Pulmonary Embolism

Pulmonary Embolism

Pulmonary embolism is obstruction of the pulmonary arterial circulation, usually by thrombus originating from the deep veins of the lower extremities or pelvis.

Risk Factors—Virchow’s Triad 

Major

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

Moderate

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

ICU specific(DVT prophylaxis reduces risk in  ~50% cases only!!)

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

Provoked vs unprovoked PE

This distinction becomes extremely important when deciding duration of anticoagulation.

A first PE caused by a major reversible risk factor can generally stop anticoagulation after the initial treatment phase if bleeding/recurrent-risk assessment supports this. In contrast, persistent-risk-factor or unprovoked PE often warrants extended anticoagulation.

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

Clinical Presentation

Classic triad (rare)

• Dyspnea
• Chest pain
• Hemoptysis(from lung tissue necrosis)—it is not contraindication of anticoagulation.

Common symptoms

Anginal chest pain(due to ischemia to the right ventricle).

Low-grade

Examination Look for:

• tachycardia
• tachypnea
• hypoxemia
• hypotension
• raised JVP
• RV heave
• loud P2
• unilateral leg swelling/tenderness

Massive PE symptoms

• Hypotension
• Shock
• Syncope
• Cardiac arrest

Classification of Pulmonary Embolism-AHA 2026

ESC RISK STRATIFICATION OF ACUTE PE

The ESC/ERS approach first asks whether the patient is hemodynamically unstable. If stable, risk is further assessed using PESI/sPESI + RV dysfunction + cardiac biomarkers.

1. HIGH-RISK PE

Hemodynamic instability = high risk

Any of:

➡️ High-risk PE

Treatment: urgent reperfusion + anticoagulation/supportive care.

2. NON-HIGH-RISK PE

Patient is hemodynamically stable.

ESC INTERMEDIATE-RISK CLASSIFICATION

➡️ Requires close monitoring because of risk of early deterioration.

⚠️ Important: A positive troponin alone does not make a patient intermediate-high risk.

3. LOW-RISK PE

Clinical score:PESI I–II or sPESI = 0

AND no features requiring hospitalization.Selected patients may be managed with early discharge/outpatient anticoagulation.

Clinical Prediction Scores

Used to estimate pre-test probability.clinical probability to decide whether D-dimer is appropriate.determine how likely the patient is to have a PE

Wells Score

Interpretation:

Alternative:

Geneva Score

Objective variables only:

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

PERC Rule(Pulmonary Embolism Rule-out Criteria)

Used to rule out PE in low-risk patients.PERC is valid only for patients who present to the emergency department and have llow risk for PE (e.g., Wells score 0-2)

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

Investigations

— D-dimer(High sensitivity-98%)

Cutoff:

• Standard: 500 ug/L or or FEU <0.5 ug/mL
• Age-adjusted For patients ≥50 years: age × 10 μg/L FEU(fibrin-equivalent units)

FEU = ~2(DDU-D-dimer units)—conversion between FEU and DDU is controversial.

• Use:Best for ruling out PE in low/moderate risk patients.(Negative D-dimer with low-moderate pre-test probability: This is generally sufficient to exclude PE)
• False positives in:Sepsis,Trauma,Surgery,Cancer,ICU patients.
• falls over time after acute PE/DVT.

YEARS algorithm

The three YEARS items are:

1. Clinical signs of DVT
2. PE most likely diagnosis
3. Hemoptysis
4. Outpatient presenting to the emergency department

Interpretation

• 0 YEARS criteria→ D-dimer <1000 ng/mL can exclude PE.
• ≥1 YEARS criterion→ D-dimer <500 ng/mL can exclude PE.

Cardiac Biomarkers

• Troponin—Indicates RV myocardial injury.,Associated with:Worse prognosis
• BNP / NT-proBNP—Reflects RV strain

Imaging for Pulmonary Embolism

• HRCT

• Consolidation (necrotic lung tissue).
• Ground-glass opacities (Llocal pulmonary hemorrhage).

• CT Pulmonary Angiography (CTPA) — Gold Standard

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

Findings:

• Intraluminal filling defect(it has other lots of differential diagnosis-like tumour,)
• Vessel cutoff
• RV dilation
• Saddle PE —Clot that straddles the bifurcation of the main pulmonary artery

Secondary signs:Pulmonary infarction/Pleural effusion/Atelectasis

• Ventilation–Perfusion Scan (V/Q Scan)

Used when:

• Contrast allergy
• Renal failure
• Pregnancy

Typical finding:Mismatch defect(Normal ventilation + absent perfusion.)

V/Q SCAN — WHEN IT WORKS BEST

For the highest diagnostic yield, ideally:

• Relatively normal lung parenchyma — e.g., a clear chest X-ray.
• No known chronic thromboembolic disease/PE, which may complicate interpretation.
• Patient can cooperate with the ventilation study and follow instructions.
• Patient is stable enough for transport to nuclear medicine/radiology.

V/Q SCAN — INTERPRETATION

• Echocardiography

• Compression ultrasound: Positive proximal DVT → treatment is same as PE(anticoagulation).

ECG Findings

Most common—Sinus tachycardia

Classic but rare:

Chest X-ray Findings

Often normal.

ABG

• hypoxemia
• hypocapnia
• respiratory alkalosis
• increased A–a gradient.

