Pregnant females are physiologically hypercoagulable making them five to ten times more likely to form a thrombus . The classic signs and symptoms of a pulmonary embolism such as dyspnea , tachycardia and lower extremity edema are seen normally during pregnancy . This results in unreliable risk stratification algorithms which cannot be accurately applied to pregnant patients . D-dimer fluctuates during pregnancy and false positive results are common in pregnancy . D-dimer is typically normal during the first trimester , rises during the second trimester and decreases after delivery reaching normal levels at four to six weeks postpartum . However , negative d-dimer has been useful in ruling out a pulmonary embolus in pregnant and postpartum patients .
Pregnant Patient
� Obtain CXR
� Hemodynamically stable ?
Yes No
Lower extremity compression ultrasound Perform CT pulmonary angiogram ( CTPA ) or VQ Scan with chest x-ray
|
Negative
Consider CT Pulmonary angiogram or VQ scan
|
Positive |
Negative CTPA or Negative VQ scan
PE Excluded
|
Negative CTPA or Low Probability or Intermediate VQ scan |
Positive CTPA or Moderate or High Probability VQ Scan
PE Confirmed : Treat unfractionated or fractionated heparin
|
PE Confirmed : Treat with low molecular weight heparin ( preferred ) or unfractionated heparin : Admit
Lower extremity compression ultrasound
Table 2 : Estimated Fetal Radiation Exposure :
Radiology exam |
Estimated fetal Radiation Exposure ( rad ) |
Thoracic spine radiograph |
< 0.001 |
Chest ( PA / lateral ) |
0.001 |
CT head |
< 0.01 |
Hip radiograph |
0.13 |
Pelvis radiograph |
0.17 |
abdominal radiograph |
0.24 |
lumbar spine radiograph |
0.34 |
CT abdomen / pelvis |
1-2 |
Ventilation Perfusion Scan |
0.06 - 1.0 |
CT chest Angiogram |
2 - 4 |
VQ Scan |
37-54 mrads |
Microcephaly , Mental Retardation thought to arise after 10-20 rad |
exposure |
Anomalies , IUGR , miscarriage rare < 5 rads |
Creasy RK , Resnik R , et al maternal-fetal medicine principles and practice |
6th edition |
Negative for DVT
DVT Excluded : consider other diagnosis
Positive for DVT
DVT Confirmed : Treat unfractionated or Fractionated heparin
The radiation dose to the fetus during a ventilation-perfusion scan ( V / Q scan ) has been estimated to be 100-300 mGy and 280 mGy to the mother ’ s breast . Both computed tomography pulmonary angiography ( CTPA ) and the ventilation / perfusion ( V / Q ) scan involve exposure to ionizing radiation . The effect of low-level ionizing radiation remains an issue of some controversy . CTPA delivers a greater effective dose and , in particular , greater doses to breast tissue , than the V / Q scan ( typically 10-70 mGy for CTPA vs < 1.5 mGy for V / Q to breast ). Since breast tissue is particularly radiosensitive in younger women , the V / Q study has an advantage over CTPA in this group . In the pregnant patient , fetal exposure has been raised as a concern . In fact , there is typically only low fetal exposure from either study (< 1 mGy ). The CTPA does deliver less fetal exposure , particularly in the first trimester , but the difference between CTPA and V / Q scan is small when compared with the difference in dose to maternal breast . The oncogenic risk of radiation to the fetus is considered dangerous at 0.01 Gy above background radiation which represents a 0.01 % increase in risk of cancer before the age of 20 years . The radiation dose from the combination of a chest x-ray , ventilation-perfusion scan and conventional pulmonary angiogram to the fetus is 0.004 Gy .( 2 )
Pulmonary Embolus 3