Pulmonary embolism in pregnancy

Background

  • Incidence of VTE in pregnancy and postpartum is 1.72 per 1000[1]
  • Risk significantly elevated in the 6 weeks postpartum
    • Risk of DVT equal in 1st and 2nd trimesters, higher risk in 3rd trimester and 3 weeks postpartum [2]
    • PE most commonly occurs in postpartum. [2]
    • Common risk factors include:
      • Advanced maternal age
      • C-Section
      • Obesity
      • Multiple gestations
      • Thrombophilia
      • Prior VTE
  • Risk returns to baseline by 12 weeks postpartum[3]
  • Consider MI in differential as risk can increase 3-6 times during the postpartum period

Clinical Spectrum of Venous thromboembolism

Only 40% of ambulatory ED patients with PE have concomitant DVT[4][5]

Chemical Prophylaxis

  • Lovenox 30mg SubQ q12 hrs (if Cr Clearance > 30)
    • Check AntiXa level every week EXACTLY 4 hours after 3rd dose of lovenox
      • prophylactic goal: 0.2-0.6
      • therapeutic goal: 0.6-1.2
  • Recheck AntiXa level after each 3rd dose if dose is changed until you are at goal
  • Recheck level every week (usually qMonday) for all patients
  • If renal dysfunction order heparin 5000 Units SubQ q8 hrs (search “SURG DVT/VTE prophylaxis” order set)

Pulmonary Embolism Categorization[6]

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)[7]

  • 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[8]
    • 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

Clinical Features

Symptoms

According to the PIOPED II study, these are the most common presenting signs[9]

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

Evaluation

Clinical Decision Rules

  • YEARS Algorithm appears to be possible viable clinical decision tool to rule out PE in pregnant patients [10]
    • utilizes d dimer test and presence of three YEARS criteria: clinical signs of DVT, hemoptysis, PE as most likely diagnosis
    • clinical sign of DVT with positive US LE, initiate anticoagulant treatment
    • clinical sign of DVT with negative US LE, into algorithm
    • No YEARS criteria with d dimer <1000, PE ruled out
    • No YEARS criteria with d dimer >1000, CTA
    • 1-3 YEARS criteria with d dimer <500, PE ruled out
    • 1-3 YEARS criteria with d dimer >500 , CTA

If clinical features suggestive of PE and lower extremity swelling

  • Begin with bilateral lower extremity duplex scan
    • if positive→treat empirically for PE
    • if negative→CTA
      • CTA and V/Q scans yield approximately 0.025 rad and 0.040 rad respectively to the fetus[11]
      • >5 rads is considered teratogenic[12]
      • However, 20-100 times more radiation is delivered to maternal breast tissue with CT, increasing the risk of breast cancer[13]
  • Up to 17% of pregnant patients have isolated pelvic DVT(not found with ultrasound)[14]
CT (with shield) vs. V/Q is roughly equivalent radiation exposure to fetus, but CT confers increased radiation to maternal breast tissue

American Thoracic Society In Pregnancy[15]

  • D-dimer is not recommended for excluding PE (weak recommendation, very-low-quality evidence).
  • If signs and symptoms of deep venous thrombosis (DVT), first perform bilateral venous compression ultrasound (CUS) of lower extremities, followed by anticoagulation treatment if positive and by further testing if negative (weak recommendation, very-low-quality evidence).
  • If no signs and symptoms of DVT, pulmonary vascular imaging should be used over bilateral lower extremity ultrasounds(weak recommendation, very-low-quality evidence).

D-Dimer

  • D-Dimer MAY BE used with following limits with very poor evidence[16][17][18]
    • 1st trimester: <750 ng/mL (+50% increase from normal lab threshold)
    • 2nd trimester: <1000 ng/mL (+100% from normal)
    • 3rd trimester: <1250 ng/mL (+150% from normal)
  • YEARS Algorithm
    • 3-month incidence of VTE of pregnant patients without CTPA was 0.43%[19]
    • Pregnancy-adapted YEARS algorithm recommends initiation of anticoagulation in positive US compression of symptomatic leg should there be signs of DVT
    • Pregnancy-adapted YEARS algorithm [20] “Pulmonary embolism was safely ruled out by the pregnancy-adapted YEARS diagnostic algorithm across all trimesters of pregnancy. CT pulmonary angiography was avoided in 32 to 65% of patients"
      • efficiency of algorithm highest during first trimester and lowest during third

