Pregnancy is a sample of virchows triad .

1. In the name of GodDiagnostic Imaging of Pulmonary Embolism during pregnancy .Dr.MaryamMoradi

2. Pregnancyis a sample of virchowstriad. Risk for venous thrombo-embolism increased by a factor of four. Greatest risk is in postpartum period. PE leading cause of maternaldeath in developed countries

3. Evaluating the clinicalprobabilityis not possible No specific score for pregnant/post-partum patients Physiologic changes of pregnancycanmimicsigns and symptoms of embolism Clinicaldiagnosis or suspicion?

4. Lab data? • D-dimer which is the most frequent laboratory test in normal population with suspected PTE has not acceptable efficacy because in normal pregnancy D-dimer is usually increased . • Even though normal D-dimer levels seem to be rarely expected , especially in late pregnancy, europeanguidlines asserted that normal D-dimer levels can rule out PTE in pregnancy . • however this is not essentially supported by American thoracic society (ATS) concerning a retrospective study and 2 case reports which found negative D-dimer in confirmed cases of PTE which were pregnant

5. Missing the diagnosis of PTE carries high mortality rate. As mallick et al reported, undiagnosed PTE has a mortality rate of 30% which decreased to 2-8% in diagnosed and properly treated patients.

6. In the other hand, false positive diagnosis carries potentially side effects and consequences. A diagnosis of PTE for a pregnant mother posses some important implications including need for long-term anticoagulation, avoidance of breast feeding if an oral anticoagulants is used,the potential need for prophylaxis during future pregnancies and concern about future oral contraceptive use • Anticoagulation with heparin is the mainstay of treatment in pregnancy however it is not devoid of any side effect

7. Lower limb ultrasonography Not consensual STR/ATS Recommendation (RSNA 2010): only if symptoms of DVT CXR Then Lung Scintigraphy (LS) or CTA? Still debated What diagnostic algorithm?

8. Both fleischner society and British thoracic society guidelines agree that PCTA is the first imaging test of choice in general population who are suspected to have PTE , however non of them indicate that which technique is preferred in pregnancy

9. Ridge et al had noticed considerable number of PCTA studies in pregnant women which had poor quality resulted in inadequacy of test and repetition of examinations.

10. Higher rate of inconclusive CTA

11. Why?

12. Cardiac out put increases during pregnancy to about 50% above non pregnant levels and this leads to earlier arrival and stronger dilution of contrast material . • Poor opacification • Increasedblood volume • +50% @ 36 weeks, return to normal 6 month post-partum • Increasedpulsatility, poormixing

13. Respiratory physiological changes of pregnancy is other point of notice , leading to more artifactual images in pregnant women and contribute to impairment in good arterial opacification , because deep inspiration in pregnant women may increase influx of non opacified blood via inferior vena cava into the right heart . This effect can disappeared by valsalva maneuver or request the patient to do shallow inspiration during exposure .

14. deep inspiration • IncreasesInferior • Cavalblood flow • (non-opacifiedblood)

15. Poor opacification: risk of false positive

16. How to perform CTA? • Two crucial objectives • 1- Low rate of non-diagnostic results • Optimizing opacification • 2- Low radiation dose • Lowbreast radiation dose

17. Optimizing opacification • Three RULES • 1-Use sufficient amount of contrast • 2-Avoid deep inspiration • 3-Better timing use bolous triggering

18. All these factorscan further optimize the quality of pulmonary CTA in pregnant patients • It is now time to adapt our protocols and • provide optimum care for this sensitive patient group. 1-bolus triggering with short start delays, 2-high flow rates 3-High contrast concentration, 4- use of fast scanners and 5- low kVp scanning techniques..

19. Optimizing opacification • Use sufficient amount of contrast • At least 100 cc • Flow rate 4-6cc/min

20. Avoid deep inspiration • IncreasesInferior • Cavalblood flow • (non-opacifiedblood) Optimizing opacification

21. Deep inspiration Shallow breathing

22. Radiation dose optimization • Acquisition parameters • Shielding • Bismuth shielding • Lead shielding

23. Acquisition parameters • Limitation in Z axis • Pitch, mA, kV, rotation time • Adaptation of parametersdepends on CT unit manufacturer • Siemens: radiation dose is not lowerwithhigher pitch • GE: dose modulation: requiresincreasing noise index • Check estimated DLP • (Reduction in Z axis, 200 mA, 100kV) • mean effective dose: 5.21±1.54 mGy

24. Bismuth SHIELDING • Used for pediatrics(Fricke et al AJR 2003)

25. Bismuth SHIELDING • For adults • Controversial data • Hurwitz et al AJR 2009: 55% dose reductionwithoutqualityloss • Yilmaz JCT 2007: 40% dose reductionwithoutqualityloss • Vollmar et al EurRadiol 2008: 50% dose reductionwith noise increase (+ 40% ) and artefacts

26. Leadshielding • For fetal dose reduction(negligible) • Does not stop trans- diaphragmatic diffusion • Barium ingestion…

27. LS:Recommended if chest radiography is normal (CAHILL et al Obstet Gynecol. 2009 ) And no history of asthma, no alternative diagnosis suspected, available CTA: Recommended by the Fleishner society after negative US LS/CTA duringpregnancy

28. Comparison between PCTA and lung scintigraphy

29. Although diagnostic inadequacy of lung scintigraphy reported by Ridge is significantly less than PCTA (2.1% vs 35.7%) and Cahil et al found that non-diagnostic study is less for scintigraphy compared to CTPA (13.2% against 17%) ,however Revel reported no significant difference in the rate of indeterminate findings between two tests

30. Results

31. LS/CTA duringpregnancy • Similar performance • Scintigraphy • Lower breast radiation dose • CTA (more available in emergency) • Better agreement • Allows alternative diagnosis

32. Comparison of radiation

33. Shahir et al- AJR 2010: • The choice of studyshouldbebased on otherconsiderations, such as radiation concern, radiographicresults, alternative diagnosis, and equipmentavailability. Reducing the amount of radiation to the maternalbreastfavors use of perfusion scanning when the radiographicfindings are normal and thereis no clinical suspicion of an alternative diagnosis.

34. Lung Scintigraphy Not always available Breast radiation dose<<< CTA Inconclusive results < general population CTA Iodinated contrast medium: fetal thyroid dysfunction? Allows alternative diagnosis Inconclusive results > general population LS/CTA pros √ and cons ×

35. No riskbefore 16 weeks’ gestation • Not withiodinatedcontrast injection • Bourjeily et al. Radiology 2010: « Neonatalthyroidfunction: effect of a single exposure to iodinatedcontrast medium in utero » • 334 newborns, all had normal T4 levelatbirth Fetal thyroid dysfunction

36. Afterdelivery • Iodinatedcontrast medium injection and breast-feeding • «The verysmallpotentialriskassociatedwith absorption of contrast medium maybeconsideredinsufficient to warrant stoppingbreast-feeding for 24 h followingeitheriodinated or gadolinium contrast agents »

37. Summary PE suspicion duringpregnancy and post partum • No specific score, Ddimers not useful • Chestradiography must beperformed • Alternative diagnosis? Estimaterisk of inconclusive LS • When CTA performed • Has to be conclusive • no deepbreath /at least 100cc@4cc/s /startwith a 25 s delay • Low radiation dose • Z axis limitation, noise index increase, bismuth shiedling are good options!

39. Thankyou