Pulmonary embolism

(Redirected from Pulmonary Embolism (PE))

See pulmonary embolism in pregnancy for pregnancy specific information.[1]

Background

Clinical Spectrum of Venous thromboembolism

Only 40% of ambulatory ED patients with PE have concomitant DVT[2][3]

Pulmonary Embolism Categorization[4]

Massive: High-risk

Hemodynamically unstable with symptoms of shock

  • ACCP 2016 CHEST Guidelines: Sustained hypotension ONLY criteria (systolic BP <90 for at least 15min or requiring inotropic support)
  • Previous definitions (e.g. AHA 2011) include cardiac arrest/pulselessness or persistent profound bradycardia (HR <40 with signs of shock)

Submassive: Intermediate-risk

Right ventricular dysfunction (RVD) and/or myocardial necrosis in the absence of persistent hypotension or shock (SBP >90)[5]

  • RV dysfunction
    • RV dilation or dysfunction on TTE
      • "D Sign" on bedside echo (LV takes on a "D" shape due to RV dilation)
    • RV dysfunction on CT defined as RV/LV ratio >0.9[6]
    • Elevation of BNP (>90)
    • ECG findings of right heart strain (see diagnosis below)
  • Myocardial necrosis: Troponin I >0.4

Non-Massive: Low-risk

No hemodynamic compromise and no RV strain

Sub-Segmental

  • Limited to the subsegmental pulmonary arteries

Epidemiology

  • The best estimates indicate that 350,000 to 600,000 Americans each year suffer from DVT and PE[7]
  • Survival[8]
    • PE is the 3rd leading cause of cardiovascular morbidity and mortality
    • At least 100,000 deaths per year may be directly or indirectly related to DVT and PE
    • For almost one quarter of PE patients, the initial clinical presentation is sudden death
    • PE is an independent predictor of reduced survival for ≤3 months
    • One of the leading causes of out-of-hospital, non-trauma related sudden deaths [9]

Clinical Features

Symptoms

According to the PIOPED II study, these are the most common presenting signs[10]

  • Dyspnea at rest or with exertion (73%)
  • Pleuritic chest pain (44%)
  • Cough (37%)
  • Orthopnea (28%)
  • Calf or thigh pain and/or swelling (44%)
  • Wheezing (21%)
  • Hemoptysis (13%)

Signs

  • Tachypnea (54%)
  • Calf or thigh swelling, erythema, edema, tenderness, palpable cord (47%)
  • Tachycardia (24%)
  • Rales (18%)
  • Decreased breath sounds (17%)
  • Accentuated pulmonic component of the second heart sound (15%)
  • JVD (14%)
  • Fever (3%)

Differential Diagnosis

Chest pain

Critical

Emergent

Nonemergent

Acute dyspnea

Emergent

Non-Emergent

Workup

Assessing Pretest Probability

  • Objective criteria (Geneva, Wells, etc.) is equal to gestalt in assessing pre-test probability[11] (ACEP Level B)
  • Initial Wells study and prospective validation [12] used a three tier system (low 0-1, intermediate 2-6, high >6) to establish pretest probability with a small sample size
  • The larger Christopher Study group used a larger sample size to derive the simplified dichotomized/two tier model below[13]

Wells Criteria

Clinical Features Points
Symptoms of DVT (leg swelling and pain with palpation) 3.0
PE as likely as or more likely than an alternative diagnosis 3.0
HR >100 bpm 1.5
Immobilization for >3 consecutive days or surgery in the previous 4 weeks 1.5
Previous DVT or PE 1.5
Hemoptysis 1.0
Malignancy (receiving treatment, treatment stopped within 6 mon, palliative care) 1.0
Two Tier Wells Score
  • Score 0-4 = PE Unlikely (12.1% incidence of PE)
    • Check D-dimer
      • If D-dimer positive then obtain CTPA or V/Q scan
      • If D-dimer negative, no further workup needed (0.5% incidence of PE at 3 month follow up)
  • Score >4 = PE Likely (37.1% incidence of PE)
    • Obtain CT Pulmonary Angiography or V/Q Scan

Low-Probability Testing in the ED

  • PERC Rule negative, then no further workup[11] (ACEP Level B)
    • Avoid CT pulmonary angiography in low pretest probability patients that are either PERC rule negative or have a negative d-dimer (ACEP choosing wisely)
    • D-dimer NPV is 99.5%[14]
  • PERC Rule positive, then D-dimer (see Moderate-Probability Testing below)[11] (ACEP Level B)
    • Can also consider using Wells score as above to determine further testing

