Pulmonary Embolism

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Contents 1 Etiology 2 Epidemiology 3 Clinical-manifestations 4 Laboratory 5 Diagnostic-procedures 6 Radiology 7 Complications 8 Differential-diagnosis 9 Management 10 More General Terms 11 Additional Terms 12 References

Etiology

• source

• majority of clinically significant pulmonary emboli arise from deep venous thromboses ( DVT) in the iliac artery - femoral artery system
• post surgically, the pelvic venous complex is a source of pulmonary emboli

• predisposing factors

• venous disease of the lower extremities

• deep vein thrombosis
• varicosities

• carcinoma
• heart failure
• recent pelvic or lower abdominal surgery
• prolonged immobilization, includes sitting [24]
• pregnancy
• estrogen therapy
• fracture of hip or leg
• chronic lung disease
• hypercoagulable states
• atrial fibrillation
• trauma
• hospitalization for autoimmune disease (HR=10) [25]

Epidemiology

• cause of death in 5-15% of hospitalized patients in US
• detected in 25-30% of routine autopsies
• prevalence of 1% in hospitalized patients

Clinical-manifestations

• pulmonary embolism is generally asymptomatic
• dyspnea
• pleuritic chest pain
• apprehension
• cough
• lower extremity edema, leg pain
• tachypnea
• tachycardia
• hemoptysis
• accentuation of the pulmonic component of the 2nd heart sound
• wheezing
• crackles
• fever
• cyanosis
• S4 heart sound
• syncope [8]
• hypotension [26]

Laboratory

• arterial blood gas ( ABG)*

• hypoxia
• increased P(A-a)O2 gradient correlates with severity
• 20% of patients with PE show normal P(A-a)O2 gradient
• pCO2 is generally diminished

• pulse oximetry*: low SaO2 (hyoxia)
• D-dimer may be elevated in pulmonary embolism

• increased D-dimers have no positive predictive value
• normal D-dimer excludes PE in < 30% of suspected cases
• negative D-dimer & low clinical probability excludes pulmonary embolism [10,14,17]

• serum LDH: increased
• serum bilirubin: increased (normal with MI)
• serum AST may be normal (elevated with MI)
• complete blood count ( CBC) leukocytosis
• serum troponin I:

• increase suggests right ventricular strain
  

• * a normal pO2 or SaO2 does not rule out PE

Diagnostic-procedures

• electrocardiogram
• sinus tachycardia
• infrequent changes: (15%)

• S in lead I
• Q in lead III
• T wave abnormality in lead III

• right axis deviation
• incomplete right bundle branch block
• inverted T waves in right precordial leads (40%)

Radiology

• chest X-ray: PA & lateral

• normal in 30% of patients
• Hampton's hump on lateral view
• elevated hemidiaphragm may be seen (40%)
• enlarged pulmonary artery (20%)

• ventilation-perfusion scan ( VQ scan) showing VQ mismatch [23]
• evaluation for DVT by Doppler ultrasonography
• pulmonary angiography [15]
• CT angiography (spiral CT) detects emboli [12]

• detects emboli in main, lobar or segmental arteries but not subsegmental arteries
• 2nd generation helical CT may be better [14]
• indicated in patients with abnormal D-dimer &/or high clinical suspicion [17]
• pulmonary CT angiography 83% sensitivity [18],
• may preclude need for ultrasound of lower extremity to rule out DVT [20]
• more than twice as likely to find an incidental nodule or adenopathy as it is to find PE [21]
• reserve for patients with indeterminate findings on ventilation-perfusion scan ( VQ scan) [21]

Complications

• pulmonary infarction (< 10%)
• recurrent pulmonary embolism (8%)
• secondary pulmonary hypertension (0.5-4%) occurs within 2 years [13]
• acute cor pulmonale occurs when > 65% of vasculature is obstructed by pulmonary embolism
• occult malignancy (8% over two years)
• mortality is 7% when diagnosed at presentation
• heparin-induced thrombocytopenia
• risk factors [25]

• oxygen saturation <90% on room air
• systolic blood pressure <100 mm Hg
• chest pain requiring opioids
• active bleeding, or were at high risk for hemorrhage

• recent stroke
• gastrointestinal bleeding
• platelet count >75,000/ mm3

• older age
• malignant neoplasm

Differential-diagnosis

• asthma
• bronchopneumonia
• pleurisy
• pericarditis
• pneumothorax
• myocardial infarction
• acute pancreatitis
• perforated peptic ulcer

Management

• supportive therapy
• anticoagulation

• heparin IV to maintain aPTT 60-90 sec, or
• LMW heparin for 5-10 days [5]

• enoxaparin

• 1.5 mg/kg QD or
• 1 mg/kg BID)

