Pulmonary Embolism

Maggie Doyle

Background 

  • Definition: obstruction of pulmonary arterial circulation by material that originates elsewhere from the body. The most common etiology is thrombus (e.g., from a lower>upper extremity deep vein clot) but can include tumor, air, or fat. 
  • Risk Factors = Virchow’s Triad 
    • Stasis: immobilization, hospitalization, spinal cord injury, long travel, obesity (due to increased CVP)
    • Hypercoagulable state: malignancy, coagulation disorders, OCPs, nephrotic syndrome, peri-partum, autoimmune disease, tobacco use 
    • Endothelial Injury: surgery, trauma, CVC, recent major infection/sepsis

Presentation

Symptoms 

  • Dyspnea 
  • Pleuritic chest pain 
  • Lower extremity (calf, thigh) pain and/or swelling 
  • Cough, hemoptysis 
  • Syncope (PE is identified in 1 of 6 patients hospitalized for first episode of syncope) 

Examination 

  • Hypoxemia 
  • Sinus tachycardia or arrhythmias 
  • Tachypnea 
  • RV Failure if large PE: elevated JVP, hypotension, syncope, R parasternal heave, accentuated P2, hepatomegaly 
  • Other: S3/S4, pleural friction rub, decreased breath sounds, rales, wheezing, fever

Evaluation 

  • Labs: ABG, troponin, BNP, lactate, PT, PTT 
  • ECG: 
    • Most commonly sinus tachycardia, may see Afib, Aflutter, or another arrhythmia 
    • May be present in setting of large PE: Right axis deviation, RVH, RBBB, RA enlargement, S1Q3T3 (deep S in lead I, deep Q and inverted T in lead III; uncommon and not sensitive), TWI in V1-V3 
  • CXR: Typically normal but may see atelectasis, effusion(s), Hampton hump (wedge-shaped opacity) 
  • TTE: Evaluate for right heart strain, pulmonary vasculature enlargement 
  • Determine Pretest Probability using Modified Wells Criteria: 
    • Wells ≤4 (PE unlikely): D-dimer 
    • Wells >4 (PE likely): CTA Chest PE protocol 
  • Alternate imaging (if CTA PE cannot be performed or is indeterminate) 
    • V/Q scan 
    • Lower extremity ultrasounds 

If hemodynamically unstable and PE suspected, provide hemodynamic support (ie. O2, pressors, etc.) and perform emergent cardiac POCUS 

  • If no RV strain evident on TTE, low likelihood of hemodynamically significant PE. Consider other causes of shock. 
  • Signs of RV strain: D-sign (flattened interventricular septum during systolic) and McConnell’s sign (hypokinetic mid-free wall of RV with preserved contractility of RV apex) 
  • Risk stratification: PE Severity Index (PESI): Predicts 30-day outcome of patients with pulmonary embolism

