Pulmonary Embolism (PE)

A 62 year old female presents with sudden onset dyspnea, pleuritic chest pain, and palpitations for 6 hours. She underwent hip replacement surgery 2 weeks ago and has been largely immobilized since then. On examination, pulse is 118/min, respiratory rate is 28/min, blood pressure is 104/68 mmHg, and oxygen saturation is 89% on room air. ECG shows sinus tachycardia. D-dimer is elevated. CT pulmonary angiography demonstrates filling defects within the segmental pulmonary arteries. Echocardiography reveals right ventricular dilation. Diagnosis?

Diagnosis is acute pulmonary embolism.

1. Definition

Pulmonary embolism is acute obstruction of pulmonary arteries, usually caused by thrombus originating from proximal deep vein thrombosis.

Pulmonary embolism is part of the venous thromboembolism (VTE) spectrum.

2. Pathophysiology

  1. Embolus obstructs pulmonary arterial blood flow
  2. Increased pulmonary vascular resistance causes right ventricular pressure overload
  3. Right ventricular dilation and dysfunction develop
  4. Interventricular septal shift reduces left ventricular preload
  5. Decreased cardiac output may lead to hypotension and shock
  6. Ventilation-perfusion mismatch causes hypoxemia

3. Risk Factors

  1. Recent surgery
  2. Immobilization
  3. Malignancy
  4. Pregnancy and postpartum state
  5. Estrogen-containing oral contraceptives
  6. Trauma
  7. Previous DVT or PE
  8. Thrombophilia
  9. Obesity
  10. Heart failure

4. Clinical Features

4.1 Common Features

  1. Sudden dyspnea
  2. Pleuritic chest pain
  3. Tachypnea
  4. Tachycardia
  5. Cough
  6. Hemoptysis

4.2 Severe Features

  1. Syncope
  2. Hypotension
  3. Shock
  4. Cyanosis
  5. Sudden cardiac death

4.3 Signs of DVT

  1. Unilateral leg swelling
  2. Calf tenderness
  3. Erythema
  4. Increased calf circumference

5. Diagnosis

5.1 Diagnostic Principle

Assessment of pretest probability is the first step before ordering investigations.

Common clinical prediction tools:

  1. Wells score
  2. Geneva score
  3. Clinical gestalt

5.2 Rule-Out Strategies

PERC Rule

Used in very low-risk patients to avoid unnecessary testing.

D-dimer

  1. Highly sensitive but nonspecific
  2. Used to rule out PE in low or intermediate pretest probability patients
  3. Age-adjusted D-dimer improves specificity in older adults
  4. Not reliable in high-risk patients or patients already on anticoagulation

YEARS Algorithm

Combines clinical assessment with D-dimer thresholds to safely exclude PE in selected patients.

5.3 Imaging

CT Pulmonary Angiography (CTPA)

  1. First-line imaging modality in most patients with suspected PE
  2. Demonstrates intraluminal filling defects in pulmonary arteries

Ventilation-Perfusion (V/Q) Scan

  1. Used when contrast CT is contraindicated
  2. Preferred in severe renal failure or contrast allergy
  3. Commonly used during pregnancy

5.4 Echocardiography

  1. Right ventricular dilation and dysfunction
  2. McConnell sign may be present
  3. Used mainly for risk stratification in unstable patients
  4. Not diagnostic of PE

5.5 ECG Findings

  1. Sinus tachycardia is most common
  2. S1Q3T3 pattern
  3. Right bundle branch block
  4. T wave inversion in right precordial leads

5.6 Arterial Blood Gas

  1. Hypoxemia
  2. Respiratory alkalosis due to hyperventilation
  3. Normal ABG does not exclude PE

6. Risk Stratification

Category A

  • Incidental or asymptomatic PE

Category B

  • Low-risk symptomatic PE without evidence of RV dysfunction

Category C

Symptomatic PE with elevated clinical severity.

