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Investigation of suspected pulmonary embolism in pregnancy

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Investigation of suspected pulmonary embolism in pregnancy

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Investigation of suspected pulmonary embolism in pregnancy

  1. 1. PE in Pregnancy Dr Chantelle Badawy ED Registrar – CME - SCGH
  2. 2. PE in Pregnancy
  3. 3. Epidemiology The risk of PE in the non-pregnant female risk is 1 in 100,000, this increases to 1 in 10,000 in pregnant age-matched females. PE occurs in 1 of 1600 pregnancies PE during pregnancy may be fatal in almost 15% of patients, and in 66% of these, death will occur within 30 minutes of the embolic event.(RCOG) PE is a leading cause of Maternal mortality in the developed world In Australia, the leading causes of direct maternal deaths  (when combined = ¾ all maternal deaths)  amniotic fluid embolism (9),  thromboembolism (8),  obstetric haemorrhage (7)  eclampsia (6), Sepsis and cardiac conditions were the leading causes of maternal death for Indigenous Australians.
  4. 4. Why is this so important? VTE is a significant cause of morbidity and mortality during pregnancy. The clinical evaluation alone cannot confirm or refute a diagnosis of VTE in the non-pregnant population, and diagnosing VTE during pregnancy is more challenging. Ultimately - nobody “WANTS” to perform a peri-mortem cesarean
  5. 5. Why is it difficult to evaluate? Difficulty and confusion arises in the work up of PE in the pregnant patient due to 3 things: 1.The normal physiological changes in pregnancy; dyspnoea, tachycardia and leg swelling are also common PE symptoms    2.The pre-test probability score, (Wells & PERC), cannot be used in a pregnant patient as they were excluded from the analysis group for criteria validation. 3.The d-dimer will rise in the second trimester and remain elevated for 4-6 weeks post-partum. The diagnosis of VTE during pregnancy often is impaired by a reluctance to expose a pregnant patient and her fetus to radiation.
  6. 6. Multiple Risk factors at play… 1)Pregnancy itself is a risk factor 2)Prev VTE in pt on hormonal contraception 3)Prev VTE during pregnancy (risk 12%) 4)Rheumatic heart disease and pts with heart prosthesis 5)Thrombophilia's 6)Age > 35yrs 7)Obesity BMI > 30 8)Multi-parirty >4 9)Recurrent miscarriage 10)Bed rest & physical immobility 11)Hyperemesis gravidarum 12)Shock & dehydration 13)Infection Why is it difficult to evaluate?
  7. 7. The pregnant patient fulfills all of Virchow’s triad Emboli cause respiratory compromise due to lack of perfusion of ventilated lung and heamodynamic compromise due to increased pulmonary arterial resistance Pathophysiology
  8. 8. Diagnosis of PE & DVT Diagnosis of pulmonary embolism Clinical presentation Pre-test probability Routine lab evaluation ABG ECG CXR D Dimer Ultrasound CTPA VQ Scan
  9. 9. Diagnosis – Clinical Sympotms The classic symptoms of VTE are less specific during pregnancy than during the non-pregnant state. Sweating (18%) Dyspnea (62%) Pleuritic chest pain (55%) Cough (24%) Tachycardia & palpitations Tachypnoea Leg swelling & pain Haemoptysis There are no clinical S&S that are specific for PE, esp in pregnancy. Consider that dyspnoea occurs in up to 70% of all normal pregnancies Clinical suspicion must remain high, and the appropriate diagnostic workup should ensue.