• dalteparin 200 units/kg SQ QD
• tinzaparin 175 units/kg SQ QD
• fondaparinux

• < 50 kg (< 110 lbs) 5 mg SQ QD
• 50-100 kg (110-220 lbs) 7.5 mg SQ QD
• > 100 kg (> 220 lbs) 10 mg SQ QD [5]

• warfarin (begin concurrently with heparin or LMW heparin)

• bolus, 10 mg QD for 1-2 days
• begin at 2.5 mg QD
• adjust dose to achieve INR of 2.0-3.0
• maintain INR 2.0-3.0 for at least 3 months [4,19]

• initiation of anticoagulation with rivaroxaban may be alternative to LMW heparin followed by warfarin [27]
• empiric anticoagulation prior to confirmation if high- probability of PE [4]
• duration of anticoagulation

• 1st episode of thromboembolism with reversible risk factors: 3 months
• 1st episode of idiopathic thromboembolism: 6-12 months with consideration for life-long therapy
• recurrent episodes of thromboembolism or 1st episode with hypercoagulable state: 12 months to life-long therapy [4]

• inferior vena cava interruption, i.e. Greenfield filter should be considered in the following settings:

• anticoagulation is contraindicated

• unless contraindicated, heparin therapy should be continued to prevent extension of a pre-existing clot

• documented recurrent thromboembolic events in patients who are adequately anticoagulated
• massive pulmonary emboli with hemodynamic compromise, especially if the is evidence of residual thrombus in a lower extremity
• patients with compromised cardiac or pulmonary function who might not survive a recurrent event
• patients undergoing pulmonary embolectomy
• patients with paradoxic emboli via a patent foramen ovale
• septic pulmonary emboli from lower extremities or pelvic veins

• systemic thrombolytic therapy

• indications:

• massive pulmonary emboli
• hemodynamically unstable
• low risk of bleeding

• thrombolytic agents

• streptokinase
• urokinase
• tPA

• heparin therapy is necessary after thrombolytic therapy

• pulmonary embolectomy should be considered only in:

• patients with angiographically-proven pulmonary emboli
• patients who remain in shock despite thrombolytic therapy & supportive care, or
• patients in whom thrombolytic therapy is contraindicated

• graduated compression stocking to reduce risk of post-thrombotic syndrome [4]
• routine screening for potentially treatable carcinomas

• breast examination & mammography
• Pap Smear
• sigmoidoscopy
• prostate-specific antigen (PSA)
• chest X-ray

• low risk patients may be treated as outpatient [25]

More General Terms

• pulmonary vascular disease
• venous thromboembolism (VTE)
• embolism

Additional Terms

• clinical decision rules for pulmonary embolism
• deep vein thrombosis (DVT)
• fibrinolytic agent (thrombolytic agent)
• Greenfield filter; umbrella; inferior vena cava filter
• hypercoagulability
• Prospective Investigation Of Pulmonary Embolism Diagnosis (PIOPED) study
• thrombolytic therapy

References

1. Manual of Medical Therapeutics, 28th edition, Ewald & McKenzie (eds) Little, Brown & Co, 1995, pg 247-49
2. DeGowin & DeGowin's Diagnostic Examination, 6th edition, RL DeGowin (ed), McGraw Hill, NY 1994, pg 242-243
3. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 775-78
4. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, American College of Physicians, Philadelphia 1998, 2006
5. Journal Watch 21(6):48, 2001 Merli G et al Subcutaneous enoxaparin once or twice daily compared with intravenous unfractionated heparin for treatment of venous thromboembolic disease. Ann Intern Med 134:191, 2001 PMID: [1]
6. Goldhaber SZ & Mmorpurgo M Diagnosis, treatment, and prevention of pulmonary embolism. Report of the WHO/International Society and Federation of Cardiology Task Force. JAMA 268:1727, 1992 PMID: [2]
7. Kinasewitz GT Thrombophlebitis and pulmonary embolism in the elderly patient. Clin Chest Med 14:523, 1993 PMID: [3]
8. Wilk JS et al Unexplained syncope: when to suspect pulmonary thromboembolism. Geriatrics 50:46, 1995 PMID: [4]
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    - Prescriber's Letter 18(4): 2011 COMMENTARY: Duration of Anticoagulation After Venous Thromboembolism GUIDELINES: Antithrombotic Therapy for Venous Thromboembolic Disease (June 2008) GUIDELINES: Management of Massive and Submassive Pulmonary Embolism, Iliofemoral Deep Vein Thrombosis, and Chronic Thromboembolic Pulmonary Hypertension (March 2011) Detail-Document#: [27] (subscription needed) [28]
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pulmonary embolism (PE)