Pulmonary Embolism

Quick Answer

Pulmonary embolism (PE) is occlusion of pulmonary arterial circulation by thrombus, leading to impaired gas exchange and potentially right ventricular (RV) failure. Risk stratification determines management: high-risk (massive) PE with hemodynamic instability requires urgent systemic thrombolysis (alteplase 100 mg over 2 hours or 50 mg bolus in cardiac arrest), catheter-directed therapy, surgical embolectomy, or VA-ECMO. Intermediate-risk (submassive) PE with RV dysfunction and elevated biomarkers requires close monitoring and anticoagulation with rescue thrombolysis if deterioration occurs. Low-risk PE is treated with anticoagulation alone (DOAC preferred). D-dimer with age-adjusted cutoffs (age × 10 µg/L if greater than 50 years) improves specificity. CTPA is the gold-standard diagnostic test. RV dysfunction markers include RV/LV ratio greater than 0.9 on echo or CT, elevated troponin, and BNP elevation.

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CICM Exam Focus

The CICM Second Part Examination emphasizes:

1. Risk stratification systems: Wells score, PERC rule, PESI/sPESI, ESC 2019 classification (high/intermediate-high/intermediate-low/low risk)
2. Diagnostic pathway: Clinical probability assessment → D-dimer (age-adjusted) → CTPA → biomarkers and imaging for RV dysfunction
3. Management of massive PE: Immediate thrombolysis indications, dosing regimens, contraindications, rescue therapies (catheter-directed, surgical embolectomy, VA-ECMO)
4. RV dysfunction assessment: Echocardiographic criteria (RV/LV ratio greater than 0.9, McConnell's sign, TAPSE below 16 mm), biomarkers (troponin, BNP/NT-proBNP), CT criteria (RV/LV diameter ratio greater than 1.0)
5. Anticoagulation strategies: DOAC vs LMWH vs UFH selection, duration of therapy, cancer-associated thrombosis, pregnancy considerations
6. Advanced therapies: Catheter-directed thrombolysis (ultrasound-assisted), surgical embolectomy, ECMO indications and complications
7. Complications and sequelae: Chronic thromboembolic pulmonary hypertension (CTEPH), post-PE syndrome, recurrence risk

Common CICM exam scenarios:

• Massive PE in cardiac arrest (ECPR + thrombolysis)
• Submassive PE deteriorating on anticoagulation alone
• PE post-major surgery (bleeding risk vs thrombosis risk)
• Cancer-associated PE management
• PE in pregnancy
• Failed thrombolysis requiring rescue therapy

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Key Points

• High-risk (massive) PE is defined by hemodynamic instability: SBP below 90 mmHg for ≥15 minutes, cardiogenic shock, or cardiac arrest
• Immediate systemic thrombolysis is indicated for high-risk PE unless absolute contraindications: alteplase 100 mg over 2 hours or 50 mg bolus in cardiac arrest scenarios
• RV dysfunction is the critical determinant of risk in hemodynamically stable PE: assess with echo (RV/LV ratio greater than 0.9), CT (RV/LV greater than 1.0), and biomarkers (troponin, BNP)
• PEITHO trial showed fibrinolysis in intermediate-risk PE prevented hemodynamic decompensation (2.6% vs 5.6%) but increased major bleeding (6.3% vs 1.2%) and intracranial hemorrhage (2.0% vs 0.2%); current guidelines recommend against routine thrombolysis in intermediate-risk PE
• DOACs (apixaban, rivaroxaban, edoxaban, dabigatran) are preferred first-line anticoagulants over warfarin for most patients; exceptions include antiphospholipid syndrome, mechanical heart valves, severe renal impairment (CrCl below 30 mL/min), and pregnancy
• Age-adjusted D-dimer cutoff (age × 10 µg/L for patients greater than 50 years) improves specificity from 34% to 46% without loss of sensitivity
• Wells score stratifies pretest probability: ≤4 points = PE unlikely (low risk), greater than 4 points = PE likely (high risk); combined with D-dimer or PERC rule to guide imaging
• PERC rule (8 criteria) can safely exclude PE without D-dimer in low-risk patients if all criteria met: below 1% PE prevalence
• Catheter-directed therapy (ultrasound-assisted low-dose thrombolysis) is an alternative to systemic thrombolysis for intermediate-high risk PE, with lower bleeding risk
• CTEPH develops in 2-4% of PE survivors; screen with echocardiography and/or V/Q scan at 3-6 months post-PE if persistent dyspnea
• IVC filters have limited indications: absolute contraindication to anticoagulation with acute VTE, or recurrent PE despite therapeutic anticoagulation; retrievable filters preferred
• Pregnancy-specific management: CTPA is preferred imaging if CXR abnormal; LMWH is anticoagulant of choice (DOACs contraindicated); avoid warfarin in first trimester due to teratogenicity

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Epidemiology

Incidence and Prevalence

Pulmonary embolism is a common cardiovascular emergency with significant morbidity and mortality.

• Annual incidence: 39-115 per 100,000 population in Western countries
• Hospital mortality:
  • "High-risk (massive) PE: 30-58% without thrombolysis"
  • "Intermediate-risk PE: 3-15%"
  • "Low-risk PE: below 1%"
• Three-month mortality: 15-17.5% overall; reduced to 8.9% with risk-adapted management
• Recurrence rate: 5-10% in first 6 months; 20-30% over 10 years without anticoagulation
• CTEPH incidence: 2-4% of acute PE survivors at 2 years; higher (12-25%) in those with persistent dyspnea

Risk Factors

Strong risk factors (OR greater than 10):

• Major surgery (especially orthopedic, pelvic, neurosurgery)
• Hip or knee arthroplasty
• Major trauma
• Spinal cord injury
• Previous VTE

Moderate risk factors (OR 2-9):

• Malignancy (especially active or undergoing chemotherapy)
• Immobilization greater than 3 days
• Central venous catheters
• Pregnancy and postpartum period (6-fold increased risk)
• Oral contraceptive pill or hormone replacement therapy (2-6 fold)
• Congestive heart failure or respiratory failure
• Inherited thrombophilia (Factor V Leiden, Prothrombin G20210A)

Weak risk factors (OR below 2):

• Advanced age (greater than 60 years)
• Obesity (BMI greater than 30)
• Long-haul travel (greater than 8 hours)
• Varicose veins

Pathophysiology Determinants

The hemodynamic impact of PE depends on:

1. Degree of vascular obstruction: greater than 50% obstruction required for significant hemodynamic effects
2. Cardiopulmonary reserve: Pre-existing cardiopulmonary disease increases risk of decompensation
3. Neurohumoral factors: Serotonin and thromboxane A2 release cause pulmonary vasoconstriction, worsening obstruction

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Pathophysiology

Hemodynamic Consequences

Increased RV Afterload

Mechanism:

• Mechanical obstruction of pulmonary arterial tree increases pulmonary vascular resistance (PVR)
• Neurohumoral vasoconstriction (serotonin, thromboxane A2) further elevates PVR
• RV systolic pressure rises to overcome increased afterload

Consequences:

• RV dilation and wall stress increase
• Tricuspid regurgitation develops (further reduces forward flow)
• Interventricular septum shifts leftward (bowing into LV)
• LV preload and cardiac output decrease

Critical threshold: Normal RV cannot acutely generate systolic pressures greater than 40 mmHg; mean pulmonary artery pressure plateau at 40 mmHg represents maximal RV compensation.

