Diagnosis

Pulmonary embolism

Etiology

Cause [fqu]

• A complication of thrombosis in the deep venous system:

  • DVT from the lower extremities

  • Rarely: pelvic, renal, upper extremity veins or atrium

• Other rare causes: Air, fat, or tumor cells embolism

Pathophysiology [fqu]

1. Formation of thrombi (Virchow triad):

   • Endothelial injury

   • Stasis/turbulence of blood flow

   • Hypercoagulability

2. Accretion of platelets and fibrin cause formation of thrombus

3. Total occlusion of the vein (Deep Venous Thrombosis)

4. Break off and embolize

5. Large saddle embolus can obstruct the main pulmonary artery and may cause:

   • Respiratory failure due to impaired gas exchange:

     • Alveolar dead space

     • Ventilation-perfusion mismatch

     • Pulmonary infarction (intra-alveolar hemorrhage)

   • Hemodynamic compromise

     • Increased pulmonary vascular resistance

     • Increased right ventricular afterload

     • Reduced cardiac output

6. Classification of pulmonary embolism:

   • Hemodynamically stable PE: mildly symptomatic, or asymptomatic

   • Hemodynamically unstable PE: risk of right ventricular failure and shock

     • Systolic blood pressure <90 mm Hg

     • Drop in systolic blood pressure of ≥40 mm Hg from baseline

     • Hypotension that requires vasopressors or inotropes

Risk factors [fqu][hpm]

• Hereditary risk factors: Antithrombin III deficiency, Protein C deficiency, Protein S deficiency, Factor V Leiden, Plasminogen abnormality, Plasminogen activator abnormality, Fibrinogen abnormality, Resistance to activated protein C

• Acquired risk factors: Old age, cancer, immobilization (paresis, heart failure, respiratory failure, trauma, fracture), smoking, recent surgery, pregnancy, hormone replacement therapy, oral contraceptive therapy, fibrillation/flutter, central venous lines, chemotherapy, infection, obesity

• High-risk Pulmonary Embolism: Shock, hypotension, CT/echocardiography (RV dilatation, hypokinesis or pressure overload), elevated BNP/proBNP, elevated cardiac troponin, right heart catheterization (Elevated right heart pressure)

Complications [fqu]

• Recurrent thromboembolism

• Chronic thromboembolic pulmonary hypertension

• Right heart failure

• Cardiogenic shock

Epidemiology

Incidence per 100.000 [dfv][too][pyr][fqu][5rs][hpm][pvf][so1][udu][bac][4id][nyf][cad][q9g][bzf][sis][8em]

Approach

• Blood test: [hpm][fqu]

  Troponin, BNP, D-dimer (high negative predictive value in patients with a low or moderate clinical probability)

• Blood gas

• ECG

• Echocardiography: right ventricule overload

• Chest x-ray

• CT angiography

• V/Q scanning

• Venography

• Duplex ultrasonography: Compression of the deep veins

Flowchart for diagnosis [hpm]

1. Suspected non-high-risk Pulmonary Embolism -> Clinical score (Wells/Geneva)

   • Low/intermediate clinical probability -> D-dimer:

     • Negative D-dimer -> No treatment

     • Positive D-dimer -> CT

   • High clinical probability -> CT:

     • No PE -> No treatment (investigate further)

2. Suspected high-risk Pulmonary Embolism: Right Ventricule failure -> shock

   • Stable patient -> CT

   • Unstable patient -> Echocardiography

Geneva score [d7k]

1. Predisposing factors

   • +1 Age > 65years

   • +3 Previous DVT or PE

   • +2 Surgery or fracture within 1 month

   • +2 Active malignancy

2. Symptoms

   • +3 Unilateral lower limb pain

   • +2 Hemoptysis

3. Clinical signs

   • +3 heart rate 75-94 beats/min

   • +5 heart rate ≥95 beats/min

   • +4 Pain on palpation and unilateral edema on lower limb

4. Clinical probability:

   • 0-3 Low (~10%)

   • 4-10 Intermediate (~30%)

   • ≥11 High (~65%)

Wells score [s6c]

1. Predisposing factors

   • +1.5 Previous DVT or PE

   • +1.5 Recent surgery or immobilization

   • +1 Cancer

2. Symptoms

   • +1 Hemoptysis

3. Clinical signs

   • +1.5 heart rate >100 beats/min

   • +3 Clinical signs of DVT

   • +3 Alternative diagnosis less likely than PE

4. Clinical probability:

   • 0-1 Low (10%)

   • 2-6 Intermediate (~30%)

   • ≥7 High (~65%)

Treatment

Hemodynamically stable PE [hpm]

• Enoxaparin 1.0 mg/kg Every 12 h or 1.5 mg/kga Once daily

• Warfarin: INR of 2.5 (range 2.0–3.0) duration of 3–6 months

Hemodynamically unstable PE [hpm]

1. Oxygen:

   • Increase supply: nasal/mechanical ventilation without PEEP to maximize preload

   • Decrease consumption (reduce fever and agitation)

2. Modest fluid resucitation

3. Inotropic drugs (Isoproterenol, Norepinephrine, Dobutamine, Dopamine)

4. Vasodilators administered by inhalation (nitric oxide) decrease pulmonary vascular resistance

5. Anticoagulation:

   • Enoxaparin 1.0 mg/kg Every 12 h or 1.5 mg/kga Once daily

6. Thrombolysis: contraindicated of stroke/brain hemorrhage, brain cancer, major trauma/surgery. Relative contraindication: pregnancy, liver failure, endocarditis, ulcer, traumatic resuscitation

   • Recombinant tissue plasminogen activator (rtPA) 100 mg over 2 h or 0.6 mg/kg over 15 min (maximum dose 50 mg)

   • Streptokinase 250 000 IU as a loading dose over 30 min, followed by 100 000 IU/h over 12– 24 h. Accelerated regimen: 1.5 million IU over 2 h

   • Urokinase 4400 IU/kg as a loading dose over 10 min, followed by 4400 IU/kg/h over 12– 24 h. Accelerated regimen: 3 million IU over 2 h

7. Embolectomy (endovascular/surgical):

   • Alternative to thrombolysis when there are absolute contraindications

   • Adjunctive therapy when thrombolysis has failed to improve hemodynamics

8. Vena cava filter: Retrievable filters may be considered in selected patients with recurrent venoius thromboembolism (DVT or PE) despite anticoagulation or in patients with absolute contraindication to anticoagulants [fqu]

Differential diagnoses

Acute respiratory distress syndrome, Allergic alveolitis, Angina pectoris, Anxiety, Aortic stenosis, Arrhythmia, Atrial fibrillation, Cardiac tamponade, Cardiomyopathy, COPD, Cor pulmonale, Emphysema, Fat embolism syndrome, Heart failure, Hyperventilation, Mediastinitis, Mitral stenosis, Myocardial infarction, Pericarditis, Pleuritis, Pneumonia, Pneumonitis, Pneumothorax, Pulmonary edema, Pulmonary hypertension, Shock, Sickle cell disease, Superior vena cava syndrome, Syncope, Vasovagal syncope