Introduction to Pulmonary Embolism

This section introduces PE, its clinical presentation, risk assessment scores and diagnostic strategies

In this section:

Introduction

PE is a potential cardiovascular emergency caused by part of a thrombus, usually dislodged from a DVT (subsequently called an embolus), passing into the pulmonary circulation and preventing blood flow to the lungs

  • PE is the most common reason for preventable hospital death
  • Long-term complications include CTEPH, which, although rare, can have serious consequences such as progressive pulmonary hypertension leading to right heart failure,
The pathway of a pulmonary embolus from the lower part of the body
The pathway of a pulmonary embolus from the lower part of the body: inferior vena cava, to right atrium, to right ventricle, to the pulmonary artery. This might eventually obstruct blood flow to the lung. Patients with DVT are at risk of PE, a life-threatening event

Diagnosis

Signs and symptoms

PE is a potentially life-threatening condition, and in severe cases the occurrence of circulatory collapse and cardiac arrest may result in sudden death

  • Early fatality occurs in up to 15% of patients; therefore, rapid diagnosis is crucial
  • The diagnosis of PE, however, may be missed because of its non-specific clinical symptoms
  • Similar to DVT, PE is often asymptomatic, and approximately 20–30% of cases of PE are unprovoked (idiopathic)

Common signs and symptoms of PE:

  • Dyspnoea
  • Pleuritic chest pain
  • Cough
  • Substernal chest pain
  • Fever
  • Haemoptysis
  • Syncope
  • Unilateral leg pain
  • Signs of DVT (unilateral extremity swelling)

Around 80% of patients with PE have signs of DVT, and approximately 50% of patients with proven proximal DVT have an associated PE.

None of the above symptoms is specifically diagnostic of PE. The European Society of Cardiology (ESC) guidelines recommend the use of a stepwise diagnostic algorithm that:

  • Combines several evidence-based diagnostic strategies
  • Stratifies patients according to their risk of early death based on clinical symptoms, as shown in the figures below
  • Has been validated in both the emergency ward and primary care settings
Classification of patients with acute PE based on early mortality risk
Early mortality risk Risk parameters and scores
Cardiogenic shock or hypotension PESI class III–V or sPESI >1a Signs of right ventricular dysfunction on an imaging test Elevated cardiac biomarkers
High + (+)b + (+)b
Intermediate high + Both positive
Intermediate low + Either one (or none) positivec
Low Assessment optional; if assessed, both negativec

aPESI Class III–V: moderate to very high 30-day mortality risk; sPESI ≥1 point(s): high 30-day mortality risk. bNeither calculation of PESI (or sPESI) nor laboratory testing are considered necessary in patients with hypotension or cardiogenic shock. cPatients with PESI Class I–II/sPESI of 0, and elevated cardiac biomarkers/signs of right ventricular dysfunction, are to be considered as intermediate-low risk

High-risk PE is usually suspected if cardiogenic shock and/or hypotension are present. Once stabilized, suspected ‘high-risk’ PE patients can undergo CT pulmonary angiography to confirm or dismiss the diagnosis of PE. If PE is not found to be the cause of haemodynamic instability, other causes (such as ACS) should be investigated.

European Society of Cardiology algorithm for patients with suspected high-risk PE
European Society of Cardiology algorithm for patients with suspected high-risk PE

Adapted from Konstantinides et al. aIncludes cases in which the patient’s condition is so critical that it only allows bedside diagnostic tests; bapart from the diagnosis of RV dysfunction, a bedside transthoracic echocardiogram may, in some cases, directly confirm PE by visualizing mobile thrombi in the right heart chambers; cthrombolysis; alternatively, surgical embolectomy or catheter-directed treatment
RV, right ventricular

Patients categorized as having ‘low-to-intermediate’ risk PE require further risk stratification using clinical judgement or a clinical prediction rule such as the Wells’ score.