RV Ischemia and Failure

Mechanisms:

1. Reduced RV coronary perfusion:
   • RV perfused during both systole and diastole (unlike LV)
   • Elevated RV systolic pressure exceeds coronary perfusion pressure
   • Diastolic compression from elevated RV end-diastolic pressure
2. Increased oxygen demand:
   • RV wall stress and workload markedly elevated
   • Tachycardia reduces diastolic filling time
3. Hypoxemia: Systemic hypoxemia reduces oxygen delivery to myocardium

Outcome: RV ischemia → regional wall motion abnormalities → further RV dysfunction → cardiogenic shock → cardiac arrest.

McConnell's sign: Akinesis of RV free wall with apical sparing on echocardiography; specific (94%) but insensitive (77%) for acute PE.

Gas Exchange Impairment

V/Q Mismatch

• Dead space ventilation: Ventilated alveoli with reduced/absent perfusion
• Shunt: Atrial-level shunt via patent foramen ovale (PFO) in 20-30% of adults; right-to-left shunting when RA pressure exceeds LA pressure
• Alveolar hypoventilation: Regional bronchoconstriction from loss of surfactant; atelectasis

Hypoxemia

• Mechanisms: V/Q mismatch, shunt (PFO), reduced cardiac output, increased oxygen extraction
• Severity: Directly correlates with degree of vascular obstruction
• Paradoxical embolism: Rare; thrombus crosses PFO causing systemic embolization (stroke, limb ischemia)

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Clinical Presentation

Symptoms

Classic triad (present in below 20% of patients):

• Dyspnea (most common: 73-85%)
• Pleuritic chest pain (44-66%)
• Hemoptysis (13-30%)

Other symptoms:

• Cough (37-50%)
• Syncope or presyncope (10-14%; suggests massive PE)
• Palpitations
• Anxiety or sense of impending doom

Symptoms of DVT:

• Unilateral leg swelling, pain, warmth, erythema (present in ~30% of PE patients)

Signs

Tachypnea: greater than 20 breaths/min (54-70%) Tachycardia: greater than 100 bpm (24-40%) Hypoxemia: SpO2 below 90% on room air (20%) Hypotension: SBP below 90 mmHg (8-10%; defines massive PE) Fever: Low-grade (below 38.5°C) in ~15%

Cardiovascular signs:

• Elevated jugular venous pressure (JVP)
• RV heave (parasternal lift)
• Loud P2 (accentuated pulmonary component of second heart sound)
• Tricuspid regurgitation murmur (pansystolic at left lower sternal border)

Respiratory signs:

• Decreased breath sounds
• Crackles/rales (18%)
• Pleural friction rub (below 5%)

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Risk Stratification

Risk stratification guides diagnostic approach and management intensity. The ESC 2019 guidelines classify PE into four categories.

ESC 2019 Risk Classification

Hemodynamic instability is defined as:

• Cardiac arrest
• Obstructive shock (SBP below 90 mmHg or vasopressor requirement with signs of end-organ hypoperfusion)
• Persistent hypotension (SBP below 90 mmHg for ≥15 min or drop of ≥40 mmHg from baseline)

Clinical Prediction Rules

Wells Score for PE

Stratifies pretest probability of PE to guide imaging and D-dimer use.

Interpretation:

• PE unlikely: ≤4 points (prevalence 5-15%)
• PE likely: greater than 4 points (prevalence 40-65%)

Alternative (3-tier) interpretation:

• Low probability: 0-1 points
• Moderate probability: 2-6 points
• High probability: ≥7 points

Performance: Sensitivity 85%, specificity 63%; validated in emergency department and inpatient settings.

PERC Rule (Pulmonary Embolism Rule-Out Criteria)

Used in low-risk patients (clinical gestalt below 15% pretest probability) to safely rule out PE without D-dimer testing.

Criteria (all 8 must be met):

1. Age below 50 years
2. Heart rate below 100 bpm
3. SpO2 ≥95% on room air
4. No unilateral leg swelling
5. No hemoptysis
6. No recent trauma or surgery (within 4 weeks)
7. No prior PE or DVT
8. No exogenous estrogen use (oral contraceptive, HRT)

Interpretation: If all 8 criteria met, PE can be ruled out (negative predictive value 99.6%); no further testing required.

Limitation: Only validated in low-risk populations; do not use in moderate or high-risk patients.

Pulmonary Embolism Severity Index (PESI)

Predicts 30-day mortality to identify low-risk patients suitable for outpatient management.

PESI Variables:

• Age (1 point per year)
• Male sex (+10 points)
• Cancer (+30)
• Heart failure (+10)
• Chronic lung disease (+10)
• Pulse ≥110 bpm (+20)
• SBP below 100 mmHg (+30)
• Respiratory rate ≥30/min (+20)
• Temperature below 36°C (+20)
• Altered mental status (+60)
• SpO2 below 90% (+20)

Risk Classes:

• Class I: ≤65 points (0.0-1.6% mortality)
• Class II: 66-85 points (1.7-3.5%)
• Class III: 86-105 points (3.2-7.1%)
• Class IV: 106-125 points (4.0-11.4%)
• Class V: greater than 125 points (10.0-24.5%)

Simplified PESI (sPESI)

Easier bedside tool with similar discriminatory performance.

Criteria (1 point each):

1. Age greater than 80 years
2. Cancer
3. Chronic cardiopulmonary disease
4. Heart rate ≥110 bpm
5. SBP below 100 mmHg
6. SpO2 below 90%

Interpretation:

• sPESI 0: Low risk (30-day mortality 1.0%); consider outpatient treatment
• sPESI ≥1: Higher risk (30-day mortality 10.9%); hospitalize

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Investigations

D-Dimer

Mechanism: Degradation product of cross-linked fibrin; elevated in acute thrombosis, but also in infection, inflammation, malignancy, pregnancy, surgery, advanced age.

Performance:

• Sensitivity: 95-98% (high negative predictive value)
• Specificity: 40-45% (many false positives)

Age-adjusted cutoff: Use (age × 10 µg/L) for patients greater than 50 years instead of standard 500 µg/L cutoff.

• Rationale: D-dimer physiologically increases with age
• Impact: Increases specificity from 34% to 46% in patients greater than 50 years without loss in sensitivity (ADJUST-PE study)

Indications:

• Low or moderate pretest probability (Wells ≤4)
• Not indicated if PERC negative or if high pretest probability (proceed directly to imaging)

Limitations:

• Cannot exclude PE in high-risk patients
• Elevated in numerous conditions (pregnancy, infection, malignancy, post-operative state)

CT Pulmonary Angiography (CTPA)

Gold standard for PE diagnosis.

Technique: IV contrast-enhanced multi-detector CT during peak pulmonary arterial enhancement.

