Pulmonary Embolism

1. Epidemiology

ICU incidence

Higher due to:Immobilization/Surgery/trauma/Malignancy/Sepsis/Central lines

Mortality

• Untreated PE mortality: ≈30%
• Treated PE mortality: 2–8%
• Massive PE mortality: >25–50%

2. Source of Emboli

3.Ventilation–Perfusion Mismatch

PE causes:

Hypoxemia mechanisms:

• V/Q mismatch
• Atelectasis
• Right-to-left shunt
• Low cardiac output

4. Pathophysiology

PE causes three simultaneous processes:

1. Mechanical obstruction
2. Pulmonary vasoconstriction
3. Right ventricular failure

 Mechanical Obstruction

Pulmonary vascular obstruction leads to:

• ↑ Pulmonary vascular resistance (PVR)
• ↓ Pulmonary blood flow
• ↑ RV afterload

 Pulmonary Vasoconstriction

Mediators released:

• Thromboxane A2
• Serotonin
• Histamine
• Endothelin

Effects:

• Additional increase in pulmonary vascular resistance
• Worsening RV strain

 Right Ventricular Failure 

RV normally pumps against low pressure system.

PE causes:

↑ RV afterload
→ RV dilation
→ RV ischemia
→ ↓ RV contractility

Consequences:

1. Interventricular septal shift
2. ↓ LV filling
3. ↓ cardiac output
4. Hypotension
5. Cardiogenic shock

5. Virchow’s Triad (Risk Factors)

6. Risk Factors

Major

• Major surgery
• Trauma
• Malignancy
• Prior VTE
• Pregnancy/postpartum

Moderate

• OCP use
• Hormone therapy
• Obesity
• Heart failure
• Stroke

ICU specific

• Mechanical ventilation
• Sepsis
• Central venous catheter
• Sedation/paralysis
• ECMO

7. Clinical Presentation

Classic triad (rare)

• Dyspnea
• Chest pain
• Hemoptysis

Common symptoms

Massive PE symptoms

• Hypotension
• Shock
• Syncope
• Cardiac arrest

8. Classification of Pulmonary Embolism-2026

9. Clinical Prediction Scores

Used to estimate pre-test probability.

9.1 Wells Score

Interpretation:

Alternative:

9.2 Geneva Score

Objective variables only:

• Age
• Previous VTE
• Surgery
• HR
• Hemoptysis
• DVT signs

9.3 PERC Rule

Used to rule out PE in low-risk patients.

Criteria:

1. Age <50
2. HR <100
3. O2 sat >94%
4. No hemoptysis
5. No estrogen use
6. No surgery/trauma
7. No prior VTE
8. No DVT signs

If all negative → PE ruled out

10. Laboratory Tests

— D-dimer(High sensitivity)

Cutoff:

• Standard: 500 ng/mL
• Age-adjusted: age × 10 (if >50 yrs)

Use:Best for ruling out PE in low/moderate risk patients.

False positives in:

• Sepsis
• Trauma
• Surgery
• Cancer
• ICU patients

 Cardiac Biomarkers

Troponin

Indicates RV myocardial injury.

Associated with:Worse prognosis

BNP / NT-proBNP

Reflects RV strain

11. Imaging for Pulmonary Embolism

11.1 CT Pulmonary Angiography (CTPA) — Gold Standard

Sensitivity: 83–100%
Specificity: 96–98%

Findings:

• Intraluminal filling defect
• Vessel cutoff
• RV dilation

Secondary signs:Pulmonary infarction/Pleural effusion/Atelectasis

11.2 Ventilation–Perfusion Scan (V/Q Scan)

Used when:

• Contrast allergy
• Renal failure
• Pregnancy

Typical finding:

Mismatch defect

Normal ventilation + absent perfusion.

11.3 Echocardiography

Important in unstable patients.

Findings:

McConnell Sign

• Hypokinetic RV free wall
• Normal RV apex

Highly suggestive of acute PE

11.4 Ultrasound for DVT

Compression ultrasound:

Positive proximal DVT → treat as PE.

12. ECG Findings

Most common—Sinus tachycardia

Classic but rare:

13. Chest X-ray Findings

Often normal.

Possible signs:

 Acute Pulmonary Embolism – Diagnostic Algorithm

 STEP 1: Assess Hemodynamic Stability

➤ Unstable patient? (Shock / SBP <90 / Cardiac arrest)

➡️ YES → HIGH-RISK PE PATHWAY

• Immediate bedside echo
• If RV dysfunction present → treat as PE
• Start reperfusion (don’t delay for CT)
• Systemic thrombolysis
• If stable enough → confirm with CTPA later

➤ NO → Hemodynamically stable

➡️ Proceed to Clinical Probability Assessment

 STEP 2: Clinical Pre-test Probability:

• Wells Score for Pulmonary Embolism
• Revised Geneva Score

Categorization:

• Low probability
• Intermediate probability
• High probability

 STEP 3: Apply PERC (Low-risk patients only)

