Issues in diagnosis of VTE in Pregnancy

Ng Heng JooDepartment of HaematologySingapore General Hospital

Does she or does she not…..

Doctor,My legs are getting more swollen. Maybe a little bit more on one side…..

SIGHHHH!

Suspected VTE in pregnancy– Diagnostic Difficulties

• Physiological changes commonly mimic symptoms/signs of VTE

• Clinical diagnosis insensitive and non-specific• Predictive scoring systems have not been

validated in pregnant women (e.g Wells)• Clinicians and parents may be reluctant to

subject patients/fetus to radiation from diagnostic test

Outline

• Diagnosis of DVT– Compression ultrasound– D-dimers– Predictive scores

• Diagnosis of Pulmonary Embolism– VQ scans vs CT scans– Predictive scores

What would we do if she were not pregnant?

• Consider the clinical likelihood of DVT – pre-test probability score (Wells score…

• D-dimer if score is low• Scan if score is high

Wells Score

Not valid for p

regnant patients

Ann Intern Med 2009

• L – Symptoms in the left leg• E – Edema, calf circumference difference >2 cm• Ft – First trimester

• Score 0 – 0%• Score 1 – 16%• Score 2-3 – 58%

LEFt validation

LEFt Clinical Prediction Rule

• Cannot be used as a standalone• Needs further validation in larger study

populations

D-dimers in normal pregnancy

• Using higher cut-points than those used in non-pregnant patients, the specificity of D-dimer assays for the diagnosis of DVT in pregnancy can be improved without compromising sensitivity. Validation in prospective management studies is needed

Imaging techniques

• Compression ultrasound• Magnetic resonance venography• Ascending contrast venography

Compression ultrasound

• Current standards• High sensitivity and specificity (>95%) for thigh

DVT• Less sensitive for pelvic vein and calf vein DVT• Colour Doppler, Valsava maneuver, decubitus

position etc improves diagnostic sensitivity for pelvic vein thrombus

• Calf vein thrombus – serial scans may detect progression to proximal vessels

Magnetic resonance venography

• High sensitivity for thigh and pelvic vein thrombosis in non-pregnant

• Limited data in pregnant women• Some evidence of potential value in pregnant

women

Diagnostic algorithm for DVT

ACCP 2012

Diagnostic Algorithm for PE

M. Tan, M.V. Huisman / Thrombosis Research 127 (2011)

Suspected pulmonary embolism

Modalities

• Pre-test probability scores – Not validated for pregnancy

• D-dimers – similar issues with suspected DVT• Imaging studies

Compression ultrasound of lower limbs

• Rationale– Treatment of DVT and PE is going to be the same– Potential to avoid exposure to radiation with PE

specific scans• Reality– Compression ultrasound as first investigation only

if there is clinical suspicion of DVT– Negative scans does not preclude other imaging

studies if PE symptoms present

CT scan vs VQ scans

Radiation exposure concerns - Fetus

• Malformations have a threshold of 100-200 mGy or higher and are typically associated with central nervous system problems

• Fetal doses of 100 mGy (0.1Gy) are not reached even with 3 pelvic CT scans or 20 conventional diagnostic x-ray examinations

• Perfusion scintigraphy exposes the fetus to around 0.2 mSv

• Multi detector row helical CT: 0.013 mSv

ICRP 84

Radiation exposure to fetus by procedure

Radiation exposure concerns - Mother

Radiation absorption by maternal breast tissue• CT scan: 10 mGy• V/Q scan: 0.28 mGy• 1 mGy of radiation exposure is associated with

an increase of breast cancer by an additional 1 in 50,000 women

CT scan vs VQ scans• Diagnosing pulmonary embolism in pregnancy using computed-

tomographic angiography or ventilation-perfusion.Cahill AG, Stout MJ, Macones GA, Bhalla S. Obstet Gynecol. 2009;114(1):124.

• Pulmonary embolism in pregnancy: comparison of pulmonary CT angiography and lung scintigraphy. Ridge CA, McDermott S, Freyne BJ, Brennan DJ, Collins CD, Skehan SJ. AJR Am J Roentgenol. 2009;193(5):1223

• Pulmonary embolism during pregnancy: diagnosis with lung scintigraphy or CT angiography? Revel MP, Cohen S, Sanchez O, Collignon MA, Thiam R, Redheuil A, Meyer G, Frija G. Radiology. 2011;258(2):590.

• Pulmonary embolism in pregnancy: CT pulmonary angiography versus perfusion scanning. Shahir K, Goodman LR, Tali A, Thorsen KM, Hellman RS. AJR Am J Roentgenol. 2010;195(3):W214.

CT scan = VQ scan

MRI scan

• No ionizing radiation• Misses subsegmental PE• Not well validated• Uses gadolinium which crosses placenta

RCOG 2015

Thank you