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 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
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
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)
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
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