Findings:

• Direct signs:
  • Intraluminal filling defect (partial or complete arterial occlusion)
  • "Railway track" sign (contrast outlines thrombus centrally)
  • Complete arterial cutoff
• Indirect signs (suggest RV dysfunction):
  • RV/LV diameter ratio greater than 1.0 (four-chamber view)
  • Interventricular septum bowing into LV
  • Reflux of contrast into IVC and hepatic veins

Performance (PIOPED II study):

• Sensitivity: 83% (90% for main/lobar PE; 68% for subsegmental)
• Specificity: 96%
• Positive predictive value: 92-96% when concordant with clinical probability

Limitations:

• Contraindications: Contrast allergy, renal impairment (CrCl below 30 mL/min), pregnancy (relative)
• Radiation exposure: ~10-15 mSv (equivalent to 3-5 years background radiation)
• Subsegmental PE: Lower sensitivity; clinical significance unclear

Subsegmental PE management: Anticoagulation generally recommended if no contraindications; may consider observation in low-risk patients with good cardiopulmonary reserve and no DVT.

Ventilation-Perfusion (V/Q) Scan

Indications:

• Contraindication to IV contrast (severe renal impairment, anaphylaxis)
• Pregnancy (lower fetal radiation than CTPA: 0.1-0.5 mSv vs 0.2-0.4 mSv)
• Young patients to minimize radiation

Technique: IV technetium-99m macroaggregated albumin (perfusion) + inhaled xenon-133 or technetium-99m aerosol (ventilation).

Interpretation (PIOPED criteria):

• Normal: Excludes PE (NPV 96%)
• High probability: Multiple segmental perfusion defects with normal ventilation (PPV 88%)
• Low or intermediate probability: Requires further testing (40-60% non-diagnostic)

V/Q SPECT: Single-photon emission CT improves diagnostic accuracy over planar imaging (90% vs 70% conclusive results).

Limitation: 30-50% of scans are non-diagnostic (low or intermediate probability).

Echocardiography

Not diagnostic for PE (cannot visualize thrombus in pulmonary arteries), but assesses RV dysfunction and risk stratification.

Indications:

• Hemodynamically unstable patients (bedside assessment)
• Risk stratification in confirmed PE
• Exclusion of alternative diagnoses (cardiac tamponade, aortic dissection, acute MI)

RV dysfunction criteria:

• RV/LV diameter ratio greater than 0.9 (apical four-chamber view; normal below 0.6)
• RV dilation: RV end-diastolic diameter greater than 30 mm
• RV hypokinesis: Reduced RV free wall motion
• McConnell's sign: RV free wall akinesis with apical sparing (specific for PE)
• Tricuspid regurgitation: Severity and estimated RV systolic pressure (RVSP)
• IVC plethora: Dilated IVC with below 50% collapse on inspiration
• Paradoxical septal motion: Interventricular septum bowing into LV during systole
• TAPSE below 16 mm: Tricuspid annular plane systolic excursion (marker of RV systolic function)

Prognostic significance: RV dysfunction on echo increases 30-day mortality 2-fold in normotensive PE.

Thrombus-in-transit: Visualization of thrombus in RA/RV or across PFO; associated with high mortality (25-45%); may indicate need for thrombolysis or surgical embolectomy.

Biomarkers

Cardiac Troponin (cTnI, cTnT, hs-cTnT)

Mechanism: RV ischemia and myocardial injury from increased wall stress.

Prevalence: Elevated in 30-50% of acute PE patients.

Prognostic value:

• Elevated troponin: 30-day mortality 9-16% vs 1-3% if normal
• Odds ratio for mortality: 3.5-6.0
• Identifies intermediate-high risk PE (when combined with RV dysfunction)

Threshold: Any elevation above upper limit of normal (ULN) is prognostically significant; high-sensitivity troponin T greater than 14 pg/mL has 85% sensitivity for adverse outcomes.

Limitations: Not specific for PE; elevated in ACS, myocarditis, sepsis, renal failure.

Natriuretic Peptides (BNP, NT-proBNP)

Mechanism: Released from ventricular myocytes in response to wall stretch; RV dilation increases secretion.

Prevalence: Elevated in 40-50% of acute PE.

Prognostic value:

• BNP greater than 90 pg/mL: Increased risk of mortality and hemodynamic decompensation
• NT-proBNP greater than 500-600 pg/mL: Adverse outcomes more likely
• Combined with troponin: Better risk stratification than either alone

Threshold: BNP greater than 90 pg/mL or NT-proBNP greater than 500 pg/mL.

Limitations: Elevated in heart failure, atrial fibrillation, renal failure, advanced age.

Lower Extremity Venous Ultrasound

Indication: When PE is suspected but CTPA contraindicated or unavailable.

Rationale: Proximal DVT in ~30-50% of PE patients; finding DVT justifies anticoagulation without need for CTPA.

Technique: Compression ultrasound of common femoral, superficial femoral, popliteal veins.

Findings: Non-compressible vein segment indicates thrombus.

Performance: Sensitivity 90-95% for proximal DVT, but only 50% for distal DVT.

Limitation: Negative ultrasound does not exclude PE (50-70% of PE patients have no detectable DVT).

Arterial Blood Gas (ABG)

Findings (non-specific):

• Hypoxemia: PaO2 below 80 mmHg (60% of patients); normal PaO2 does not exclude PE
• Hypocapnia: PaCO2 below 35 mmHg due to hyperventilation (50%)
• Respiratory alkalosis: pH greater than 7.45
• Elevated A-a gradient: greater than 20 mmHg (80% of patients)

Limitation: Non-specific; cannot diagnose or exclude PE. May be normal in up to 20% of PE patients, especially small emboli or those with good cardiopulmonary reserve.

Electrocardiogram (ECG)

Findings (non-specific):

• Sinus tachycardia: Most common (40-70%)
• Right heart strain pattern:
  • "S1Q3T3: S wave in lead I, Q wave in lead III, inverted T wave in lead III (classic but insensitive: 10-20%)"
  • "Right bundle branch block (RBBB): Complete or incomplete (6-10%)"
  • "Right axis deviation: QRS axis greater than 90° (5-10%)"
  • T wave inversion in precordial leads V1-V4 (40-60%; marker of RV strain)
  • "P pulmonale: Peaked P waves in lead II (5%)"
• Atrial arrhythmias: Atrial fibrillation or flutter (5-10%)

Utility: Helps exclude STEMI and identify alternative diagnoses; ECG findings support PE but are not diagnostic.

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Management

Management is stratified by risk category (ESC 2019 classification).

General Supportive Measures

Oxygenation

• Target: SpO2 ≥90% (PaO2 ≥60 mmHg)
• Modalities: Nasal cannula, face mask, high-flow nasal oxygen (HFNO)
• Mechanical ventilation:
  • "Indications: Refractory hypoxemia, respiratory failure, hemodynamic instability"
  • "Strategy: Lung-protective ventilation (tidal volume 6 mL/kg IBW, plateau pressure below 30 cmH2O)"
  • "Caution: Positive pressure ventilation reduces venous return → further decreases RV preload and cardiac output → can worsen shock"
  • "Preoxygenation before intubation: Critical; desaturation during apnea can precipitate cardiac arrest"

Hemodynamic Support

Fluid resuscitation:

• Caution: Overzealous fluids can worsen RV function (RV dilation → septal shift → reduced LV filling → reduced CO)
• Strategy: Judicious fluid bolus (250-500 mL crystalloid); monitor for worsening hemodynamics
• Goal: Maintain adequate preload without RV overdistension

Vasopressors (for hemodynamic instability):

• Norepinephrine: First-line (increases SVR and maintains coronary perfusion pressure)
  • "Dose: 0.05-0.5 mcg/kg/min"
• Dobutamine: Inotropic support if low cardiac output despite adequate preload
  • "Dose: 2.5-10 mcg/kg/min"
  • "Risk: Can worsen hypotension (vasodilatory effects); combine with norepinephrine"
• Vasopressin: Alternative vasopressor if refractory shock
  • "Dose: 0.03-0.04 units/min"

Avoid: Aggressive volume loading (can worsen RV failure).

