Pulmonary Embolism (PE) - A Complete Clinical Lecture Note

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Pulmonary Embolism (PE) - A Complete Clinical Lecture Note

Definition:

Pulmonary Embolism (PE) refers to the obstruction of one or more branches of the pulmonary artery by a thrombus, fat embolus, air, or tumor tissue. It is a life-threatening condition that requires immediate diagnosis and treatment.

Etiology and Risk Factors:

  • Deep Vein Thrombosis (DVT) – Most common source (especially from lower limbs)
  • Virchow’s Triad: Hypercoagulability, Venous stasis, Endothelial injury
  • Prolonged immobilization (bed rest, flights)
  • Recent surgery (especially orthopedic procedures)
  • Malignancy
  • Pregnancy and postpartum period
  • Hormonal therapy – oral contraceptives or estrogen
  • Inherited thrombophilias – Factor V Leiden, Protein C/S deficiency
  • Obesity, smoking, older age

Pathophysiology:

The embolus travels through the venous system into the pulmonary circulation, where it blocks blood flow to part of the lungs. This leads to:

  • Ventilation-perfusion mismatch
  • Increased pulmonary vascular resistance
  • Right ventricular strain or failure
  • Reduced cardiac output and possible systemic hypotension

Clinical Features:

  • Sudden onset dyspnea (most common)
  • Pleuritic chest pain
  • Tachypnea and tachycardia
  • Hemoptysis
  • Cyanosis (massive PE)
  • Signs of DVT – calf swelling, tenderness, erythema
  • Syncope or hypotension (massive PE)

Diagnostic Workup:

  • D-Dimer: Elevated in most cases; useful to rule out PE in low-risk patients
  • CT Pulmonary Angiography (CTPA): Gold standard in diagnosis
  • Ventilation/Perfusion (V/Q) scan: Preferred in patients allergic to contrast
  • Compression Ultrasonography: To detect DVT as a source
  • ECG: May show S1Q3T3 pattern, right heart strain
  • Chest X-ray: Often normal but may show Hampton’s hump or Westermark sign
  • ABG: Hypoxemia with respiratory alkalosis

Clinical Prediction Rules:

Wells Score:

  • Clinical signs of DVT – 3 points
  • PE is the most likely diagnosis – 3 points
  • Tachycardia (>100 bpm) – 1.5 points
  • Recent surgery or immobilization – 1.5 points
  • Previous DVT/PE – 1.5 points
  • Hemoptysis – 1 point
  • Malignancy – 1 point

Score ≥4: PE likely | Score <4: PE unlikely

Management:

Initial Stabilization:

  • Oxygen supplementation
  • Hemodynamic support – IV fluids, vasopressors
  • Analgesia and supportive care

Anticoagulation (Mainstay of Therapy):

  • Low molecular weight heparin (LMWH)
  • Unfractionated heparin (especially in renal impairment)
  • Followed by oral anticoagulants (Warfarin, DOACs like Apixaban or Rivaroxaban)
  • Duration: 3–6 months or lifelong depending on recurrence risk

Thrombolytic Therapy:

  • Indicated in massive PE with hemodynamic instability
  • Agents: Alteplase, Tenecteplase

Surgical or Interventional Approaches:

  • Embolectomy – in selected cases
  • Inferior vena cava (IVC) filter – if anticoagulation is contraindicated

Complications:

  • Right heart failure
  • Chronic thromboembolic pulmonary hypertension (CTEPH)
  • Death from cardiovascular collapse

Prevention:

  • Early mobilization post-surgery or during hospitalization
  • Use of compression stockings or pneumatic devices
  • Prophylactic anticoagulation in high-risk individuals

Recent Advances:

  • DOACs have replaced Warfarin in many cases due to fewer interactions and monitoring
  • CTPA with dual-energy and perfusion mapping for better sensitivity
  • Catheter-directed thrombolysis for submassive PE
  • AI-enhanced prediction models and diagnostic tools under development

Key References:

  • Goldhaber SZ, Bounameaux H. Pulmonary embolism. Lancet. 2012.
  • ESC Guidelines on Pulmonary Embolism (2020)
  • ACCP Antithrombotic Therapy Guidelines

 

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