Pulmonary Embolism Diagnosis, Treatment, and Prevention

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Pulmonary EmbolismDiagnosis, Treatment, and
Prevention

• Philip Keith
• March 26, 2008

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Pulmonary Embolism

• Thrombosis that originates in the venous system
  and embolizes to the pulmonary arterial
  circulation
• DVT in veins of leg above the knee (gt90)
• DVT elsewhere (pelvic, arm, calf veins, etc.)
• Cardiac thrombi

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How Common?

• 650,000 cases in the US each year
• 150,000 200,000 US deaths each year
• Most common preventable cause of hospital death
• 3rd most common acute cardiovascular emergency
  (MI and stroke)

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Risk Factors (for DVT)

• Virchows Triad
• Alterations in blood flow (stasis) best rest,
  inactivity/immobilization, CHF, paralysis
• Injury to endothelium trauma, surgery
• Thrombophilia Factor V Leiden, Protein C or S
  deficiency, etc.
• Age gt50
• History of varicose veins
• History of MI
• History of malignancy
• History of atrial fibrillation
• History of ischemic stroke
• History of diabetes mellitus
• Previous VTE, obesity, pregnancy

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Clinical Presentation

• Asymptomatic
• Sudden onset of unexplained dyspnea
• Pleuritic chest pain
• Tachypnea
• Tachycardia
• Anxiety/agitation, cough, hemoptysis, syncope,
  fever, cyanosis, isolated crackles, pleural
  friction rub, loud P2, right-sided S3, pulmonary
  insufficiency murmur, elevated JVP, right
  ventricular heave, acute worsening of heart
  failure or lung disease

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Broad Differential

• Pneumothorax
• Myocardial ischemia
• Pericarditis
• Asthma
• Pneumonia
• MI with cardiogenic shock
• Cardiac tamponade
• Aortic dissection
• etc, etc, etc

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Nonspecific Workup

• Chest X-ray abnormal in 88 of acute PE
• Atelectasis (60-70) most common finding in PE
  without infarction
• Classic findings
• Westermark sign (increased lucency in area of
  embolus)
• Hampton Hump (wedge-shaped pleural-based
  infiltrate)
• Abrupt cutoff of vessel
• Pleural effusion
• EKG
• Most common sinus tachycardia /- nonspecific
  ST-segment and T-wave changes
• Classic S1-Q3-T3 pattern
• Other signs of right heart strain (ie, new RBBB
  and ST changes in V1,2
• ABG
• Normal does NOT rule out PE
• Classic findings
• Hypoxia, hypocapnia, respiratory alkalosis,
  increased A-a gradient

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Westermark Sign
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Hampton Hump
Occurs 12 to 36 hours after symptoms
begin usually indicates pulmonary infarction
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EKG Findings
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Evaluation and Diagnosis

• Evaluation and imaging is dependent upon
  estimated pretest probability (Modified Wells
  Criteria)
• Pretest probability
• Low (lt2 points)
• Intermediate (2-6 points)
• High (gt6 points)

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REFER TO ALGORITHM
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D-dimer in evaluation of PE

• High sensitivity but poor specificity
• Negative ELISA has gt95 negative predictive value
  and can be used to r/o PE in low risk patients
  (less than 2 points)

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Helical CT

• Sensitivity 85 (more sensitive for proximal
  emboli)
• Specificity 95
• Values vary widely in literature

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Bilateral PE
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V/Q Scan

• Identifies mismatches between areas that are
  ventilated but not perfused
• Best initial test in patients with clear CXR
• Scan can be interpreted as High, Intermediate, or
  Low probability of PE, or normal
• Normal rules out PE
• High-probability scan is diagnostic of PE if the
  clinical suspicion is also high
• Low-probability scan rules out PE only in a pt
  with low pretest clinical probability (because PE
  is found in roughly 15 of pts with
  low-probability scans)
• Intermediate-probability scan requires further
  evaluation (16-66 chance of PE depending on
  pretest probability)

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V/Q Scan
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Duplex US with compression of the lower
extremities

• Non-invasive test that accurately detects
  proximal DVT in LE (70-80 of pts with PE have
  concomitant proximal DVT)
• Often used in workup of PE before going to more
  invasive procedures
• SEE ALGORITHM

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Pulmonary Angiography

• Gold Standard
• Invasive study
• 5 morbidity
• lt 0.5 mortality
• Indicated if the diagnosis remains uncertain
  after noninvasive testing

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PE on pulmonary angiogram
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Treatment of PE

• Acute anticoagulation to therapeutic levels
• IV UFH 80 U/kg bolus, then 18 U/kg/hr to goal
  PTT of 46-70 seconds OR
• LMWH ie) lovenox 1 mg/kg SUBQ BID then start
  warfarin (when PTT is therapeutic on UFH or on
  day 1 of LMWH), overlap x 5 days, titrate to INR
  2.0 to 3.0
• Thrombolysis for massive PE causing hemodynamic
  compromise
• IVC Filter if anticoagulation is contraindicated
  (ie, active GI bleed, intracranial neoplasm, know
  bleeding diathesis), if thrombus formed despite
  adequate anticoagulation, or with a large burden
  of thrombosis in the LE that could be fatal if
  embolized

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Treatment of PE

• Long-term anticoagulation
• 1st event with reversible RF 3-6 mo warfarin
• Idiopathic PE/DVT gt or 6 mo warfarin
• 2nd event, cancer, non-modifiable RF 12 mo to
  lifelong warfarin
• LMWH has been shown to be superior to warfarin in
  long term treatment in pts with cancer

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DVT/PE Prophylaxis

• Moderate to High Risk Patients (gt2 RF)
• Lovenox 30 mg SUBQ q 12 hours OR
• Lovenox 40 mg SUBQ daily
• SCD at all times except when ambulating
• Low to Moderate Risk Patients ( 1 RF)
• Lovenox 40 mg SUBQ daily OR
• SCD at all times except when ambulating
• No Risk Factors
• Ambulate in hallways or room QID
• TED hose or SCD