  10. 10. Diagnosis – Pre-test Probability There is no evidence for the use of (WELLS) pretest probability assessment in the management of acute VTE in pregnancy. Pregnant patients were excluded form the validation trials and therefore no supporting data Modified Wells which takes into account leg circumference and trimester has a high sensitivity & specificity though there is not enough data to put this to use at this point. Unfortunately, the PERC rule has not been validated in pregnancy either. Kline is in the process of validating a modified PERC for pregnant patients, to be used with HR >105 & applied to low risk patients to risk – however this lacks evidence at this stage
  11. 11. Diagnosis - ABG Limited diagnostic value (for pregnant & non-pregnant) Resp alkalosis is common in both pregnancy and PE. In one study, ABG analysis showed that only 10% had arterial PO2 levels less than 60 mmHg and 2.9% had oxygen saturation levels less than 90%. The presence of hypoxaemia and normal CXR should raise the suspicion for PE in pregnancy
  12. 12. Diagnosis - ECG The ECG changes associated with acute PE may be seen in any condition that causes acute pulmonary hypertension, including hypoxia causing pulmonary hypoxic vasoconstriction. One study found that the ECG was abnormal in 41% of women with acute PE; the most common abnormalities were  T wave inversion (21%), S1Q3T3 pattern (15%) Right bundle branch block (18% during pregnancy and 4.2% in the puerperium). Given the increasing incidence of IHD in pregnancy, the ECG may also be helpful in identifying alternative diagnoses
  13. 13. 1) Sinus tachy RBBB T-wave inversions in the right precordial leads (V1-3) as well as lead III
  14. 14. 2) RBBB Extreme right axis deviation (+180 degrees) S1 Q3 T3 T-wave inversions in V1-4 and lead III Clockwise rotation with persistent S wave in V6
  15. 15. Diagnosis - CXR Exclude or diagnose other pathology Eg – pneumonia, pneumothorax or lobar collapse. CXR is normal in >50%pt with proven PE. Abnormal features caused by PE include atelectasis, effusion, focal opacities, regional oligaemia or pulmonary oedema. Normal CXR prior to V/Q scanning improves the likelihood of a definitive V/Q result.  If the CXR is abnormal with a clinical suspicion of PE, CTPA should be performed.
  16. 16. Diagnosis – D Dimer Currently, the general consensus is still that D-dimer is not an adequate enough test to rule-out a pulmonary embolism in a pregnant patient.   D Dimer 60% of healthy patients in normal pregnancy will have a raised D- dimer A ‘positive’ D-dimer test in pregnancy is not necessarily consistent with VTE. The role of D-dimer testing in the investigation of acute VTE in pregnancy remains controversial. Kline proposes that an altered “normal value” in pregnancy is useful First trimester - 50% above upper limit Second trimester – Double the upper limit Third Trimester - 2.5 times the upper limit
  17. 17. Diagnosis – Compression Ultrasound DVT are the source of more than 95% of PE and the prevalence of PE correlates with predisposition to leg thrombosis - hence if you find a leg DVT on US you can stop investigating (also given the DVT & PE treatment are the same) This strategy has been evaluated in a prospective cohort study of 221 pregnant women who presented with suspected DVT.’ Sensitivity of serial doppler - 94.1% (95% CI 69.2–99.7%) Diagnosis of deep vein thrombosis Ultrasound – Sensitivity 97% & Specificity 94% No radiation exposure
  18. 18. Diagnosis - VQ Scan The amount of radiation exposure varies based on the isotope used, but VQ scanning can be performed safely during pregnancy. It is possible to exclude the initial Ventilatory (V) phase of the scan (if normal CXR) and therefore reduce the radiation exposure. Many authorities continue to recommend V/Q scanning as first- line due to in its high negative predictive value & its substantially lower radiation dose to pregnant breast tissue
  19. 19. Diagnosis - CTPA CTPA has potential advantages over V/Q imaging including: CTPA is more readily available, Delivers a low radiation dose to the fetus Can identify other pathology There is a theoretical risk of hypothyroidism for neonates who have been exposed in utero contrast** Suggest IDC & IV Fluid to “flush” the contrast rapidly and avoid excessive exposure time to feotus - contrast crosses placenta & collects in amniotic fluid.  The radiation exposure is comparable to that of VQ scan and is within the amount considered to be safe in pregnancy.
  20. 20. MRI The use of MRI to diagnose acute PE has been explored but is not recommended for routine diagnosis of PE. Gadolinium should not be used in pregnancy where possible
  21. 21. Test Whole body rad (mSv) Risk to mother (mGy) Risk to Feotus (mGy) CXR 0.07 0.01 CTPA 1.6-8.3 Lung 39.5 Breast 10-60  each trimester 3.3 – 130  risk breast Ca >10mGy by 13.6%* above BG risk VQ Scan Q alone 1-2.5 0.8 Lung 5.7–13.5 Breast 0.98-1.07 Constant each trimester 0.3 – 7.4 Predictive models show  lifetime risk Breast Ca CTPA than VQ Bg rad / year 2.5 Dose 100mGy = <1% risk childhood Ca Max allow rad exp /yr 50 (Avge = 20) Conversion mSv- effective dose (tissue wt factor/ or absorbency) mGy- qant absorbed dose *13.6% of 0.1% risk in 25yo = 0.0136% extra risk (very little)
  22. 22. How to understand the Radiation exposure to fetus (Kline) Threshold for dangerous radiation 0.1Gy = $100  (greater than this is believed to be excessive & possibly cause congenital abnormalities) Fetal absorbed CXR is 0.1 Cent CTPA 25-50 Cents VS VQ – 50-75 Cents BG radiation to fetus over 9 months $5 Radiation to increase lifetime Ca risk before age 20 by 1 in 10 000 is $10 Argued that there is no reliable way to measure these doses and effects in utero. Exposure to Mum – age you about 3 years (ie equivalent to 3yrs normal background radiation)
  23. 23. DOHWA Imaging Pathway
  24. 24. Suggested Pathway (ATS)
  25. 25. Treatment UFH (Pregnancy Cat C) & LMWH (Pregnancy Cat C) can be used in pregnancy IV Heparin immediately before delivery is ideal given is short half life. Heparin does not cross the placenta & does not carry risks for teratogenesis and fetal hemorrhage, although bleeding at the uteroplacental junction is possible. - Warfarin (Pregnancy Cat D) crosses the placenta, is teratogenic and are contraindicated during some stages of pregnancy, In the initial management of DVT, the leg should be elevated and a graduated elastic compression stocking applied to reduce oedema. Mobilization with graduated elastic compression stockings should be encouraged.
