Pulmonary Embolism

Introduction

Pulmonary embolism (PE) is the presence of a thrombus in the pulmonary arterial circulation. Typically, emboli arise from the lower limb deep venous system but can arise from venous thrombosis in more proximal vessels.

VTE (Venous Thromboembolism) is a term that incorporates both deep venous thrombosis (DVT) and PE (Pulmonary Embolism). It is estimated that VTE are responsible for over 500,000 deaths in Europe each year and is the leading direct cause of maternal death in the UK and Ireland (1).

Risk Factors

Risk factors for thromboembolic disease include;

  • Previous DVT/PE

  • Active Malignancy

  • Obesity

  • Exogenous Oestrogen (e.g. COCP/HRT)

  • Pregnancy

  • Recent surgery (<4 weeks) or immobilisation for >3 days

  • Recent prolonged travel/long haul flight

  • Lower Limb Trauma

  • Thrombophilia (e.g. Factor V Leiden, Protein S/C Deficiency)

 
 

Clinical Features

Signs and symptoms of PE may be vague or non-specific requiring alternative diagnoses to be ruled out concurrently.

Patients with PE may present with;

Signs

Clinical examination may be normal but commonly present signs include

  • Tachycardia

  • Tachypnoea

  • Hypoxia

It is very important to also assess for signs of lower limb DVT

  • Unilateral leg swelling

  • Pitting oedema greater on the affected limb

  • Tenderness along the deep venous system

Symptoms

  • Chest pain, often described as pleuritic

  • Shortness of breath (dyspnoea)

  • Palpitations

  • Haemoptysis

  • Collapse


 
 

Differential Diagnosis

Respiratory

  • Pneumothorax

  • Respiratory tract infection / pneumonia

  • Exacerbation of COPD / asthma

Cardiovascular

  • Acute coronary syndrome

  • Acute aortic dissection

Clinical Decision Rules

PERC.png

PERC Rule

  • Used when the diagnosis pf PE is being considered but the risk is considered low.

  • If a patient is negative in all components of the PERC rule then they can be considered low risk and it may be reasonable to carry out no further work-up for PE

    • If any component of the PERC rule is positive, the patient requires further investigation to assess for PE.

The PERC rule is NOT for use in pregnancy

Wells score.png

Well’s Score

  • A useful clinical decision rule to help assess the probability of a patient having a PE and guiding further investigation in patients where there is a suspicion of PE

  • A low Well’s Score with a negative D Dimer result is considered safe in ruling out PE.

    Not validated in pregnancy or people who inject drugs

Score 0-1 – Low Risk (1.3% prevalence of PE)

Score 2-6 – Moderate Risk (16.2% prevalence of PE)

Score >6 – High Risk (37.5% prevalence of PE)

Clinical Investigions

LITFL ecg.png

Bedside

12 Lead ECG

  • Assess for myocardial ischaemia to rule out ACS

  • Sinus tachycardia is the most common ecg finding in PE

  • S1Q3T3 pattern is rarely seen but if present suggests massive PE as it is a sign of right heart strain

    • Deep S wave in lead I, Q wave in lead III and T wave inversion in lead III

  • RBBB (right bundle branch block) may also be present which also suggests the presence of right heart strain

ABG may show

  • Hypoxaemia

  • Respiratory alkalosis

  • May be normal

ECG from Life in the Fast Lane (2)

blood bottles.jpg

Laboratory

  • FBC, U&E, CRP, Coag screen, Troponin

    • Helpful in ruling out other causes

  • D Dimer

    • Degredation product of fibrin and is raised as a result of fibrinolysis when clotting is taking place

    • Can be raised for a number of other reasons including inflammation, trauma, recent surgery, pregnancy (has not been validated in pregnant patients and therefore should not be used).

    • Sensitive but not specific

      • Sensitivity 96.4%, specificity 52% for PE in the emergency department (3)

      • A negative result is reliable for ruling out VTE in low to intermediate risk patients, but a positive result is not reliable for ruling in VTE

Saddle embolus.png

Radiology

  • Chest x-ray

    • Useful for ruling out other causes (pneumothorax, infection) but is neither sensitive nor specific for diagnosing PE

    • Rarely wedge shaped infarcts may be seen

  • CT Pulmonary Angiogram (CTPA) is the most common diagnostic radiologic test to diagnose PE (4)

  • A V/Q scan is performed less commonly as an alternative to CTPA

  • The safety of CTPA vs V/Q scan in pregnancy has been extensively debated however, 2015 RCOG Guidance preferentially recommends CTPA for diagnosis of PE (5)

Management & Disposition

Initial Assessment & Resuscitation

  • Assess airway, work of breathing and circulation

  • Iv access

  • Continuous cardiac monitoring if vitals abnormal

 
 

Symptomatic Treatment

  • Oxygen if required

    • Target sats to >94%, unless hx of COPD, in which case target 88-92%

  • Analgegsia

    • Paracetamol or ibuprofen

    • Morphine for severe pain

Specific Treatment

Therapeutic anticoagulation

  • Low molecular weight heparin

    • Clexane 1.5mg/kg or

    • Tinzaparin 175units/kg

  • In patients with massive PE who are stable iv unfractionated heparin should be used in case of deterioration and the need for thrombolysis

Haemodynamically unstable patients

  • These patients require input and decision making around their management from senior decision makers in emergency medicine, ICU, coagulation, radiology and medical admitting team

  • They may require thrombolysis

    • Systemic or

    • Catheter directed

Disposition

Patients with suspected PE should be referred to the medical on call team for work-up and investigation

References

1.     Thrombosis Ireland – Irish Statistics- http://thrombosisireland.ie/wp-content/uploads/2017/10/irish-stats.pdf

2.     ECG Changes in Pulmonary Embolism – Life in the Fast Lane - https://litfl.com/ecg-changes-in-pulmonary-embolism/

3.     Dunn K.L. et al Normal D-Dimer levels in emergency department patients suspected of acute pulmonary embolism. J. Am. Coll. Cardiol. 2002. 8(16); 1475-1478

4.     Radiopedia.org - Pulmonary Embolism https://radiopaedia.org/articles/pulmonary-embolism

5.     Thromboembolic Disease in Pregnancy and the Perperium: Acute Management. Royal College of Obstetricians and Gynaecologists https://www.rcog.org.uk/globalassets/documents/guidelines/gtg-37b.pdf

6.     Wells P.S. et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Ann. Intern. Med. 2001. 135(2);98-107

This blog was written by Dr. James Condren and was last updated in October 2020

Before you go have another look at the clinical case and see have your answers to any of the questions changed and if so how?