Pulmonary embolism

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Quick Overview

Pulmonary embolism (PE) is a life-threatening condition requiring rapid diagnosis and treatment. NICE NG158 provides a structured approach using clinical probability assessment (Wells score), D-dimer testing, and imaging to confirm diagnosis, with immediate anticoagulation for most suspected cases. Risk stratification guides safe outpatient management versus admission.

Core Facts & Concepts

Two-Level PE Wells Score

  • PE likely (>4 points): Proceed directly to CTPA
  • PE unlikely (≤4 points): D-dimer first; if positive → CTPA
Clinical FeaturePoints
Clinical signs of DVT3
PE most likely diagnosis3
Heart rate >100 bpm1.5
Immobilisation/surgery (past 4 weeks)1.5
Previous PE/DVT1.5
Haemoptysis1
Malignancy (active/within 6 months)1

D-dimer Limitations

  • High sensitivity (>95%), low specificity (~50%)
  • False positives: pregnancy, malignancy, infection, post-op, elderly, hospitalised patients
  • Age-adjusted threshold: age × 10 μg/L (for age >50 years)
  • 🚩 Never use in "PE likely" patients - delays diagnosis

Figure 1: CT pulmonary angiography showing filling defect in right pulmonary artery

Imaging Selection (NICE NG158)

  • First-line: CTPA - sensitivity 83%, specificity 96%
  • V/Q scan if: contrast allergy, renal impairment (eGFR <30), pregnancy with normal CXR
  • V/Q reported as: normal, low/intermediate/high probability

Immediate Anticoagulation

  • Start before imaging if Wells >4 AND delay >1 hour expected
  • Options: DOAC (apixaban/rivaroxaban), LMWH, or fondaparinux
  • 📊 Contraindications: active bleeding, platelets <50×10⁹/L, recent neurosurgery

Problem-Solving Approach

Step-by-Step Diagnostic Pathway

  1. Calculate two-level Wells score immediately
  2. Wells ≤4 (PE unlikely):
    • Measure D-dimer (age-adjusted if >50 years)
    • Negative D-dimer → PE excluded, no imaging
    • Positive D-dimer → CTPA (or V/Q if contraindicated)
  3. Wells >4 (PE likely):
    • Start anticoagulation if imaging delay >1 hour
    • Arrange immediate CTPA (or V/Q)
  4. PE confirmed → Risk stratify using sPESI

Figure 2: ECG showing sinus tachycardia with S1Q3T3 pattern

🚩 Red Flags for Massive PE

  • Systolic BP <90 mmHg or drop >40 mmHg
  • Syncope, altered consciousness
  • Severe hypoxia (SpO₂ <90%)
  • Cardiac arrest
  • Consider thrombolysis (alteplase 50 mg IV over 1-2 hours)

Analysis Framework

Risk Stratification: Simplified PESI (sPESI)

ParameterPoints if Present
Age >80 years1
Cancer1
Chronic cardiopulmonary disease1
Heart rate ≥110 bpm1
Systolic BP <100 mmHg1
SpO₂ <90%1
  • sPESI = 0: Low risk → outpatient management safe (mortality <1%)
  • sPESI ≥1: Higher risk → consider admission, troponin/BNP, echo

Outpatient Management Criteria (All Must Apply)

  • sPESI = 0
  • No active bleeding/high bleeding risk
  • Adequate social support
  • Normal renal/hepatic function (for DOACs)
  • Follow-up within 24 hours arranged

Visual Aid

CTPA vs V/Q Selection

FactorCTPAV/Q Scan
First-line
Renal impairment (eGFR <30)
Contrast allergy
Pregnancy with normal CXR
AvailabilityWidely availableLimited centres

Key Points Summary

Two-level Wells >4 = PE likely → skip D-dimer, go straight to CTPA; start anticoagulation if imaging delayed >1 hour

Age-adjusted D-dimer (age × 10 μg/L for >50 years) reduces false positives in elderly; never use in "PE likely" patients

CTPA is first-line imaging; V/Q scan reserved for renal impairment, contrast allergy, or pregnancy with normal CXR

sPESI = 0 permits safe outpatient management (mortality <1%); sPESI ≥1 requires admission and further risk assessment

DOACs (apixaban/rivaroxaban) are first-line anticoagulation; no bridging with LMWH needed unlike warfarin

Massive PE (hypotension/arrest) → consider thrombolysis with alteplase 50 mg IV; contraindications include recent surgery/stroke

Common pitfall: Delaying anticoagulation in high-probability PE waiting for imaging - start treatment first if Wells >4 and delay expected

Practice Questions: Pulmonary embolism

Test your understanding with these related questions

A 56-year-old man presents with progressive dyspnea and chest tightness. He works in coal mining. Chest X-ray shows bilateral upper lobe nodules. What is the most likely diagnosis?

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Flashcards: Pulmonary embolism

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Long-term oxygen therapy should not be offered to COPD patients who are _____

TAP TO REVEAL ANSWER

Long-term oxygen therapy should not be offered to COPD patients who are _____

active smokers

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