Use Pulmonary Embolism Rule-out Criteria (PERC)

If ALL PERC negative:➡️ PE ruled out → NO further testing

If ANY positive:➡️ Go to D-dimer

 STEP 4: D-dimer Testing

When to use:Low or Intermediate probability

Interpretation:

• Negative D-dimer → PE ruled out
• Positive → Imaging required

 Age-adjusted D-dimer:

• Age × 10 (if >50 years)

 STEP 5: Imaging

 Gold Standard →CT Pulmonary Angiography (CTPA)

 If CTPA contraindicated:

• Renal failure / contrast allergy / pregnancy

➡️ Use:Ventilation-Perfusion (V/Q) Scan

14. ICU Management of Pulmonary Embolism

 1. INITIAL APPROACH (FIRST 5–10 MIN)

 A. Assess Severity (Use A–E or ESC risk)

• Shock / SBP <90 → HIGH RISK (Category E)
• Stable → risk stratify (A–C)

 B. Immediate Supportive Care

Oxygenation

• Target SpO₂ > 92%
• HFNC / NIV if needed
• Intubation → last resort (can worsen RV failure)

Hemodynamic Support

• Fluids:
• Small bolus (250–500 mL) ONLY if hypovolemic
• Avoid overload (worsens RV dilation)
• Vasopressors:
• Norepinephrine = FIRST LINE
• Add vasopressin if refractory
• Inotropes (if RV failure):
• Dobutamine (low CO states)

Ventilation Strategy (if intubated)

• Low tidal volume
• Avoid high PEEP (↓ venous return)
• Avoid hypercapnia (↑ PVR)

 2. ANTICOAGULATION 

 Start immediately unless contraindicated

 Contraindications (Absolute)

• Active bleeding
• Recent major surgery (high-risk)

A. First-line Options

1. LMWH (Preferred in most stable patients)

• Enoxaparin:1 mg/kg SC BD OR 1.5 mg/kg OD

2. Unfractionated Heparin (UFH)  Preferred in:

• Shock / high-risk PE
• Planned thrombolysis / procedures
• Renal failure

Dose:

• Bolus: 80 U/kg
• Infusion: 18 U/kg/hr (aPTT target 1.5–2.5×)

3. DOACs (Stable patients)

• Apixaban / Rivaroxaban
   No need for heparin bridging (for some regimens)

4. Fondaparinux

• Alternative to LMWH

3. REPERFUSION THERAPY

 A. HIGH-RISK PE (Shock / Category E)

 IMMEDIATE SYSTEMIC THROMBOLYSIS::Do NOT delay thrombolysis for imaging if unstable

• Alteplase (rtPA):
• 100 mg over 2 hrs
  OR
• 50 mg bolus (during cardiac arrest)

 Cardiac Arrest (PE suspected)

• Give bolus thrombolysis during CPR
• Continue CPR ≥60–90 min(Time required for clot lysis and circulation restoration)

Alternative regimens (used in practice):

• 0.6 mg/kg over 15 min (max 50 mg)
   Used in selected cases (lower bleeding risk strategy)

If thrombolysis contraindicated:

• Catheter-directed therapy
• Surgical embolectomy
• VA-ECMO (bridge)

 C. IMPENDING COLLAPSE (Category D)

 Treat aggressively (early thrombolysis)

 Contraindications to Systemic Thrombolysis (PE)

 4. CATHETER-DIRECTED THERAPY (CDT)

Types:

• Catheter thrombolysis (low-dose tPA)
• Mechanical thrombectomy 

Catheter thrombolysis Indications 

✔ Intermediate-high risk PE with:

• RV dysfunction
• Elevated troponin

✔ Clinical deterioration:

• Increasing oxygen need
• Rising lactate
• RV failure progression

✔ Contraindication to systemic thrombolysis

B. MECHANICAL THROMBECTOMY 

Concept: Physical removal of clot WITHOUT thrombolytics

 Types:

1. Aspiration thrombectomy-Large-bore catheter suction

2. Fragmentation-Break clot into smaller pieces

3. Rheolytic systems-High-velocity saline jets

 KEY ADVANTAGE:

 No thrombolysis → NO major bleeding risk

 Evidence:

• FLARE trial (FlowTriever)
• ↓ RV/LV ratio
• Minimal bleeding
• Real-world registries → good safety profile

 Indications 

✔ Intermediate-high risk PE with:

• Bleeding risk (avoid thrombolysis)

✔ Failed thrombolysis

✔ Massive PE when:

• Immediate reperfusion needed
• Thrombolysis contraindicated

 Complications

• Vascular injury
• Hemolysis
• Arrhythmias
• Rare embolization

 5. SURGICAL EMBOLECTOMY

Indications:

• Failed thrombolysis
• Contraindication to thrombolysis
• Massive PE with deterioration

Requires:Cardiothoracic setup

 6. ECMO (ADVANCED SUPPORT)

VA-ECMO Indications:

• Refractory shock
• Cardiac arrest
• Bridge to embolectomy

 7. INFERIOR VENA CAVA (IVC) FILTER

Indications (STRICT):

• Absolute contraindication to anticoagulation
• Recurrent PE despite adequate anticoagulation

 Remove when possible

 15. LONG-TERM ANTICOAGULATION

Preferred Agents

• DOACs preferred over warfarin
• Warfarin if:
• Mechanical valve
• Severe renal failure

Prevention in ICU (VTE Prophylaxis)

Mechanical

• Intermittent pneumatic compression
• Graduated stockings

Pharmacologic

• LMWH
• UFH

Indicated for all ICU patients unless contraindicated.

