria	/ 8

Interpretation

Score = 0	PERC Negative — If pre-test probability is ≤15%, PE is effectively ruled out. No further workup needed (sensitivity 97.4%, NPV 99.5%).
Score ≥ 1	PERC Positive — Cannot rule out PE by PERC alone. Consider D-dimer, Wells' score, or CTA based on clinical suspicion.

External Links

• ACEP Clinical Policy: Acute Venous Thromboembolic Disease (Feb 2018)
• MDCalc Simplified PESI
• MDCalc - Well's Criteria for Pulmonary Embolism
• MDCalc - PERC Rule for Pulmonary Embolism
• MDCalc - Geneva Score for Pulmonary Embolism
• MDCalc - PESI - Pulmonary Embolism Severity Index
• MDCalc - Hestia Criteria for Pulmonary Embolism
• MDCalc - HAS-BLED Score for major bleeding risk