Pulmonary Embolism

• Pulmonary embolism is a potentially life-threatening condition caused by the obstruction of one or more pulmonary arteries, commonly due to a thrombus originating from deep vein thrombosis (DVT).
• The formation of a thrombus can be attributed to the key factors that make up Virchow's triad; stasis of blood flow, endothelial injury and hypercoagulability.
• Specific risk factors for PE:

  • Immobility
  • Surgery
  • Malignancy
  • Trauma
  • Pregnancy and the postpartum period
  • Genetic - Factor V Leiden, prothrombin gene mutations, deficiencies in protein C, protein S or antithrombin
  • Comorbidities - heart failure, inflammatory bowel disease, nephrotic syndrome, obesity
• PE pathophysiology:

  1. DVT formation, most commonly in the deep veins of the lower extremities, particularly the calves.
  2. DVT dislodges and becomes an embolus.
  3. The embolus travels through the right side of the heart and becomes lodged in the pulmonary circulation, obstructing blood flow
  4. Obstruction causes vascular resistance, which can cause hypoxia, ischemia and inflammation.
  5. Large or multiple emboli can cause acute right ventricular strain, leading to right sided heart failure, cardiogenic shock and then death.
• PE clinical features:

  • Tachypnoea
  • Fever
  • Tachycardia
  • Hypotension
  • Pleuritic chest pain - worse on inspiration
  • Patient feels breathless
  • Coughing
  • Hemoptysis
  • Dizziness and syncope
• • The risk of PE in suspected patients can be stratified using 2 criteria.
  • First, the Pulmonary Embolism Rule-out Criteria (PERC) score can be used to rule out PE in low risk patients. In order to safely rule out a PE, the patient MUST score 0, and any convincing clinical features need to be absent.
  • If they do qualify for any of the criteria, then you must move on to the Wells' score
  • The Wells' score categorizes patients at risk of PE into low risk or high risk - this can determine how you may initially investigate a patient.
• PERC score criteria:

  • Age >50
  • Heart rate >100
  • Oxygen Saturation on room air <95%
  • Unilateral leg swelling
  • Haemoptysis
  • Recent surgery or trauma
  • Previous PE or DVT
  • Exogenous Oestrogen – oral contraceptives, hormone replacement or other oestrogen hormones
• Wells' Score:

  A) Clinical signs and symptoms of DVT

  B) PE is most likely diagnosis

  C) Heart rate > 100

  D) Immobilization > 3 days OR surgery in previous 4 weeks

  E) Previous DVT or PE

  F) Hemoptysis

  G) Malignancy

  H) 4

  I) 4

  
• ECG changes in PE:

  • Large S wave in lead I
  • Large Q wave in lead III
  • Inverted T wave in lead III

  
• Diagnosing a patient with PE:

  • First take history, perform examination and chest X-ray
  • If PE is still suspected, use Wells' score to assess
  • If PE is likely ( >= 4 points), perform CTPA and give low molecular weight heparin
  • If PE is unlikely (<4 points), arranged D-dimer and only proceed to CTPA if it is positive.
  • If patient has allergy to contrast or renal impairment, then a V/Q scan should be used instead of a CTPA.
• Anticoagulant choice when managing PE:

  • Indications for DOACs - first-line on diagnosis, patients with active cancer
  • Indications for LMWH + vitamin K antagonist - when DOACs are contraindicated, severe renal impairment, antiphospholipid syndrome
• NICE recommends using a 'validated risk stratification tool' to determine the suitability of outpatient treatment for patients with PE - one tool particularly supported is the Pulmonary Embolism Severity Index (PESI) score.
• Length of anticoagulation when managing PE:

  • All patients should receive anticoagulant treatment for at least 3 months
  • If VTE was provoked, you can stop after 3 months (3-6 months in patients with active cancer)
  • If VTE was unprovoked, you treat for 6 months
  • ORBIT score can be used to assess risk of bleeding, which in turn can affect how long patients can receive treatment.
• In patients with massive PE and circulatory failure, then thrombolysis is first-line.
• PE complications:

  • Right ventricular failure and cardiogenic shock
  • Arrhythmias
  • Respiratory failure
  • Pulmonary infarction and necrosis
  • Pleural effusion
  • Pneumothorax
  • Chronic thromboembolic pulmonary hypertension