SIGNS AND SYMPTOMS 
- Variability in signs and symptoms make diagnosis difficult
- Most common:
- General:
- Pulmonary:
- Cardiovascular:
- Extremities:
- Abdominal pain
- Symptoms similar in elderly but typically more subtle if age < 40 yr
ESSENTIAL WORKUP
- Routine labs are nonspecific.
- CXR:
- Used to rule out other causes
- Most common findings with PE:
- Other findings with PE:
- Pleural effusions
- Pleural-based opacities (Hampton hump)
- Elevated hemidiaphragm
- Local oligemia (Westermark sign)
- ECG:
- To rule out cardiac etiology
- Usually normal in PE
- Other findings include:
- Modified Wells criteria:
- Popular decision rule that can assist with risk stratification in combination with D-dimer
- Each criterion is given numeric value and if total value < 4, along with negative D-dimer, risk of PE is < 2%:
- Clinical signs/symptoms of DVT: 3 pts
- PE is no. 1 diagnosis: 3 pts
- Heart rate > 100 bpm: 1.5 pts
- Surgery or immobilization for 3 days within last 4 wk: 1.5 pts
- Previous PE or DVT: 1.5 pts
- Hemoptysis: 1 pt
- Malignancy with treatment within last 6 mo: 1 pt
- Pulmonary Embolism Rule-out Criteria (PERC)
- Useful in low prevalence setting (ED) in combination with low clinical suspicion.
- Age < 50 yr
- Heart rate < 100 bpm
- O2 saturation ≥95%
- No hemoptysis
- No estrogen use
- No prior DVT or PE
- No unilateral leg swelling
- No surgery or trauma requiring hospitalization within the past 4 wk
- < 1% risk for PE/DVT in 45 days if PERC score 0
DIAGNOSIS TESTS & INTERPRETATION
Lab
- Arterial blood gas:
- Can show hypoxemia, hypocapnia, respiratory alkalosis, or increased alveolar–arterial (A–a) gradient
- PE still possible with normal A–a gradient
- Does not aid in diagnosis of PE
- CBC:
- Anemia may be contributing factor to dyspnea.
- D-dimer enzyme-linked immunosorbent assay:
- D-dimers are detectable at levels > 500 ng/mL in nearly all patients with PE.
- High sensitivity (close to 100%) with low specificity for PE
- Almost always elevated in patients with malignancy or surgery within the last 3 mo
- Multiple studies confirm that negative enzyme-linked immunosorbent assay D-dimer in combination with low clinical suspicion effectively rules out PE.
Imaging
- Spiral chest CT with IV contrast:
- Has ability to also detect alternative pulmonary abnormalities
- Accurate for identifying PE in proximal pulmonary tree:
- In patients with high pretest probability, positive predictive value of 96%
- In patients with low pretest probability, negative predictive value of 96%
- Ventilation–perfusion scan (V/Q):
- Results reported in probabilities and correlated to clinical suspicion
- Probability of PE with V/Q results:
- Normal or near normal V/Q scan: 4% probability for PE
- Low-probability V/Q scan with low clinical suspicion: 4% probability for PE
- Low-probability V/Q scan with high clinical suspicion: 16–40% probability for PE
- Intermediate V/Q scan: 16–66% probability for PE
- High-probability V/Q scan with low clinical suspicion: 56% probability for PE
- High-probability V/Q scan with high clinical suspicion: 96% probability for PE
- Lower-extremity duplex US:
- Used in patients who would otherwise require pulmonary angiogram
- Presence of DVT requires same anticoagulation as PE.
- Negative lower-extremity duplex does not rule out PE.
- Echocardiogram:
- Used to assess for right heart strain or patent foramen ovale when thrombolysis is a possibility
Diagnostic Procedures/Surgery
Pulmonary angiogram:
- Gold standard for diagnosis
- Used when diagnosis not confirmed or excluded
- Higher complication rate than other modalities
DIFFERENTIAL DIAGNOSIS
[Outline]
PRE-HOSPITAL
- Initial supplemental oxygen
- Establish IV access
- Cardiac monitor
INITIAL STABILIZATION/THERAPY
- Airway, breathing, and circulation
- Provide supplemental oxygen to maintain adequate oxygen saturation.
- Intubate if unable to provide adequate oxygenation.
- Administer IV fluids carefully for hypotensive patients:
- IV vasopressor therapy is indicated if hypotension does not resolve with IV fluids.
ED TREATMENT/PROCEDURES
- Anticoagulation:
- Prevents additional thrombus from forming
- Stabilizes existent clot to prevent migration
- Risk of minor/major bleeding with therapy
- Unfractionated heparin:
- Dose titration fraught with difficulty leading to inadequate therapy
- Goal to maintain partial thromboplastin time test between 1.5 and 2.5 times the control value (60–80 sec)
- Low-molecular-weight heparin:
- At least as effective as unfractionated heparin in multiple prospective randomized trials
- Therapeutic goal automatic with weight-based dosing
- Easier administration and monitoring than heparin with some cost benefit
- Warfarin:
- Oral therapy for long-term anticoagulation
- Goal is international normalized ratio (INR) of 2–3
- Rivaroxaban:
- Oral factor 10a inhibitor
- Recently approved for treatment of PE
- Does not require lab monitoring
- Not recommended in renal/hepatic insufficiency or pregnancy
- No specific antidote but has short half-life in case of bleeding
- Thrombolysis:
- Initiate in hemodynamically unstable patients with confirmed PE.
- Consider in stable patients with PE and severe hypoxemia, massive PE, or right ventricular dysfunction.
- Inferior vena cava filter:
- Indicated in patients who have contraindications to anticoagulation or have been therapeutic on anticoagulation but failed prevention of PE
- Surgical or catheter embolectomy:
- Consider in those with thrombolysis contraindications or failure, or deemed unstable for medical management.
- Case-by-case basis
MEDICATION
- Alteplase: 100 mg (peds: N/A) IV over 2 hr
- Enoxaparin: 1 mg/kg (peds: 0.75 mg/kg) SC q12h
- Reteplase: 10 U (peds: N/A) IV bolus q30min × 2
- Streptokinase: 250,000 U (peds: 3,500–4,000 U/kg) IV bolus over 30 min, then 100,000 U (peds: 1,000–1,500 U/kg) IV maintenance over 24 hr
- Unfractionated heparin:
- Bolus: 80 U/kg (peds: 75 U/kg) IV over 10 min
- Maintenance: 18 U/kg (peds: 20 U/kg) IV drip
- Do not use TBW to calculate dose in obese patients.
- Warfarin: 5 mg (peds: 0.05–0.34 mg/kg/d) PO per day, adjust for INR goal 2–3
- Rivaroxaban: 15 mg BID × 3wks then 20mg QD
[Outline]
- Kline JA, Courtney DM, Kabrhel C, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost. 2008;6(5):772–780.
- Stein P, Fowler S, Goodman LR, et al. Multidetector computed tomography for acute pulmonary embolism. N Eng J Med. 2006;354:2317–2327.
- Stein PD, Woodward PK, Weg JG, et al. Diagnostic pathways in acute PE: Recommendations of the PIOPED II investigators. Am J Med. 2006;119:1048–1055.
- van Belle A, Büller HR, Huisman MV, et al. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography. JAMA. 2006;295(2):172–179.
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