Pulmonary Embolism (PE)

Pulmonary Embolism (PE)

David Ray Velez, MD

Table of Contents

Definition
Physiology
Presentation
Diagnosis
Pulmonary Embolism Severity Index (PESI)
Treatment

Definition

Pulmonary Embolism (PE): Blood Clot Occlusion of the Pulmonary Arteries, Most Often Due to a DVT

Classification

  • High-Risk (Massive) Pulmonary Embolism: Obstructive Shock or Hypotension
  • Intermediate-Risk (Submassive) Pulmonary Embolism: Right Ventricle (RV) Dysfunction or Myocardial Ischemia (MI) but No Shock/Hypotension
    • Intermediate-High Risk: Both Right Ventricle (RV) Dysfunction AND Myocardial Ischemia (MI)
    • Intermediate-Low Risk: Either Right Ventricle (RV) Dysfunction OR Myocardial Ischemia (MI)
  • Low-Risk (Non-Massive) Pulmonary Embolism: No Right Ventricle (RV) Dysfunction, Myocardial Ischemia, or Shock/Hypotension

Location

  • Saddle Pulmonary Embolism: A Large PE Sitting in the Bifurcation of the Pulmonary Artery Where it Splits into the Right and Left Lungs
    • High Mortality Risk
  • Segmental Pulmonary Embolism: Affects the 3rd Division of the Pulmonary Arteries – The Initial Branches Off the Lobar Arteries
  • Subsegmental Pulmonary Embolism (SSPE): Affects the 4th Division of the Pulmonary Arteries

Physiology

Most Common Source: Iliofemoral DVT

Pathophysiology

  • Mechanisms of Impaired Gas Exchange:
    • Ventilation-Perfusion (V:Q) Mismatch Due to Increased Dead Space from Mechanical Obstruction
    • Functional Intrapulmonary Shunting from Inflammation Causing Surfactant Dysfunction and Atelectasis
  • Impaired Gas Exchange Causes Hypoxia
  • Hypoxia Causes Tachycardia and Tachypnea
  • Tachypnea Leads to Hypocapnia and Respiratory Alkalosis

Risk for Sudden Cardiac Arrest and Circulatory Collapse

30% Mortality if Untreated

Presentation

Many are Asymptomatic

Presentation

  • Dyspnea – Most Common Symptom
  • Pleuritic Chest Pain
  • Cough
  • Wheezing
  • Hemoptysis
  • Anxiety

Physical Exam

  • Tachypnea
  • Tachycardia
  • Hypotension
  • Fever
  • Pale Skin

May Also Have Signs/Symptoms of DVT

  • Swelling
  • Pain
  • Warmth
  • Erythema

Diagnosis

Wells Score

  • Used to Predict the Probability of PE Based on History and Physical Exam
  • Factors:
    • Physical Findings of DVT – 3 Points
    • No Better Alternative Diagnosis – 3 Points
    • Tachycardia (HR > 100) – 1.5 Points
    • Immobilization (≥ 3 Days) or Recent Surgery (< 4 Weeks) – 1.5 Points
    • History of DVT/PE – 1.5 Points
    • Hemoptysis – 1 Point
    • Malignancy – 1 Point
  • “Traditional” Wells Interpretation:
    • > 6: High Probability
    • 2-5: Moderate Probability
    • 0-1: Low Probability
  • “Modified” Wells Interpretation:
    • > 4: PE Likely
    • ≤ 4: PE Unlikely

D-Dimer

  • Not Often Used in Surgical Practice
  • Highly Sensitive but Not Specific
  • D-Dimer < 500 ng/mL Likely Excludes the Diagnosis of PE
  • If Low-Moderate Probability of PE: Consider D-Dimer Prior to Imaging
    • Can Possibly Avoid CT if D-Dimer is Low

Arterial Blood Gas (ABG) Findings

  • Hypoxemia
  • Respiratory Alkalosis
  • Widened Alveolar-Arterial Oxygen Gradient

EKG Findings

  • Tachycardia – Most Common EKG Finding
  • S1Q3T3 Pattern (Indicates Right Ventricle Strain) – Rarely Seen
  • T1-4 Inversion

Echocardiography Findings

  • Left Ventricle (LV): Normal Function
  • Right Ventricle (RV): Severely Dilated with Reduced Systolic Function/Wall Hypokinesis
    • Septal Flattening (From RV Pressure Overload)
  • Pulmonary Artery Hypertension
  • McConnell Sign– RV Dysfunction with Akinesia of the Mid-Free Wall but Normal Motion at the Apex
    • Highly Specific for PE
  • D-Sign– Left Ventricle is “D” Shaped Due to Flattening of the Interventricular Septum from Right Ventricular Overload

Definitive Diagnosis

  • Definitive Diagnosis is Based Primarily on Imaging
  • CT Pulmonary Angiogram
    • Gold Standard Diagnostic Test
  • Ventilation-Perfusion Scan
    • Often Used in Women of Child-Bearing Age – Less Breast Radiation (However Has More Fetal Radiation if Pregnant)
  • If Unstable & High Clinical Probability: Empirically Treat Before Definitive Diagnosis

Saddle Pulmonary Embolism on CTA 1

S1Q3T3 on EKG 2

PE POCUS: (A) Significant Right-Sided Distention; (B) “D-Sign” on Short-Axis View with Dilated RV, Flattened Septum (Arrows), and D-Shape of LV 3,4

Pulmonary Embolism Severity Index (PESI)

Used to Predict the 30-Day Morbidity and Mortality for Patients with Diagnosed Pulmonary Embolism

Factors

  • Demographics:
    • Age: +1 Point per Year
    • Male Sex: +10 Points
  • Comorbid Illness:
    • Cancer: +30 Points
    • Heart Failure: +10 Points
    • Chronic Lung Disease: +10 Points
  • Clinical Findings:
    • Altered Mental Status: +60 Points
    • Systolic Blood Pressure (SBP) < 100 mmHg: +30 Points
    • Heart Rate ≥ 110 bpm: +20 Points
    • Respiratory Rate (RR) ≥ 30 bpm: +20 Points
    • Temperature < 36°C: +20 Points
    • Arterial O2 Saturation < 90%: +20 Points

Class/Mortality

PESI ScoreClass30-Day Mortality
0-65I0.0-1.6%
66-85II1.7-3.5%
86-105III3.2-7.1%
106-125IV4.0-11.4%
> 125V10-24.5%

Treatment

Hemodynamically Unstable: Systemic Thrombolytics

  • Consider Catheter-Directed Thrombolysis if High Bleeding Risk
  • Right Ventricular Strain Alone Does Not Require Thrombolysis if Stable
  • May Require Surgical Embolectomy if Thrombolysis is Contraindicated or Fails

Hemodynamically Stable: Anticoagulation

  • Generally Initiated on a Heparin Drip
    • 80 U/kg Bolus with 18 U/Kg/Hr Infusion
    • Goal PTT: 60-90
  • Avoid Intubation if Able – Does Not Resolve Hypoxia and May Cause Hemodynamic Collapse

May Consider Outpatient Treatment for Low-Risk Patients with PESI Class I-II in the Right Clinical Setting – Outside the Scope of Critical Care

Pulmonary Embolism Removed by Thrombectomy 5

References

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  4. Mok KL. Make it SIMPLE: enhanced shock management by focused cardiac ultrasound. J Intensive Care. 2016 Aug 15;4:51. (License: CC BY-4.0)
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