Anticoagulation

Initiate immediately (within 24 hours) unless contraindications, even before diagnostic confirmation in high-probability patients.

Direct Oral Anticoagulants (DOACs)

Preferred first-line in most patients (ESC 2019, CHEST 2016 guidelines).

Advantages over warfarin:

• No routine monitoring required
• Rapid onset (2-4 hours)
• Fewer drug-drug and drug-food interactions
• Lower risk of intracranial hemorrhage (RR 0.4-0.6)
• Non-inferior efficacy (AMPLIFY, EINSTEIN-PE, HOKUSAI-VTE trials)

Contraindications:

• Severe renal impairment (CrCl below 30 mL/min for most; below 15 for apixaban)
• Mechanical heart valves
• Antiphospholipid syndrome (warfarin preferred)
• Pregnancy and breastfeeding
• Active bleeding

Reversal agents:

• Idarucizumab (Praxbind): Dabigatran reversal (5 g IV)
• Andexanet alfa (Andexxa): Factor Xa inhibitor reversal (apixaban, rivaroxaban)

Low-Molecular-Weight Heparin (LMWH)

Indications:

• Cancer-associated thrombosis (preferred over DOAC; reduced recurrence)
• Pregnancy (DOACs contraindicated)
• Severe renal impairment (CrCl below 30 mL/min)
• Bridge to warfarin (when DOACs contraindicated)

Dosing (enoxaparin):

• 1 mg/kg SC every 12 hours (preferred)
• 1.5 mg/kg SC once daily (alternative)

Renal adjustment: Reduce dose by 50% if CrCl below 30 mL/min (e.g., enoxaparin 1 mg/kg once daily).

Monitoring: Generally not required; anti-Xa levels if obesity (BMI greater than 40), renal impairment, pregnancy, or bleeding.

Reversal: Protamine sulfate (1 mg per 100 units of LMWH within 8 hours; partial reversal only ~60%).

Unfractionated Heparin (UFH)

Indications:

• High-risk (massive) PE
• Severe renal impairment (CrCl below 15 mL/min)
• High bleeding risk (short half-life allows rapid reversal)
• Peri-procedural (catheter-directed therapy, surgical embolectomy)
• Hemodynamically unstable patients (better control and titrability)

Dosing:

• Bolus: 80 units/kg IV (or 5,000 units)
• Infusion: 18 units/kg/h (initial rate ~1,300 units/h)
• Target aPTT: 1.5-2.5 × control (60-80 seconds)

Monitoring: aPTT every 6 hours until therapeutic, then daily.

Reversal: Protamine sulfate (1 mg per 100 units of heparin; complete reversal).

Warfarin

Indications:

• Antiphospholipid syndrome (DOACs less effective)
• Mechanical heart valves
• Patient preference or cost considerations

Dosing:

• Initial: 5-10 mg PO daily
• Overlap with LMWH or UFH for ≥5 days and until INR 2-3 on 2 consecutive days
• Target INR: 2-3

Monitoring: INR daily initially, then weekly, then monthly once stable.

Drug interactions: Extensive; avoid NSAIDs, antibiotics (fluoroquinolones, macrolides, metronidazole), antifungals, amiodarone.

Reversal:

• Vitamin K: 5-10 mg IV/PO (onset 12-24 hours)
• Prothrombin complex concentrate (PCC): Immediate reversal (25-50 units/kg)

Duration of Anticoagulation

Annual bleeding risk on anticoagulation: 1-3% major bleeding; 0.5% fatal bleeding.

Risk-benefit reassessment: At 3-6 months and annually; consider HAS-BLED score for bleeding risk.

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Reperfusion Therapy

Systemic Thrombolysis

Indications

Absolute indication (Class I recommendation):

• High-risk (massive) PE: Hemodynamic instability (SBP below 90 mmHg, shock, cardiac arrest)

Conditional indication (Class IIb recommendation):

• Intermediate-high risk PE: Hemodynamically stable but deteriorating (worsening RV dysfunction, rising troponin, increased oxygen requirements)

Not recommended:

• Intermediate-low risk or low-risk PE: Risk of major bleeding outweighs benefit (PEITHO trial)

Contraindications

Absolute:

• Prior intracranial hemorrhage
• Known structural intracranial vascular lesion (AVM, aneurysm)
• Known malignant intracranial neoplasm
• Ischemic stroke within 3 months
• Suspected aortic dissection
• Active bleeding or bleeding diathesis (except menses)
• Recent brain or spinal surgery
• Recent head trauma with fracture or brain injury

Relative:

• Age greater than 75 years (increased ICH risk)
• Current anticoagulation (INR greater than 1.7)
• Pregnancy or within 1 week postpartum
• Non-compressible vascular puncture
• Traumatic or prolonged CPR (greater than 10 min)
• Recent internal bleeding (within 2-4 weeks)
• Recent major surgery (within 3 weeks)
• History of chronic, severe, poorly controlled hypertension
• Ischemic stroke greater than 3 months ago
• Dementia or intracranial pathology not covered above
• Platelet count below 100,000/mm³

Thrombolytic Regimens

Alteplase (rtPA) – Most common:

• Standard dose: 100 mg IV over 2 hours
• Accelerated dose (for cardiac arrest/ECPR):
  • 50 mg IV bolus, or
  • 0.6 mg/kg bolus (max 50 mg)

Tenecteplase (TNK):

• Dose: Weight-based single bolus
  • below 60 kg: 30 mg
  • 60-69 kg: 35 mg
  • 70-79 kg: 40 mg
  • 80-89 kg: 45 mg
  • ≥90 kg: 50 mg
• Advantage: Single bolus; easier administration

Streptokinase (less commonly used):

• Dose: 250,000 units IV over 30 min, then 100,000 units/h × 12-24 hours
• Disadvantage: Longer infusion; antigenic (allergic reactions); less fibrin-specific

Urokinase (rarely used):

• Dose: 4,400 units/kg bolus, then 4,400 units/kg/h × 12-24 hours

Concomitant Anticoagulation

• UFH: Typically paused during thrombolytic infusion; resume without bolus once aPTT below 80 seconds (typically 3-4 hours after completion)
• LMWH: Hold for 12-24 hours after thrombolysis, then resume therapeutic dose
• DOACs: Avoid for 24-48 hours after thrombolysis

Monitoring and Complications

Monitoring:

• Continuous cardiac monitoring
• Neurological checks every 1 hour for 24 hours (to detect intracranial hemorrhage)
• Serial hemoglobin, platelet count
• Fibrinogen levels (expect decrease; below 100 mg/dL suggests systemic fibrinolysis)

Major complications:

