In the name of God

Diagnostic Imaging of Pulmonary Embolism during

pregnancy .

Dr.Maryam Moradi

Pregnancy is a sample of virchows triad. Risk for venous thrombo-embolism increased by a factor

of four. Greatest risk is in postpartum period.

PE leading cause of maternal death in developed countries

Evaluating the clinical probability is not possible

No specific score for pregnant/post-partum patients

Physiologic changes of pregnancy can mimic signs and symptoms of embolism

Clinical diagnosis or suspicion?

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, european guidlines 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

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.

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

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?

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

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.

Higher rate of inconclusive CTA

General Population

Pregnancy Post-partum

5 to 10% Cahill et al -Obstet Gynecol 2009 17% Revel et al- JTH 2008

20%U-Kim-Im et al - Eur Radiol 2008 27.5%

Ridge et al - AJR 2009 32%

WHY?

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• Increased blood volume○ +50% @ 36 weeks, return to normal 6

month post-partum• Increased pulsatility, poor mixing

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 .

deep inspiration

Increases InferiorCaval blood flow (non-opacified blood)

Poor opacification: risk of false positive

How to perform CTA?

Two crucial objectives

1- Low rate of non-diagnostic resultsOptimizing opacification

2- Low radiation doseLow breast radiation dose

≈Three RULES 1-Use sufficient amount of contrast

2-Avoid deep inspiration

3-Better timing use bolous triggering

Optimizing opacification

1-bolus triggering with short start delays, 2-high flow rates 3-High contrast concentration, 4- use of fast scanners and5- low kVp scanning techniques..

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. Use sufficient amount of contrast

At least 100 cc Flow rate 4-6cc/min

Optimizing opacification

2.Avoid deep inspiration

Increases InferiorCaval blood flow (non-opacified blood)

Optimizing opacification

Deep inspiration Shallow breathing

Radiation dose optimization

Acquisition parameters

ShieldingBismuth shieldingLead shielding

Acquisition parameters

Limitation in Z axis

Pitch, mA, kV, rotation time○ Adaptation of parameters depends on CT unit

manufacturerSiemens: radiation dose is not lower with higher pitchGE: dose modulation: requires increasing noise index

○ Check estimated DLP

(Reduction in Z axis, 200 mA, 100kV) mean effective dose: 5.21±1.54 mGy

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

For adults Controversial data

○ Hurwitz et al AJR 2009: 55% dose reduction without quality loss ○ Yilmaz JCT 2007: 40% dose reduction without quality loss○ Vollmar et al Eur Radiol 2008: 50% dose reduction with noise increase (+ 40% ) and artefacts

Bismuth SHIELDING

Lead shielding For fetal dose reduction (negligible)

Does not stop trans- diaphragmatic diffusion Barium ingestion…

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 during pregnancy

Comparison between PCTA and lung scintigraphy

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

Result CTA LS p+ 16% (7/43) 11% (10/94) 0.35

- 65% (28/43) 68% (64/94) 0.73

? 19% (8/43) 21% (20/94) 0.72Need for othertest

5% (2/43)

7% (7/94)

0.42

AlternativeDiagnosis

28%(12/43)

0%

Kappa value

0.84(0.68- 0.99)

0.75 (0.63- 0.87)

Results

• Similar performance• Scintigraphy

• Lower breast radiation dose• CTA (more available in emergency)

• Better agreement• Allows alternative diagnosis

LS/CTA during pregnancy

Comparison of radiation

Shahir et al- AJR 2010:

The choice of study should be based on other considerations, such as radiation concern, radiographic results, alternative diagnosis, and equipment availability. Reducing the amount of radiation to the maternal breast favors use of perfusion scanning when the radiographic findings are normal and there is no clinical suspicion of an alternative diagnosis.

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 ×

• No risk before 16 weeks’ gestation

• Not with iodinated contrast injection

• Bourjeily et al. Radiology 2010: « Neonatal

thyroid function: effect of a single exposure to

iodinated contrast medium in utero »• 334 newborns, all had normal T4 level at birth

Fetal thyroid dysfunction

After delivery• Iodinated contrast medium injection and breast-

feeding

« The very small potential risk associated with absorption of contrast medium may be considered insufficient to warrant stopping breast-feeding for 24 h following either iodinated or gadolinium contrast agents »

SummaryPE suspicion during pregnancy and post partum

No specific score, Ddimers not useful

Chest radiography must be performed Alternative diagnosis? Estimate risk of inconclusive LS

When CTA performed Has to be conclusive

○ no deep breath /at least 100cc@4cc/s /start with a 25 s delay

Low radiation dose○ Z axis limitation, noise index increase, bismuth shiedling are good options!

Thank you