A 32F who is 14 weeks pregnant presents with intermittent shortness of breath x 1 day. She has no h/o DVT/PE. Vitals 98.9 100  105/70  18  99% on RA.  Clear lungs, no calf asymmetry on exam. You are concerned about PE. How should you proceed? If she needs imaging, CTA or V/Q?

The incidence of venous thromboembolic disease in pregnancy is 1 in 1000.  There is about a 2-to-5 fold increased risk of VTE  in all trimesters over non-pregnant, age-matched women. And that risk shoots to about 30 fold in the week after delivery.

One evidence-supported approach to avoiding radiation is the following:

1) Get bilateral LE dopplers. If it’s positive, you’re done, she gets anticoagulated.

2) Apply the PERC rule AND obtain a d-dimer (yes, both). For the PERC rule, use a pregnancy-adjusted HR of <105. Then there are pregnancy-adjusted dimer levels: 1st trimester 750 ng/dL, 2nd 1000 ng/dL, and 3rd 1250 ng/dL.  If she PERCs out and has a dimer lower than these thresholds, then you’re done.

3) If she screens in then the safest imaging modality is actually CT angiogram. V/Q scanning exposes the fetus to more radiation as the technetium sits in the bladder (in fact, pts who require a V/Q need to get a Foley beforehand).

Obviously with positive results, you get OB involved. Lovenox appears to be the preferred drug.  Pts usually get anticoagulated until 6 weeks post-partum.

Elliot, CG. Journal of Thoracic Imaging: Volume 27(1), January 2012
Tufano, A. Semin Thromb Hemost 2011; 37(8): 908-917
University of Maryland, Dept of Emergency Medicine website