1. Major bleeding: 6-13% (PEITHO: 6.3% vs 1.2% with anticoagulation alone)
   • Intracranial hemorrhage: 1-3% (PEITHO: 2.0% vs 0.2%)
   • GI bleeding: 2-3%
   • Retroperitoneal bleeding: 1-2%
2. Hemodynamic improvement: Typically within 1-2 hours; maximal at 12-24 hours
3. Recurrent PE: 1-2% despite anticoagulation

Management of bleeding:

• Stop thrombolytic immediately
• Reverse anticoagulation:
  • "UFH: Protamine 1 mg per 100 units (max 50 mg)"
  • "LMWH: Protamine (partial reversal only)"
• Replace fibrinogen: Cryoprecipitate (10 units) or fibrinogen concentrate
• Tranexamic acid: 1 g IV over 10 min (antifibrinolytic)
• Blood products: Packed RBCs, FFP, platelets as needed
• Surgical/interventional control: If accessible bleeding site

Evidence

MAPPET-3 trial (2002, PMID: 11907286):

• 256 patients with submassive PE (RV dysfunction on echo)
• Alteplase 100 mg + heparin vs heparin alone
• Results: Death or escalation of treatment: 11% vs 25% (p=0.006)
• Conclusion: Thrombolysis reduces clinical deterioration in submassive PE

PEITHO trial (2014, PMID: 24716680):

• 1,005 patients with intermediate-risk PE
• Tenecteplase + heparin vs placebo + heparin
• Results:
  • "Primary outcome (death or hemodynamic collapse at 7 days): 2.6% vs 5.6% (p=0.02)"
  • "Major extracranial bleed: 6.3% vs 1.2% (pbelow 0.001)"
  • "Intracranial hemorrhage: 2.0% vs 0.2% (p=0.003)"
  • "All-cause mortality: No difference (1.2% vs 1.8%)"
• Conclusion: Tenecteplase prevents hemodynamic decompensation but increases bleeding risk; not recommended for routine use in intermediate-risk PE

Meta-analysis (Chatterjee et al., 2014, PMID: 24935657):

• 16 trials, 2,115 patients
• Results: Thrombolysis reduced mortality (OR 0.53) but increased major bleeding (OR 2.73) and intracranial hemorrhage (OR 4.63)
• Conclusion: Reserve thrombolysis for high-risk PE; unfavorable risk-benefit in intermediate-risk PE

Catheter-Directed Therapy (CDT)

Indications:

• Intermediate-high risk PE with contraindication to systemic thrombolysis
• High-risk PE with contraindication to systemic thrombolysis or failed systemic thrombolysis
• Bridge to definitive therapy (surgical embolectomy, ECMO)

Techniques:

1. Ultrasound-assisted catheter-directed thrombolysis (USAT):
   • Device: EkoSonic catheter (EKOS)
   • Mechanism: Ultrasound energy disrupts fibrin cross-links, enhancing thrombolytic penetration
   • Alteplase dose: 10-24 mg over 6-15 hours (much lower than systemic dose)
2. Catheter-directed thrombolysis (without ultrasound):
   • Alteplase: 1-2 mg/h × 12-24 hours
3. Mechanical thrombectomy (aspiration, rheolytic):
   • Devices: FlowTriever, AngioVac, AngioJet
   • Mechanism: Suction/fragmentation of thrombus

Advantages:

• Lower thrombolytic dose: Reduced bleeding risk (major bleeding 10% vs 20% with systemic lysis)
• Faster symptom relief: Direct delivery to clot
• Lower ICH risk: 0-1% vs 2-3% with systemic lysis

Complications:

• Bleeding (vascular access site, hemoptysis): 5-10%
• Pulmonary hemorrhage: 2-3%
• Cardiac perforation/tamponade: below 1%
• Arrhythmias: 3-5%

Evidence:

• ULTIMA trial (2014, PMID: 24226805): 59 patients with intermediate-risk PE; USAT vs heparin alone; USAT improved RV function at 24 hours (RV/LV ratio reduction)
• SEATTLE II (2015, PMID: 26315743): 150 patients; USAT reduced RV/LV ratio from 1.55 to 1.13 at 48 hours; major bleeding 10%

Surgical Pulmonary Embolectomy

Indications:

• High-risk PE with:
  • Contraindication to thrombolysis
  • Failed thrombolysis
  • Free-floating RA/RV thrombus
  • PFO with paradoxical embolism risk
  • Massive PE in cardiac arrest (ECPR candidate)

Procedure:

• Median sternotomy
• Cardiopulmonary bypass
• Bilateral pulmonary arteriotomies
• Manual extraction of thrombus

Outcomes:

• Operative mortality: 6-30% (historically 30-50%; improved with modern techniques and patient selection)
• Best outcomes: Performed at high-volume centers with experienced surgical teams
• Predictors of mortality: Pre-op cardiac arrest, prolonged shock, delayed surgery

Evidence:

• Observational data show mortality 6-10% in specialized centers vs 30-50% in low-volume centers
• No RCT comparing embolectomy vs thrombolysis

Extracorporeal Membrane Oxygenation (ECMO)

Indication:

• Massive PE with cardiac arrest or refractory cardiogenic shock
• Bridge to recovery (while thrombolysis takes effect)
• Bridge to definitive therapy (surgical embolectomy, catheter-directed therapy)

Configuration:

• Veno-arterial (VA) ECMO: Provides both respiratory and hemodynamic support
  • "Cannulation: Femoral vein (drainage) → femoral artery (return)"
  • "Flow rates: 3-5 L/min"

Duration: Typically 1-7 days; wean as RV function recovers.

Complications:

• Bleeding (requiring transfusion): 40-70%
• Limb ischemia: 10-20% (distal perfusion cannula reduces risk)
• Infection: 10-15%
• Stroke: 5-10%
• Harlequin syndrome (differential hypoxemia): Occurs with peripheral VA-ECMO if native cardiac output recovers but LV ejects deoxygenated blood

Outcomes:

• Survival to discharge: 50-70% in experienced centers (vs greater than 90% mortality without ECMO in cardiac arrest from massive PE)
• Predictors of survival: Shorter CPR duration (below 60 min), witnessed arrest, initial shockable rhythm, younger age

Evidence:

• Pasrija et al. (2018, PMID: 29129541): 60 patients with massive PE on VA-ECMO; 57% survival; median ECMO duration 4 days
• Weinberg et al. (2017, PMID: 28219105): Review of ECMO for PE; survival 50-70% with ECMO vs 10% without

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Special Populations

Cancer-Associated Thrombosis (CAT)

Incidence: 4-20% of cancer patients; 20-30% of all VTE events occur in cancer patients.

High-risk malignancies: Pancreatic, gastric, brain, ovarian, lung, hematologic.

Pathophysiology: Hypercoagulability (tissue factor, mucins), venous stasis, endothelial injury (chemotherapy).

Anticoagulation:

• First-line: LMWH (enoxaparin 1 mg/kg BID or dalteparin 200 units/kg daily)
  • "Advantage: Reduced VTE recurrence vs warfarin (9% vs 17% at 6 months)"
• Alternative: Edoxaban or rivaroxaban (non-inferior to LMWH)
  • "Exception: GI or genitourinary malignancies (higher bleeding risk with DOACs; prefer LMWH)"
• Duration: Minimum 3-6 months; indefinite if active cancer or ongoing chemotherapy

Monitoring: Platelet count (thrombocytopenia from chemotherapy; hold if below 50,000/mm³).