Management

Disposition

  • Admit

See Also

References

  1. James AH, et al. Venous thromboembolism during pregnancy and the postpartum period: Incidence, risk factors, and mortality. 2006; 194(5):1311–1315.
  2. 2.0 2.1 Chan et al. Venous Thromboembolism and Antithrombotic Therapy in Pregnancy. SOGC Guidelines. 2014.
  3. Kamel H, et al. Risk of a thrombotic event after the 6-week postpartum period. N Engl J Med. 2014; 370:1307-1315.
  4. Righini M, Le GG, Aujesky D, et al. Diagnosis of pulmonary embolism by multidetector CT alone or combined with venous ultrasonography of the leg: a randomised non-inferiority trial. Lancet. 2008; 371(9621):1343-1352.
  5. Daniel KR, Jackson RE, Kline JA. Utility of the lower extremity venous ultrasound in the diagnosis and exclusion of pulmonary embolism in outpatients. Ann Emerg Med. 2000; 35(6):547-554.
  6. Jaff MR et al. Management of massive and submassive pulmonary embolism, ileofemoral deep vein thrombosis, and chronic thromboembolic pulmonary hypertension: a scientific statement from the American Heart Association. Circulation. 2011 Apr 26;123(16):1788-830. doi: 10.1161/CIR.0b013e318214914f. Epub 2011 Mar 21
  7. Martin C et al. Systemic thrombolysis for pulmonary embolism: a review. P T. 2016 Dec; 41(12):770-775
  8. Becattini C et al. Multidetector computed tomography for acute pulmonary embolism: diagnosis and risk stratification in a single test. Eur Heart J. 2011 Jul;32(13):1657-63. doi: 10.1093/eurheartj/ehr108. Epub 2011 Apr 18.
  9. Stein PD et al. Clinical characteristics of patients with acute pulmonary embolism: data from PIOPED II. Am J Med. 2007;120(10):871.
  10. van der Pol LM et al. Pregnancy-Adapted YEARS Algorithm for diagnosis of Suspected Pulmonary Embolism. NEJM 2019; 380(12): 1139-49
  11. Astani SA, et al. Detection of pulmonary embolism during pregnancy: comparing radiation doses of CTPA and pulmonary scintigraphy. Nucl Med Commun. 2014; 35(7):704-711.
  12. Bentur Y, Horlatsch N, and Koren G. Exposure to ionizing radiation during pregnancy: perception of teratogenic risk and outcome. Teratology. 1991; 43(2):109-112.
  13. Greer IA. Pregnancy complicated by venous thrombosis. N Engl J Med 2015; 373:540-547
  14. Chan WS, Spencer FA, Ginsberg JS. Anatomic distribution of deep vein thrombosis in pregnancy. CMAJ. 2010; 182(7):657- 660.
  15. Leung, A et al. An Official American Thoracic Society/Society of Thoracic Radiology Clinical Practice Guideline: Evaluation of Suspected Pulmonary Embolism PDF
  16. Kovac M. The use of D-dimer with new cutoff can be useful in diagnosis of venous thromboembolism in pregnancy. Eur J Obstet Gynecol Reprod Biol. 2010 Jan;148(1):27-30
  17. http://blog.ercast.org/2013/04/pulmonary-embolism-in-pregnancy/
  18. D-Dimer Concentrations in Normal Pregnancy: New Diagnostic Thresholds Are Needed. Kline et all. Clinical Chemistry May 2005 vol. 51 no. 5 825-829 http://www.clinchem.org/content/51/5/825.long
  19. Van Der Hull T et al. Simplified diagnostic management of suspected pulmonary embolism (the YEARS study): a prospective, multicentre, cohort study. Lancet. 2017 Jul 15;390(10091):289-297.
  20. van der Pol LM et al. Pregnancy-Adapted YEARS Algorithm for diagnosis of Suspected Pulmonary Embolism. NEJM 2019; 380(12): 1139-49
  21. 21.0 21.1 Tintinalli's 7th edition
  22. Stone SE and Morris TA. Pulmonary embolism during and after pregnancy. (Crit Care Med 2005; 33[Suppl.]:S294 –S300.

Authors:

Ross Donaldson