Category C1

  • Normal RV function and normal biomarkers

Category C2

  • Either RV dysfunction or elevated biomarkers

Category C3

  • Both RV dysfunction and elevated biomarkers

Category D

  • Incipient cardiopulmonary failure

Category E

  • Cardiopulmonary failure, shock, or persistent hypotension

7. Biomarkers

  1. Troponin elevation suggests RV strain
  2. BNP elevation indicates RV dysfunction
  3. Lactate elevation suggests tissue hypoperfusion and severe disease

8. Management

8.1 Initial Management

  1. Oxygen supplementation
  2. Cardiac and hemodynamic monitoring
  3. Establish IV access
  4. Immediate anticoagulation if suspicion is high and bleeding risk acceptable

8.2 Anticoagulation

Direct Oral Anticoagulants (DOACs)

  1. Preferred long-term therapy in most patients
  2. Common agents include apixaban and rivaroxaban

Low Molecular Weight Heparin (LMWH)

  1. Preferred over UFH when parenteral therapy is needed
  2. Lower risk of heparin-induced thrombocytopenia

Unfractionated Heparin (UFH)

Preferred in:

  1. Hemodynamic instability
  2. Planned thrombolysis or invasive procedures
  3. Severe renal failure
  4. High bleeding risk due to rapid reversibility

8.3 Reperfusion Therapy

Systemic Thrombolysis

  1. Recommended in Category E PE with shock or persistent hypotension
  2. May be considered in selected Category D patients
  3. Not routinely recommended in stable PE due to bleeding risk

8.4 Advanced Therapies

  1. Catheter-directed thrombolysis
  2. Mechanical thrombectomy
  3. Surgical embolectomy
  4. ECMO in refractory cardiogenic shock

8.5 Hemodynamic Support

  1. Careful IV fluid administration
  2. Avoid RV overdistension from excessive fluids
  3. Norepinephrine preferred vasopressor in shock

8.6 Pulmonary Embolism Response Team (PERT)

  1. Recommended in intermediate-high and high-risk PE
  2. Multidisciplinary approach improves management decisions

9. Duration of Anticoagulation

  1. Minimum duration is usually 3 months
  2. Extended therapy considered in unprovoked PE or persistent risk factors
  3. Duration individualized based on bleeding risk and recurrence risk

10. Special Populations

Pregnancy

  1. LMWH is preferred anticoagulant
  2. DOACs are contraindicated during pregnancy

Breastfeeding

  1. LMWH, UFH, and warfarin are acceptable
  2. DOACs are generally avoided

Antiphospholipid Syndrome

  1. Warfarin preferred over DOACs

Cancer-Associated PE

  1. DOACs or LMWH may be used depending on bleeding risk

11. Inferior Vena Cava (IVC) Filters

  1. Not routinely recommended
  2. Consider only if anticoagulation is contraindicated or recurrent PE occurs despite adequate anticoagulation
  3. Associated with increased long-term DVT risk

12. Complications

  1. Recurrent venous thromboembolism
  2. Right ventricular failure
  3. Cardiogenic shock
  4. Chronic thromboembolic pulmonary disease (CTEPD)
  5. Chronic thromboembolic pulmonary hypertension (CTEPH)
  6. Bleeding complications from anticoagulation

13. Follow-Up

  1. Reassess at approximately 3 months
  2. Evaluate need for extended anticoagulation
  3. Assess symptoms and functional limitation at follow-up visits
  4. Persistent dyspnea or exercise intolerance requires evaluation for post-PE syndrome, CTEPD, or CTEPH
  5. Follow-up for at least 1 year is recommended in symptomatic patients

14. Key Clinical Insight

Sudden dyspnea, pleuritic chest pain, tachycardia, hypoxemia, and risk factors such as surgery or immobilization strongly suggest pulmonary embolism

15. Key Exam Points

  1. Most pulmonary emboli arise from proximal lower extremity DVT
  2. Right ventricular failure is the major cause of death
  3. Pretest probability assessment is essential before testing
  4. D-dimer is useful only for ruling out PE in low-risk patients
  5. Use PERC rule and YEARS algorithm when appropriate
  6. CTPA is the first-line imaging modality in most patients
  7. LMWH is preferred over UFH when parenteral anticoagulation is required
  8. Thrombolysis is indicated in Category E PE with shock
  9. DOACs are preferred for long-term anticoagulation in most patients
  10. Persistent dyspnea after PE requires evaluation for CTEPH
By Prabin Duwadee at

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