Pregnancy

Incidence: 1-2 per 1,000 pregnancies; 6-fold increased VTE risk vs non-pregnant.

Diagnostic challenges:

• D-dimer physiologically elevated in pregnancy (not useful)
• Radiation concerns with CTPA and V/Q scan

Imaging approach:

1. Compression ultrasound of legs first (if positive, no further imaging needed)
2. If negative and high suspicion:
   • V/Q scan (preferred if CXR normal; lower fetal radiation: 0.1 mSv vs 0.2-0.4 mSv with CTPA)
   • CTPA (if CXR abnormal or V/Q non-diagnostic; higher maternal breast radiation)

Anticoagulation:

• LMWH: Treatment of choice (enoxaparin 1 mg/kg BID)
  • Does not cross placenta
  • Safe in all trimesters and during breastfeeding
  • Monitor anti-Xa levels (target 0.6-1.0 units/mL at 4 hours post-dose)
• Warfarin: Contraindicated (teratogenic in first trimester; fetal bleeding risk)
• DOACs: Contraindicated (cross placenta; limited safety data)

Duration: Continue throughout pregnancy and ≥6 weeks postpartum (minimum total duration 3 months).

Delivery planning:

• Stop LMWH 24 hours before planned delivery (minimize epidural hematoma risk)
• Resume 6-12 hours post-delivery (vaginal) or 12-24 hours (C-section)

Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

Definition: Precapillary pulmonary hypertension (mPAP ≥25 mmHg) due to chronic organized thrombus in pulmonary arteries.

Incidence: 2-4% of acute PE survivors at 2 years; up to 12-25% in those with persistent dyspnea.

Risk factors: Recurrent PE, large thrombus burden, unprovoked PE, splenectomy, infected pacemaker.

Symptoms: Progressive dyspnea, reduced exercise tolerance, signs of RV failure.

Screening:

• Echocardiography at 3-6 months post-PE (assess RVSP, RV function)
• V/Q scan if elevated RVSP or persistent symptoms (more sensitive than CTPA for chronic thrombus)
• Right heart catheterization if V/Q abnormal (confirms pulmonary hypertension)

Treatment:

1. Pulmonary endarterectomy (PEA): Curative; only treatment to improve survival
   • Candidacy: Surgically accessible thrombus (main, lobar, segmental arteries)
   • Outcomes: 5-year survival 80-90% post-PEA
2. Balloon pulmonary angioplasty (BPA): For distal/inoperable disease
3. Medical therapy: Riociguat (soluble guanylate cyclase stimulator) if inoperable or residual PH post-PEA
4. Lifelong anticoagulation: To prevent recurrence

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Prognosis and Follow-Up

Short-Term Outcomes

30-day mortality:

• High-risk PE: 15-30% (without reperfusion therapy: 30-58%)
• Intermediate-high risk PE: 3-15%
• Intermediate-low risk PE: 3-15%
• Low-risk PE: below 1%

Predictors of mortality:

• Hemodynamic instability
• RV dysfunction (echo, CT, biomarkers)
• Elevated troponin and BNP
• Advanced age (greater than 70 years)
• Comorbidities (cancer, heart failure, COPD)

Long-Term Outcomes

Recurrence:

• Off anticoagulation: 10% at 1 year; 30% at 5 years (unprovoked PE)
• On anticoagulation: 1-2% per year

Chronic sequelae:

• CTEPH: 2-4% at 2 years
• Post-PE syndrome: 50% at 2 years (persistent dyspnea, reduced exercise capacity, impaired quality of life without overt CTEPH)
• Residual thrombus: 40-50% at 6 months on imaging; clinical significance unclear

Follow-Up

3-6 months post-PE:

• Clinical assessment (dyspnea, exercise tolerance)
• Echocardiography (if symptoms or intermediate/high-risk PE initially)
• V/Q scan (if echo shows elevated RVSP or symptoms)
• Consider CTEPH referral if persistent symptoms and abnormal V/Q

Annual assessment (if on indefinite anticoagulation):

• Bleeding risk reassessment (HAS-BLED score)
• Recurrence risk assessment
• Renal function (if on DOAC)
• Patient preference for continuing anticoagulation

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CICM Exam Practice

SAQ 1: Massive PE Management

Scenario: A 62-year-old woman presents with sudden-onset dyspnea and chest pain. She is hypotensive (BP 82/50 mmHg), tachycardic (HR 135 bpm), and hypoxemic (SpO2 88% on 15 L non-rebreather mask). CTPA confirms bilateral main pulmonary artery thrombi.

Question: Outline your immediate management of this patient. (10 marks)

Model Answer:

1. Resuscitation and Supportive Care (3 marks)

• Airway/Breathing: High-flow oxygen to maintain SpO2 ≥90%; consider HFNO or mechanical ventilation if refractory hypoxemia (note: positive pressure ventilation may worsen hemodynamics by reducing venous return)
• Circulation:
  • Judicious IV fluid bolus (250-500 mL crystalloid); avoid overload (worsens RV function)
  • "Vasopressor: Norepinephrine infusion (0.05-0.5 mcg/kg/min) to maintain MAP ≥65 mmHg"
  • "Inotrope: Dobutamine (2.5-10 mcg/kg/min) if low cardiac output despite adequate preload"
• Monitoring: Continuous cardiac monitoring, arterial line, central venous access, urinary catheter

2. Anticoagulation (1 mark)

• UFH: 80 units/kg IV bolus, then 18 units/kg/h infusion (target aPTT 60-80 sec)
• Rationale: Immediate anticoagulation; UFH preferred in unstable patients (short half-life, reversible)

3. Reperfusion Therapy (4 marks)

• Systemic thrombolysis (first-line for massive PE):
  • Alteplase 100 mg IV over 2 hours (or 50 mg IV bolus if in extremis)
  • "Assess contraindications: Prior ICH, recent major surgery/trauma, active bleeding"
  • Pause UFH during infusion; resume without bolus once aPTT below 80 sec (typically 3-4 hours post-infusion)
• Alternative reperfusion (if thrombolysis contraindicated or failed):
  • "Catheter-directed thrombolysis: Ultrasound-assisted (EKOS); alteplase 10-24 mg over 6-15 hours"
  • "Surgical embolectomy: Median sternotomy, cardiopulmonary bypass, thrombectomy"
  • "VA-ECMO: Bridge to recovery or definitive therapy"

4. Monitoring and Complications (2 marks)

• Neurological checks every 1 hour for 24 hours (detect intracranial hemorrhage)
• Serial labs: Hemoglobin, platelet count, fibrinogen, aPTT
• Response to thrombolysis: Hemodynamic improvement typically within 1-2 hours; maximal at 12-24 hours
• Bleeding management: Stop thrombolysis, reverse anticoagulation (protamine), tranexamic acid 1 g IV, blood products

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SAQ 2: Risk Stratification and Anticoagulation

Scenario: A 54-year-old man presents with sudden dyspnea and pleuritic chest pain. He has a history of obesity (BMI 38) and recent long-haul flight. Vitals: BP 128/76 mmHg, HR 102 bpm, SpO2 94% on room air. CTPA confirms segmental PE in right lower lobe. Echocardiography shows RV/LV ratio 0.7, normal TAPSE. Troponin I 0.03 ng/mL (normal below 0.04), BNP 85 pg/mL (normal below 100).