  • If the clinical probability of PE is high, a confirmatory CT pulmonary angiography scan should be performed
  • Patients with a ‘low/intermediate’ clinical probability of PE should undergo a D-dimer test before imaging
ESC algorithm for patients with suspected non-high-risk PE
European Society of Cardiology algorithm for patients with suspected non-high-risk PE

Adapted from Konstantinides et al. aTwo alternative classification schemes may be used for clinical probability assessment, i.e. a three-level scheme (clinical probability defined as low, intermediate or high) or a two-level scheme (PE unlikely or PE likely);btreatment refers to anticoagulation treatment for PE; cCT pulmonary angiogram is considered to be diagnostic of PE if it shows PE at the segmental or more proximal level; din case of a negative CT pulmonary angiogram in patients with a high clinical probability, further investigation may be considered before withholding PE-specific treatment

Clinical probability scoring

Scoring systems used in clinical practice include several key risk factors and markers for PE based on patient history and presentation. The Wells’ score is commonly used to predict clinical probability
of PE.

Wells’ score for prediction of PE. A total score >6 indicates a high probability of a PE, a score of
2−6 moderate probability and a score <2 low probability
Parameter Score
Clinically suspected DVT 3
Alternative diagnosis less likely than PE 3
Rapid heart rate 1.5
Immobilization within past 4 weeks 1.5
History of DVT 1.5
Haemoptysis 1
Malignancy 1

Patients with a high likelihood of PE by the Wells’ score should undergo diagnostic imaging. Those with a low/moderate likelihood should have a D-dimer test; if the latter is positive, imaging should be performed.

Diagnostic imaging

CT pulmonary angiography is the preferred method of diagnostic imaging in patients with a clinical risk score indicative of PE because it provides a high resolution image and is as accurate and less invasive compared with pulmonary angiography, the previous ‘gold standard’.

A V/Q scan is another established diagnostic test.

  • Exposes patients to significantly lower levels of radiation than CT pulmonary angiography
  • Preferred in pregnant and young patients or those with severe renal impairment
  • A V/Q scan indicating a high probability of PE provides sufficient evidence for the initiation of treatment but a low probability scan does not rule out PE – further diagnostic tests may be required

Further risk stratification in non-high-risk patients

In non-high-risk patients, further risk stratification is necessary once a PE diagnosis has been confirmed. The ESC guidelines recommend use of the PESI or sPESI score to further risk-stratify patients.

  • Intermediate-risk patients are identified as PESI Class III or higher or sPESI ≥1, and should be further stratified by assessment of right ventricular function and cardiac biomarker levels
    • Patients with normal right ventricular function and/or normal cardiac biomarkers are stratified as intermediate-low risk
    • Patients with evidence of right ventricular dysfunction and elevated cardiac biomarkers (especially elevated cardiac troponin levels) should be classified as intermediate-high risk
    • Intermediate-high-risk patients should be monitored closely for clinical deterioration and may require rescue reperfusion therapy if haemodynamic decompensation occurs

The ESC guidelines recommend that low-risk patients should be considered for early discharge and home treatment providing proper outpatient care and anticoagulant treatment can be provided.

Risk stratification using PESI and sPESI scores
Parameter PESI sPESI
Age Points = age in years If aged >80 years old = 1 point
Male sex +10 points
Cancer +30 points 1 point
Chronic heart failure +10 points 1 point
Chronic pulmonary disease +10 points 1 point
Pulse rate ≥110 beats per minute +20 points 1 point
Systolic blood pressure
<100 mmHg
+30 points 1 point
Respiratory rate
>30 breaths/min
+20 points
Temperature <36°C +20 points
Altered mental status +60 points
Arterial oxyhaemoglobin saturation <90% +20 points 1 point
Class I: ≤65 points
Very low 30-day mortality risk (0–1.6%)
Class II: 66–85 points
Low mortality risk (1.7–3.5%)
0 points = low risk
Low 30-day mortality risk (1.0%)
(95% CI 0–2.1%)
Class III: 86–105 points
Moderate mortality risk
(3.2–7.1%)
Class IV: 106–125 points
High mortality risk
(4.0–11.4%)
Class V: >125 points
Very high mortality risk
(10.0–24.5%)
≥1 point(s) = not low risk
30-day mortality risk
(10.9%)
(95% CI 8.5–13.2%)

CI, confidence interval

Next section: Prevention of Venous Thromboembolism

Approval No.: G.MKT.GM.XA.08.2016.1052

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