  26. 26. Treatment – unstable Massive PE may present with shock, refractory hypoxaemia and/or right ventricular dysfunction on echocardiogram and is a medical emergency. Collapsed, shocked women who are pregnant or in the puerperium should be assessed by a multidisciplinary resuscitation team of experienced clinicians Supportive care and intravenous anticoagulation should be instituted without delay. Subsequent treatment options are controversial and include IVC filter placement, thrombolytics, and embolectomy. Sudden death, cor pulmonale, or cardiovascular collapse occurs when 60% or more of the pulmonary circulation is obstucted with emboli
  27. 27. PIOPED II Study  Study question – Clinically suspected acute PE, what is the diagnostic accuracy of CTPA?  PIOPED II (2006) is the largest study to date which compared CTPA against a composite reference standard and demonstrated an 83% sensitivity and 96% specificity in detecting an acute PE.  PIOPED II suggested that the predictive value of CTPA is highly concordant with the pretest clinical probability of PE using Well's criteria.  Design - Prospective, multicenter(8) , comparison study (7,284 screened, 3,262 eligible, 1,090 enrolled)over 2001-2003  N=824 completed evaluation for diagnosis of PE by both:  Composite reference standard, and  CT angiography ***Interestingly, “Possible Pregnancy” was an exclusion criteria for this study
  28. 28. PIOPED II Study Made the following recommendations 1.D Dimer with clincal assessment should be obtained 2.If D-Dimer is positive, venous Ultrasound is recommended before using radiaiton imaging 3.69% of PIOPED II investigators recommend Pulmonary VQ scan and 31% recommend CTPA.  Stein PD, et al. "Multidetector Computed Tomography for Acute Pulmonary Embolism". The New England Journal of Medicine. 2006. 354(22):2317-2327.
  29. 29. Kline : Systematic review and meta-analysis of PE in Prengnacy (May 2014)  Methods:  Studies in all languages from multiple databases in Feb 2014, ED pts with possible PE  Outcome of VTE+ ( DVT or DVT&PE)  Papers were assessed for selection and publication bias, and heterogeneity  Findings:  Seventeen full-length studies of 25,339 patients were analysed.  The frequency of VTE+ rate among the 506 pregnant patients was 4.1% (2.6- 6.0) compared with 12.4% (9.0-16.3) among non-pregnant patients.  The pooled RR of pregnancy for VTE+ diagnosis was 0.60 (0.41-0.87).  Patients in the third trimester had an RR of 0.85 (0.40, 1.77) and patients of childbearing age(≤45 years) had an RR of 0.56 (0.34 to 0.93).  Interpretation:  In the ED setting, physicians test for PE in pregnant patients at a low threshold, resulting in a low rate of VTE diagnosis (4.1%, 95% CI: 2.6-6.0)  Relative risk of VTE that is lower than non-pregnant women of childbearing age who are tested for PE in the ED setting.
  30. 30. Summary Higher risk of PE in pregnancy – must have clinical suspicion Wells & Perc have not been proven in pregnancy D Dimer is limited value unless alter cut off values (controversial) Always consider Lower limb ultrasound first – if POS then treat. If NEG keep looking If no limb symptoms or USS Neg perform CXR VQ Scan (esp Perfusion phase only) presents less radiation risk CTPA is useful if CXR abnormal When in doubt, treat until confirm/refute diagnosis Engage multiple team members in decisions, keep the patient well informed and discuss radiation risks openly
  31. 31. References

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