 Mechanical VTE Prophylaxis

 1. Intermittent Pneumatic Compression (IPC)

cyclically inflate and deflate, mimicking physiologic venous return.

 Mechanism of Action 

1. ↓ Venous stasis (Primary mechanism)

• External compression → ↑ venous blood flow velocity (up to 200–300%)
• Reduces Virchow’s triad: stasis

2. ↑ Endogenous fibrinolysis

• Stimulates tissue plasminogen activator (tPA) release
• ↓ fibrin formation

3. ↓ Venous capacitance

• Promotes venous emptying
• Prevents microthrombi formation

4. Improves endothelial function

• Shear stress → anti-thrombotic endothelial phenotype

 Types of IPC Devices

• PREVENT Trial (NEJM): IPC + pharmacologic prophylaxis did NOT significantly reduce DVT vs anticoagulation alone in ICU
   BUT still used when anticoagulation is contraindicated

Absolute indications:

• Active bleeding
• Recent major surgery (neurosurgery, trauma)
• Severe thrombocytopenia (<50,000)

Relative:

• ICU patients with high VTE risk + temporary bleeding risk

 Contraindications

Complications

• Skin breakdown / pressure ulcers
• Nerve compression (rare)
• Poor compliance (device removal)

 Practical ICU Points

• Must be worn ≥18 hours/day for efficacy
• Ensure correct size and fitting
• Remove periodically for skin inspection
• Combine with anticoagulation if possible (unless contraindicated)

 2. Graduated Compression Stockings (GCS)

 Elastic stockings that provide graded pressure:

• Maximum at ankle → gradually decreases proximally

 Mechanism of Action

1. ↓ Venous stasis-External pressure → reduces venous pooling

2. ↑ Venous return-Enhances deep venous flow velocity

3. ↓ Venous diameter-Improves valve coaptation

 Pressure Gradient 

This gradient is key to effectiveness

• National Institute for Health and Care Excellence (UK):
   Avoid Graduated Compression Stockings alone in stroke patients
  (CLOTS trial → ↑ skin complications, no benefit)

 Indications

• Moderate VTE risk when:
• IPC unavailable/Patient intolerant to IPC
• Adjunct in:Surgical patients (orthopedic, general surgery)

 Contraindications 

Complications

• Skin ulceration (especially elderly)
• Pressure necrosis
• Incorrect sizing → ineffective or harmful

PHARMACOLOGICAL PROPHYLAXIS

1. LMWH (FIRST LINE)

• Enoxaparin 40 mg SC OD

2. UFH

• 5000 IU SC BD/TDS
   Preferred if:
• Renal failure
• Rapid reversal needed

3. Fondaparinux

• Alternative if HIT risk

 WHEN NOT TO GIVE ANTICOAGULATION

• Active bleeding
• Platelets <50k
• Recent hemorrhagic stroke

VTE PROPHYLAXIS IN OPD 

 WHO NEEDS IT?

1. Cancer Patients 

 Follow American Society of Clinical Oncology

Use Khorana Score

 Score ≥2 → prophylaxis indicated

 Drugs in OPD 

• DOACs:
• Apixaban
• Rivaroxaban
• LMWH (if high bleeding risk)

  OTHER OPD INDICATIONS 

A. PRIOR VTE + TEMPORARY RISK FACTOR

• Example:
• Previous DVT + immobilization at home
   Consider prophylaxis

B. PROLONGED IMMOBILITY (HOME)

• Stroke with paralysis
• Frail elderly bedridden

 Consider LMWH

C. PREGNANCY 

Follow Royal College of Obstetricians and Gynaecologists

Indications:

• Previous VTE
• Thrombophilia
• Multiple risk factors

Drug:

• LMWH only (NO DOACs, NO warfarin early)

A. Medical ward  Patients → Padua Prediction Score

 ≥4 = HIGH RISK → GIVE PROPHYLAXIS

B. ICU Patients

 No score required
✔ All ICU patients = high risk by default

C. Surgical Patients → Caprini Score

• 0–1 → low risk
• 2 → moderate
• 3–4 → high
• ≥5 → very high

D. Bleeding Risk Use:IMPROVE bleeding score

Major bleeding risks:

• Platelets <50,000
• Active bleeding
• Recent CNS bleed
• Severe coagulopathy
• Recent major surgery (high-risk)