Less common risk factors

  • HIV (protein wasting nephropathy)
  • Nephrotic Syndrome
  • SLE with anti-cardiolipin Ab
  • Exogenous hormones (specifically estrogen)
  • homozygous Factor V Leiden
  • Antithrombin III deficiency
  • Protein C deficiency
  • Protein S deficiency
  • Hyperhomocysteinemia

Evaluate bleeding risk (HAS-BLED)

  • HAS-BLED score (developed to evaluate bleeding risk for anticoagulation in Afib) can also identify patients with acute VTE at high risk for bleeding complications within 6 months[15]
Risk Factor Point
Hypertension 1
Abnormal renal and/or hepatic function 1 point each
Stroke 1
Bleeding tendency/predisposition 1
Labile INR on warfarin 1
Elderly (age >65 years) 1
Drugs (aspirin or NSAIDs) and/or alcohol 1 point each
  • When applied to VTE patients on vitamin K-antagonists, NOT DOACs (in first 6 months of treatment):
    • Score 0-2 = 1.3% incidence of major bleeds
    • Score 3+ = 9.6% incidence of major bleeds
  • Other bleeding risk models include the RIETE score (validated in patients taking VKA or rivaroxaban) and VTE-BLEED score (validated in patients taking warfarin and edoxaban).

Initial Management While Awaiting Workup[16]

  • based on ACCP 2016 Guidelines
Clinical suspicion Management
Low Do not treat with anticoagulation while awaiting diagnostic test results
Medium Treat with parenteral anticoagulation if the results of diagnostic tests are expected to be delayed ≥ 4 hours
High Treat with parenteral anticoagulation while awaiting diagnostic test results

Diagnosis

A large pulmonary embolism at the bifurcation of the pulmonary artery (saddle embolism).

Definitive Diagnostic Imaging

  • CTA Chest if GFR >60
  • V/Q scan if GFR <60
    • Will be nondiagnostic if patient has effusion, pneumonia, or other airspace disease
  • If imaging negative, perform additional diagnostic testing (e.g. lower extremity Doppler US, V/Q scan, and/or traditional pulmonary angiogram) prior to exclusion of VTE[11] (ACEP Level C)
    • A negative d-dimer in combination with a negative CTA theoretically provides a post-test probability of VTE less than 1%

Other Possible Diagnostic Findings

D Sign[17]
Hampton's Hump
  • ECG (abnormal in 70% of PE [18] and associated with an adverse prognosis[19])
    • Sinus tachycardia (most common)
    • New-onset atrial arrhythmias (e.g. atrial fibrillation)
    • New RBBB (complete or incomplete) [20]
    • QR pattern in V1
    • S1Q3T3 (RV strain pattern)
    • T-wave inversion in anterior/septal leads (V1-V4) + inferior leads[21]
    • ST segment changes in V1 through V4
    • New right axis deviation
  • CXR (abnormal in 70%)
    • Atelectasis is most common (esp >24 hrs after onset of symptoms)
    • Pleural effusion
    • Hampton's Hump
    • Westermark's sign[22]
  • Formal transthoracic echo or bedside cardiac ultrasound
    • Can help diagnosis in equivocal cases
    • May see signs of right heart strain (bowing of septum into LV; Aka D Sign)
      • Right ventricular strain is associated with statistically significant worse outcome[23]
    • McConnel's sign (akinesis of RV base/free wall with sparing of apex)
    • Lateral right ventricular wall diameter of <5mm is suggestive of acute pulmonary hypertension while >5mm is suggestive of chronic pulmonary hypertension[24]
  • SPECT
    • Combination of noncontrast CT chest with V/Q scan
    • Avoidance of contrast for patients with renal injury
    • As sensitive as CTPA and more sensitive than planar V/Q scanning[25]

Management

Supportive care

  • Oxygen therapy (maintain SpO2 ≥90% unless otherwise indicated)
  • Hemodynamic support (e.g. IVF, pressors)
    • Consider gentle fluid challenge of 500ml normal saline bolus to improve cardiac index in select patients[26]
    • Experimental studies suggest that aggressive volume expansion provides little benefit and may worsen RV function in those with acutely elevated RV afterload and acutely increased pulmonary HTN[27]