 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(Systemic thrombolysis) —don’t delay for CT
• If stable enough → confirm with CTPA later

➤ if Hemodynamically stable ➡️ Proceed to Clinical Probability Assessment

 STEP 2: Clinical Pre-test Probability:

• Wells Score for Pulmonary Embolism
• Revised Geneva Score

 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

Use  Age-adjusted D-dimer(if >50 years):Age × 10

 STEP 5: Imaging

 Gold Standard →CT Pulmonary Angiography (CTPA)

 If CTPA contraindicated(Renal failure / contrast allergy / pregnancy)➡️ Use:Ventilation-Perfusion (V/Q) Scan

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(Oxygen is a pulmonary vasodilator)

• 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(pulmonary vasodilation) 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)

C. INHALED PULMONARY VASODILATORS

• May be considered in acute PE with RV dysfunction to reduce RV afterload; the 2026 AHA/ACC guideline supports their use in selected Categories C2–E. 
• Use the agent most readily available. In refractory cases, combining inhaled nitric oxide + epoprostenol may be considered.
• These are adjunctive therapies and should not delay definitive PE treatment (anticoagulation/reperfusion).

Nitroglycerin

• 5 mg nebulized over 15 min, repeat as needed; effect lasts ~30 min.
• A continuous nebulization using 200–400 μg/mL may be used as a temporary bridge until nitric oxide or epoprostenol is available.

Milrinone

• 5 mg nebulized — same dose as nitroglycerin.
• In a peri-arrest patient, 2.5 mg via ETT as a bolus has been described.
• Longer duration than nitroglycerin; may be repeated q3–4 h.

⚠️ Important: The specific nebulized nitroglycerin and milrinone doses are not standardized guideline-based PE regimens and are based largely on limited/experimental evidence. The 2026 guideline supports inhaled pulmonary vasodilators as a class but does not establish these specific dosing protocols. 

Nitric oxide (iNO)

• Intubated / HFNC: start 20 ppm.
• Nasal prongs: 20–50 ppm.
• Gradually wean as clinical status improves.

Epoprostenol

• Start at 50 ng/kg/min.
• Gradually wean as the patient improves.

 2. ANTICOAGULATION 

 Start immediately unless contraindicated

 Contraindications (Absolute)

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

A. First-line Options

1. LMWH (Preferred)

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

2026 guideline generally prefers LMWH over UFH when initial parenteral anticoagulation is required as LMWH has greater efficacy with fewer bleeding complications, while clinical circumstances can favor UFH.

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 

Better not to give admitted patient because its difficult to reverse.

Dabigatran—Requires initial parenteral anticoagulation.Then:150 mg twice daily

When NOT to use DOACs

• Pregnancy
• Severe renal dysfunction
• Antiphospholipid syndrome
• Mechanical heart valve

4. Fondaparinux

• Alternative to LMWH

3. REPERFUSION THERAPY(THROMBOLYSIS)

• Indication —HIGH-RISK PE (Shock / Category E)
• Do NOT delay thrombolysis for imaging if unstable.

BEFORE SYSTEMIC THROMBOLYSIS — ANTICOAGULATION

• If UFH is being used, it is reasonable to stop the infusion before systemic thrombolysis, particularly when there is time to do so safely.
• UFH and thrombolysis can be given in close temporal proximity when necessary. In a patient with high-risk PE who is already anticoagulated and suddenly deteriorates, do NOT delay life-saving thrombolysis simply to allow heparin to “wear off.”
• Alteplase (rtPA):
  • 100 mg (10-20 mg bolus, then remainder over 2 hours) 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)

Tenecteplase: Alternative 

• <60 kg: 30 mg.
• 60-70 kg: 35 mg.
• 70-80 kg: 40 mg.
• 80-90 kg: 45 mg.
• >90 kg: 50 mg.

If thrombolysis contraindicated:

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

After systemic thrombolysis: When should heparin be resumed?

• Resume anticoagulation after thrombolysis once the bleeding risk is acceptable, generally when the aPTT has fallen to <2× the upper limit of normal (commonly <80 seconds, depending on the laboratory).
• If UFH was stopped before alteplase, restart UFH infusion without a bolus once the aPTT is below the above threshold.
• If the patient has ongoing bleeding or a major bleeding concern, delay anticoagulation and reassess frequently.

 Contraindications to Systemic Thrombolysis (PE)

 4. CATHETER-DIRECTED THERAPY (CDT)

Types:

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

A.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

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
• Clot-in-transit which is lying across a patent foramen ovale (PFO)

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

DISCHARGE HOME — LOW-RISK PE

Patients with low-risk PE may be considered for early discharge/outpatient treatment when they are clinically stable and have reliable follow-up.

Best candidates

• sPESI = 0 → identifies a low-risk group.
• HESTIA score = 0 → supports suitability for outpatient treatment.
• No major bleeding risk or significant comorbidity requiring admission.
• Adequate social support, medication access, and reliable follow-up.

⚠️ Important correction: HESTIA should not be described as universally “the primary tool.” Both HESTIA and PESI/sPESI are validated approaches for selecting patients for outpatient management. HESTIA is particularly useful because it incorporates clinical/social factors that may favor hospitalization.

 LONG-TERM ANTICOAGULATION

Preferred Agents

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