Question: a) What is the ESC 2019 risk category for this patient? (2 marks) b) Outline your anticoagulation management, including choice of agent and duration. (8 marks)

Model Answer:

a) Risk Category (2 marks)

• Low-risk PE:
  • Hemodynamically stable (BP 128/76 mmHg)
  • No RV dysfunction (RV/LV ratio 0.7, normal TAPSE)
  • Negative biomarkers (troponin and BNP normal)
  • sPESI = 0 (age below 80, no cancer, no chronic cardiopulmonary disease, HR below 110, SBP ≥100, SpO2 ≥90%)
• 30-day mortality: below 1%

b) Anticoagulation Management (8 marks)

Choice of Agent (4 marks):

• First-line: DOAC (preferred over warfarin):
  • "Apixaban: 10 mg PO BID × 7 days → 5 mg PO BID"
  • "OR Rivaroxaban: 15 mg PO BID × 21 days → 20 mg PO daily"
  • "OR Edoxaban: Requires LMWH/UFH lead-in × ≥5 days → 60 mg PO daily"
  • "OR Dabigatran: Requires LMWH/UFH lead-in × ≥5 days → 150 mg PO BID"
• Advantages: No monitoring, rapid onset, lower ICH risk, non-inferior efficacy
• Check renal function: CrCl (if below 30 mL/min, avoid most DOACs except apixaban at reduced dose if CrCl 15-29)
• Assess bleeding risk: HAS-BLED score

Alternative if DOAC contraindicated (1 mark):

• LMWH (enoxaparin 1 mg/kg SC BID) overlapping with warfarin (target INR 2-3) × ≥5 days

Duration (3 marks):

• Provoked PE: If clear transient risk factor (long-haul flight alone is weak risk; obesity is ongoing risk) → Consider unprovoked
• Recommendation: Minimum 3 months; reassess at 3 months
  • "If provoked (attributing to flight + obesity): 3 months, then stop"
  • "If unprovoked (obesity alone insufficient): Consider 6-12 months or indefinite if low bleeding risk"
• Annual reassessment if continued: Bleeding risk (HAS-BLED), recurrence risk, patient preference

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Viva 1: High-Risk PE – Thrombolysis Decision-Making

Viva Stem:

A 68-year-old woman presents to the emergency department with sudden dyspnea and syncope. She has a history of hypertension and type 2 diabetes. On examination, she is confused, BP 78/45 mmHg, HR 138 bpm, RR 32/min, SpO2 85% on 15 L O2 via non-rebreather mask. She is cold and clammy with poor peripheral perfusion. ECG shows sinus tachycardia and right heart strain (T wave inversion V1-V4, S1Q3T3). Bedside echocardiography demonstrates severe RV dilation (RV/LV ratio 1.3), hypokinesis of RV free wall, and tricuspid regurgitation. CTPA confirms bilateral main and lobar pulmonary artery thrombi.

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Question 1: How would you classify the severity of this patient's pulmonary embolism? (Examiner expects: risk stratification)

Model Answer:

• This is high-risk (massive) PE based on ESC 2019 criteria
• Hemodynamic instability:
  • Persistent hypotension (SBP 78 mmHg)
  • Signs of shock (confusion, cold/clammy, poor perfusion)
  • Evidence of end-organ hypoperfusion
• Supporting features:
  • Severe RV dysfunction on echo (RV/LV ratio 1.3; normal below 0.6)
  • ECG changes consistent with RV strain
  • Bilateral main/lobar PE on CTPA (large thrombus burden)
• 30-day mortality: 15-30% (up to 58% without reperfusion therapy)

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Question 2: What is your immediate management? (Examiner expects: resuscitation priorities)

Model Answer:

Resuscitation:

• Airway/Breathing: High-flow oxygen; prepare for intubation (preoxygenate carefully; intubation can precipitate arrest)
• Circulation:
  • Small fluid bolus (250 mL crystalloid); avoid overload
  • "Vasopressor: Norepinephrine infusion to maintain MAP ≥65 mmHg"
  • "Inotrope: Consider dobutamine if low cardiac output"

Anticoagulation:

• UFH: 80 units/kg IV bolus, then 18 units/kg/h infusion (pause during thrombolysis)

Definitive Therapy:

• Systemic thrombolysis is indicated (high-risk PE)

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Question 3: The patient had a fall 10 days ago with a head CT showing small subdural hematoma (SDH) that was managed conservatively. How does this change your management? (Examiner probes: relative contraindication, risk-benefit)

Model Answer:

• Recent head trauma with SDH is a relative contraindication to thrombolysis
• Risk-benefit analysis:
  • "Risk of thrombolysis: Intracranial hemorrhage (ICH) 1-3% in general population; higher with pre-existing SDH (risk ~5-10%)"
  • "Risk of no thrombolysis: 30-58% mortality from massive PE"
• Decision:
  • Multidisciplinary discussion (ICU, neurosurgery, interventional radiology)
  • "Consider alternatives:"
    1. Catheter-directed thrombolysis: Lower thrombolytic dose (10-24 mg alteplase over 6-15 hours vs 100 mg systemic); reduced ICH risk (~0-1%)
    2. Surgical pulmonary embolectomy: If surgical team available and patient stable enough for transfer
    3. VA-ECMO: Bridge to recovery or definitive therapy
  • "If no alternative available and patient deteriorating: May still proceed with systemic thrombolysis (life-threatening situation; mortality without treatment greater than 50%)"

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Question 4: You proceed with catheter-directed thrombolysis. Six hours later, the patient develops massive hemoptysis. How would you manage this? (Examiner expects: bleeding complication management)

Model Answer:

Immediate actions:

1. Stop thrombolytic infusion immediately
2. Reverse anticoagulation:
   • UFH: Protamine sulfate 1 mg per 100 units of heparin given in last 2-3 hours (max 50 mg over 10 min)
   • Check aPTT to confirm reversal
3. Antifibrinolytic therapy:
   • Tranexamic acid 1 g IV over 10 min (inhibits plasminogen activation)
4. Blood products:
   • Cryoprecipitate (10 units) or fibrinogen concentrate (target fibrinogen greater than 150 mg/dL)
   • Packed RBCs: Maintain Hb greater than 70 g/L (higher target if ongoing bleeding or hemodynamic instability)
   • Platelets: If below 50,000/mm³ or platelet dysfunction suspected
   • Fresh frozen plasma (FFP): If INR elevated or coagulopathy

Airway management:

• Position patient with bleeding side down (if lateralizable) to protect contralateral lung
• Intubation: May be required for airway protection (large-bore endotracheal tube ≥8.0 mm to allow bronchoscopy)
• Selective intubation: Consider double-lumen tube or bronchial blocker to isolate bleeding lung

Definitive hemostasis:

• Bronchoscopy: Identify bleeding source; consider bronchial artery embolization (BAE) if accessible
• CT angiography chest: Identify bleeding vessel if bronchoscopy unsuccessful
• Interventional radiology: Bronchial artery embolization

Ongoing monitoring:

• Serial hemoglobin, coagulation studies (PT/INR, aPTT, fibrinogen), platelet count
• Monitor for hemodynamic deterioration

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Examiner's Summary Points:

• High-risk PE requires urgent reperfusion (thrombolysis, CDT, embolectomy, ECMO)
• Relative contraindications require risk-benefit analysis and consideration of alternatives
• Catheter-directed therapy offers lower bleeding risk than systemic thrombolysis
• Bleeding complications: Stop thrombolytic, reverse anticoagulation, antifibrinolytics, blood products, definitive hemostasis

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Viva 2: Intermediate-Risk PE – To Thrombolyse or Not?