Anticoagulation

  • Always consider bleeding risk when determining risks/benefits of initiating anticoagulation
  • Treatment options include any of the following anticoagulations which are indicated for all patients with confirmed PE or high clinical suspicion (do not wait for imaging).
Name LMWH SC Unfractionated Heparin Dabigatran Rivaroxaban Apixaban Coumadin
Initial Dose
  • 80 units/kg bolus; then 18 units/kg/hr continuous infusion
  • Parenteral anticoagulation for 5-10 days; then 150mg twice daily
  • 15mg twice daily for 3 weeks, then 20mg once daily
  • 10mg twice daily for 1 week, then 5mg twice daily
  • Cannot be administered alone for acute PE. Usual starting dose 5mg PO
Benefits
  • 1st line for most hemodynamically stable patients
  • Preferred in those with cancer, liver disease, coagulopathy, pregnancy
  • Short half-life
  • Preferred if rapid reversal is needed (e.g. considering thrombolytics or with bleeding risk/trauma)
  • No need for renal dosing
  • Noninferior to warfarin in reducing DVT and PE [28]
  • Preferred if parenteral therapy to be avoided
  • Associated with less bleeding, particularly in elderly patients and those with moderate renal impairment compared to standard treatments [29]
  • Preferred if parenteral therapy to be avoided or if history of GI bleeding
  • Studies show 16% reduction in VTE related death compared to standard therapy [30]
  • Preferred in renal disease, history of poor compliance, or history of GI bleed
Contraindications
  • Severe renal impairment (CrCl <30 mL/min)
  • Patients with morbid obesity or anasarca may have poor absorption
  • Use with caution in patients >60yo
  • Previous history of HIT
  • Avoid in CAD and in severe renal impairment
  • Avoid in hepatic disease (Child-Pugh Class B/C)
  • Avoid in severe hepatic disease and renal impairment
  • Temporary hypercoagulable state for approx 5 days
Comments
  • Dose adjustments may be necessary in obese patients
  • Check PTT after 6hr; adjust infusion to maintain PTT at 1.5-2.5x control
  • Consider interactions with CYP3A4 inhibitors (e.g. -azoles)
  • Consider interactions with CYP3A4 inhibitors
  • INR target 2.5
  • Consider many drug-drug interactions with CYP450 inhibitors or inducers
  • Duration
    • 3-6 mo, if time limited risk factor (post-op, trauma, estrogen use)
    • 6 mo to life, if idiopathic etiology or recurrent

Subsegmental PE

  • Evaluate for proximal DVT in legs with ultrasound
    • If low risk for recurrent VTE: Clinical surveillance recommended over anticoagulation (Level 2C evidence)[31]
    • If high risk for recurrent VTE: anticoagulation recommended over surveillance

Catheter-directed Therapy for intermediate-risk (submassive) PE[32]

  • Includes catheter-directed thrombolysis and mechanical thrombus removal without thrombolysis
  • Still no large prospective cohort or randomized trial evaluating CDT, so limited evidence recommendations from ACCP 2016 are weak
    • Primary outcome measure in study of 59 patients was improved RV function at 24 hours, but not mortality
  • Given broad clinical spectrum of intermediate-risk PE, CDT can be considered in a subset of patients with following characteristics:
    • Intermediate-risk PE with more severe degree of RV dysfunction and positive biomarkers
    • Intermediate-risk PE with severe hypoxemia
    • High-risk (massive) PE with contraindications to systemic thrombolysis
  • Complications include major access site bleeding, significant arrhythmias, pulmonary artery dissection, tamponade, worsening hemodynamics

Thrombolysis

IVC Filter

  • Indications
    • anticoagulation contraindicated in patient with PE
    • failure to attain adequate anticoagulation during treatment

Disposition

  • Patients with significant clot burden generally require admission for anticoagulation
  • Consider discharge in low risk patients with peripheral PE[33]
  • Consider calculating HESTIA criteria for treatment of outpatient PE[34]

Prognosis

The Pulmonary Embolism Severity Index (PESI)[35]

  • PE patients with PESI class I or II seem safe to manage as outpatients.
Prognosis Variable Points Assigned
Demographics
Age +Age in years
Male +10
Comorbid Conditions
Cancer +30
Heart Failure +10
Chronic Lung Diseae +10
Clincal Findings
Pulse >110 b/min +20
sBP < 100 +30
RR > 30 +20
Temp <36 C +20
AMS +60
Art O2 Saturation <90% +20
Risk Class 30-Day Mortality Total Point Score
I 1.60% <65
II 3.50% 66-85
III 7.10% 86-105
IV 11.40% 106-125
V 23.90% >125

See Also

EBQ:Thrombolysis in Pulmonary Embolism Metanalysis

External Links

References

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Authors:

Ross Donaldson