Management

AHA/ACC PE Clinical Category

Definition / Clinical Features

Initial Management
Category A
(Asymptomatic)
  • Confirmed PE; entirely asymptomatic
  • No hemodynamic compromise
  • No elevated biomarkers
  • No RV dysfunction on imaging
  • Often incidentally detected (e.g., cancer staging)
  • Initiate anticoagulation (DOAC preferred)
  • No advanced therapies indicated
  • Outpatient management with structured follow-up
Category B
(Symptomatic Low-Severity)
  • Symptomatic PE
  • Low clinical severity score: PESI Class I-II, sPESI = 0, or Hestia < 1
  • No elevated cardiac biomarkers
  • Normal RV size and function on imaging
  • Hemodynamically stable
  • Initiate anticoagulation (DOAC preferred)
  • Ensure immediate access to anticoagulation
  • No advanced or escalated therapies
Category C
(Elevated Severity ± RV Involvement)
  • Symptomatic PE with elevated clinical severity score: PESI Class III-V, sPESI ≥ 1, or Hestia ≥ 1
  • C1: High severity score, no RV dysfunction or biomarker elevation
  • C2: High severity score + elevated biomarkers (troponin I/T and/or BNP) OR RV dysfunction on echo/CT
  • C3: High severity score + elevated biomarkers AND RV dysfunction
  • Modifier "R" applied if hypoxemia, tachypnea, or O2 requirement
  • Initiate anticoagulation (LMWH preferred for parenteral; DOAC for oral)
  • Hospitalize for monitoring (oxygenation, BP, HR)
  • PERT consultation recommended for C-E categories
  • Advanced therapies carry uncertain benefit; use only with clinical progression after multidisciplinary PERT deliberation
  • Close monitoring within first 24-72 hrs for C3 patients (risk of deterioration to Cat D/E)
Category D
(Incipient Cardiopulmonary Failure)
  • Pre-failure state: approaching hemodynamic collapse
  • Transient hypotension (SBP < 90 mmHg), or signs of malperfusion: AKI, oliguria, lactic acidosis, altered mental status
  • Worsening RV strain on imaging
  • Escalating O2 requirements
  • Elevated cardiac biomarkers (troponin I/T and BNP) and RV dysfunction on imaging typically present
  • D1-D2 subcategories reflect severity gradations
  • Initiate anticoagulation immediately
  • Hemodynamic support: cautious IVF, vasopressors, inotropes, supplemental O2
  • Urgent PERT activation
  • Advanced therapies (CDT, MT) may be considered for D1-D2 (Class 2b)
  • MT preferred over systemic thrombolysis when bleeding risk is elevated
  • Systemic thrombolysis may be considered if catheter-based therapies unavailable
  • Consider transfer to center with advanced therapy capability (Class 2b)
Category E
(Established Cardiopulmonary Failure)
  • Hemodynamic instability: persistent hypotension (SBP < 90 mmHg), cardiogenic shock, or cardiac arrest
  • Cardiopulmonary failure with persistent hypotension despite resuscitation
  • 30-day mortality exceeds 15%; far Category E
  • Elevated cardiac biomarkers and RV dysfunction on imaging typically present
  • E1: Persistent cardiopulmonary failure
  • Initiate anticoagulation (UFH preferred for potential interventional candidates)
  • Aggressive hemodynamic resuscitation: vasopressors, inotropes, supplemental O2
  • Urgent PERT activation (Class I recommendation)
  • Advanced therapies reasonable for E1 (Class 2a): systemic thrombolysis, CDT, MT, surgical embolectomy
  • MT preferred over systemic thrombolysis when bleeding risk is a concern (Class 2a)
  • VA-ECMO as bridge therapy for refractory cardiopulmonary collapse

Anticoagulation 

  • Initial phase 
    • Unfractionated heparin: preferred for renal dysfunction, extensive clot burden, hemodynamic instability, or any anticipated procedures 
    • LMWH: preferred for pregnant patients 
    • DOAC (Apixaban, Rivaroxaban): appropriate if no anticipated procedures and immediate availability 
      • Require loading doses (10mg BID x 7 days for Apixaban, 15mg BID x 21 days for Rivaroxaban) 
      • Unlike AC in Atrial Fibrillation, there is no data to support AC dose reduction in the initial phase for PE treatment 
  • Maintenance/treatment phase 
    • DOAC 
    • Warfarin (Coumadin): Goal INR 2-3, requires frequent monitoring 
      • Requires bridge with heparin or lovenox 
      • Requires pharmacy consult and establishment with coumadin clinic 
    • LMWH: Used in patients with poor or no oral intake

Duration of Anticoagulation 

  • Major reversible/transient risk factors (surgery, trauma, estrogen therapy, hospital admission): 3- 6 months
  • Idiopathic, unprovoked, or persistent risk factors: 12 months 
  • Major permanent risk factors (cancer, homozygote F5L or prothrombin gene mutation, APLS, protein C/S deficiencies, AT III deficiency): At least 1 year, preferably lifelong. 
  • Recurrent DVT/PE: lifelong (consider etiology) 
  • Chronic Thromboembolic Pulmonary Hypertension (CTEPH): lifelong deflation at the onset of systole (peak of the R-wave on ECG)
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