Viva Stem:

A 72-year-old man presents with sudden dyspnea. He has a history of COPD and atrial fibrillation (on apixaban). Vitals: BP 118/72 mmHg, HR 115 bpm (AF), RR 28/min, SpO2 89% on room air (baseline 93%). CTPA confirms bilateral lobar PE. Echocardiography shows RV/LV ratio 1.1, reduced TAPSE (12 mm), moderate tricuspid regurgitation. Troponin I 0.18 ng/mL (normal below 0.04), NT-proBNP 1,850 pg/mL.

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Question 1: How would you risk-stratify this patient, and what is the anticipated mortality? (Examiner expects: ESC 2019 classification)

Model Answer:

• Intermediate-high risk PE:
  • Hemodynamically stable (SBP 118 mmHg, no shock)
  • "RV dysfunction present:"
    • Echo: RV/LV ratio 1.1 (normal below 0.6; abnormal greater than 0.9)
    • Reduced TAPSE (12 mm; normal greater than 16 mm)
  • "Positive biomarkers:"
    • Elevated troponin I (0.18 ng/mL; ULN 0.04)
    • Elevated NT-proBNP (1,850 pg/mL; abnormal greater than 500)
• 30-day mortality: 3-15% (vs below 1% for low-risk)
• Risk of hemodynamic decompensation: 5-10%

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Question 2: Would you give systemic thrombolysis to this patient? (Examiner expects: evidence-based discussion of PEITHO trial)

Model Answer:

No, systemic thrombolysis is NOT routinely recommended for intermediate-risk PE (ESC 2019 Class III recommendation).

Evidence (PEITHO trial, 2014):

• 1,005 patients with intermediate-risk PE
• Tenecteplase vs placebo (both groups received heparin)
• Results:
  • "Benefit: Reduced hemodynamic decompensation (2.6% vs 5.6%; p=0.02)"
  • "Harm: Increased major bleeding (6.3% vs 1.2%; pbelow 0.001) and intracranial hemorrhage (2.0% vs 0.2%; p=0.003)"
  • No mortality benefit (1.2% vs 1.8%; p=NS)
• Age greater than 75 years: Subgroup with particularly high bleeding risk (ICH 4.3% vs 0%)

Conclusion: Risk of bleeding outweighs benefit of preventing decompensation in stable intermediate-risk PE.

Current recommendation:

• Anticoagulation alone (therapeutic dose)
• Close monitoring (ICU or step-down unit)
• Rescue thrombolysis if clinical deterioration (worsening hypotension, hypoxemia, shock)

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Question 3: The patient is started on therapeutic anticoagulation and admitted to the ICU for monitoring. Six hours later, his BP drops to 88/50 mmHg, HR increases to 135 bpm, and SpO2 falls to 84% on 15 L O2. What would you do now? (Examiner probes: rescue thrombolysis)

Model Answer:

• Clinical deterioration: Transition from intermediate-high risk to high-risk PE (hemodynamic instability)
• Reassess:
  • Rule out alternative causes (e.g., bleeding, arrhythmia, pneumothorax, cardiac tamponade)
  • Repeat echo (assess RV function progression)

Management:

1. Resuscitation:
   • Oxygen/ventilatory support (HFNO or intubation)
   • Vasopressor (norepinephrine) to maintain MAP ≥65 mmHg
2. Rescue thrombolysis is now indicated (high-risk PE):
   • Alteplase 100 mg IV over 2 hours
   • Assess contraindications (this patient: age 72, on apixaban)
3. Alternative if thrombolysis contraindicated:
   • Catheter-directed thrombolysis (ultrasound-assisted)
   • Surgical embolectomy
   • VA-ECMO

Apixaban reversal (if thrombolysis planned):

• Andexanet alfa (Andexxa): 400-800 mg IV bolus, then infusion
• Alternative: 4-factor prothrombin complex concentrate (PCC): 50 units/kg IV
• Check anti-Xa level after reversal

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Question 4: After thrombolysis, the patient's BP improves to 105/60 mmHg, HR 102 bpm, SpO2 94% on 6 L O2. When would you restart anticoagulation, and what agent would you use? (Examiner expects: timing and choice of anticoagulant)

Model Answer:

Timing:

• Restart anticoagulation 12-24 hours after completion of thrombolysis (once hemodynamically stable and no active bleeding)
• If UFH was used during thrombolysis, resume without bolus once aPTT below 80 sec (typically 3-4 hours post-infusion)

Choice of agent:

• Avoid immediate DOAC (patient was on apixaban prior; may have been reversed)
• Bridging strategy:
  1. UFH infusion (18 units/kg/h; target aPTT 60-80 sec) × 24-48 hours
  2. Transition to DOAC once stable:
     • Apixaban: 10 mg PO BID × 7 days → 5 mg PO BID
     • (Original agent; effective and well-tolerated)
• Alternative: LMWH (enoxaparin 1 mg/kg BID) × 5-7 days → transition to apixaban

Duration:

• Minimum 3 months; reassess at 3 months
• If unprovoked (likely in this case): Consider 6-12 months or indefinite if low bleeding risk (HAS-BLED score)
• CTEPH screening: Echo and/or V/Q scan at 3-6 months if persistent dyspnea

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Examiner's Summary Points:

• Intermediate-risk PE: Anticoagulation + close monitoring (NOT routine thrombolysis)
• PEITHO trial: Thrombolysis reduces decompensation but increases bleeding
• Rescue thrombolysis indicated if deterioration to high-risk PE
• Age greater than 75 years: Very high ICH risk with thrombolysis (4.3% in PEITHO)

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Summary

Pulmonary embolism is a common and potentially fatal cardiovascular emergency requiring rapid risk stratification and tailored management. High-risk (massive) PE with hemodynamic instability mandates urgent reperfusion therapy with systemic thrombolysis (alteplase 100 mg over 2 hours), catheter-directed therapy, surgical embolectomy, or VA-ECMO. Intermediate-high risk PE (stable with RV dysfunction and elevated biomarkers) should receive anticoagulation and close monitoring, with rescue thrombolysis reserved for clinical deterioration (PEITHO trial demonstrated no mortality benefit and increased bleeding with routine thrombolysis). Low-risk PE is managed with anticoagulation alone, with DOACs (apixaban, rivaroxaban) preferred over warfarin. Age-adjusted D-dimer cutoffs improve diagnostic specificity, and CTPA remains the gold-standard imaging modality. Long-term complications include CTEPH (2-4% of survivors) and post-PE syndrome (50% at 2 years), mandating follow-up echocardiography and V/Q scanning at 3-6 months in symptomatic patients.