What is the best initial step for diagnosis of PE in pregnancy?

[SlaveOfTCMC]

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Assuming high pre-test odds: (pleuritic chest pain, dimnished O2sats, tachypnea)

Spiral CT or Pulmonary Angiography?

We all know the angiography is the BEST TEST

And some sources have said that in pregnancy, you go straight for the BEST TEST

But I do not know the reasoning behind that.. or if this is even indeed the initial step.

Can anyone shed some light please?



On another related note about PE:

In real life and in the guidelines, it says for anyone who has high suspicion for PE or DVT, give anticoagulation (e.g. heparin) empirically. Diagnostic workup should NOT get in the way of empiric treatment

Yet some of the qbanks seem to imply that you should ALWAYS GET A DIAGNOSIS FIRST before treatment.

Thus I am left scratching my head

 

[turkeyjerky]

Whew, this is a tough one. Of the two, I would certainly get the CT prior to invasive angiography. While it's touted as the 'gold standard', it's invasive and has a mortality rate of .5-1%. It's also not particularly accurate w/ high inter-observer variability.

The better question is what's the correct diagnostic pathway to pursue in the setting of pregnancy. In a low prob patient, you could roll the dice and get a D-dimer, knowing that its frequently elevated in normal pregnancy (there are corrected tables out there, but I doubt they're all that accurate). What next? Well, you should probably get a CXR to exclude other causes of tachypnea/hypoxia (ie pneumonia). Then you could go for a bilateral LE ultrasound looking for a DVT (if this is positive go ahead and treat, if negative continue down pathway).

After that, it becomes tricky--CTPA vs V/Q. Issue here is radiation, of course. V/Q has lower total dose (much lower), but slightly higher dose delivered to fetus. CT has higher overall, w/ most delivered to mom's titties, but, with appropriate shielding, lower to baby. It also has the benefit of less diagnostic uncertainty, hopefully preventing another study unlike VQ which is freq. non-diagnostic.

I think most people would opt for the CT, but it's controversial.

For your second question, keep in mind that this is for patients who are actually high risk. Tachycardia and pleuritic chest pain doesn't cut it. We're looking to get a Wells' score of 5 or higher--that's a patient w/ active cancer, hemoptysis, tachycardia and recent surgery. But yeah, in that case you start a heparin drip on the way to CT.

 

[Raryn]

Unlikely that you'll be asked this on the actual test but... The protocol turkeyjerky mentions above is not exactly right. The actual guidelines endorsed by the thoracic people and OGIG are this:

If suspicious of a PE, get a lower extremity ultrasound first. (no radiation) If you see DVT, just treat. If no DVT (likely, even if pt has a PE), get a chest x-ray.

If the chest x-ray is stone cold normal, get a V/Q scan (which actually has quite a bit *less* radiation than a CT). If the V/Q scan is high probability, treat. If low, don't treat. If intermediate, move to CT.

If there are *any* abnormalities on chest x-ray (including things like atelectasis) or if there is an indeterminate V/Q, get a spiral CT of the chest (w/ contrast). If positive, treat. If negative, don't treat.

You never do an angiogram, simply because they have the most radiation of any of the options (yes, a fair bit more than CT) and they have a 2% risk of mortality (5% risk of morbidity).

Never get a d-dimer because it's absolutely worthless in this population. Pregnancy can cause an elevated d-dimer. And false negatives are too risky.

P.S. If you clinically think the patient's symptoms are best explained by PE, that already gives the pt a Wells score of 3. Any other risk factor (tachycardia, immobilization, recent surgery, hx of dvt or PE, hemoptysis, or cancer) put's the pt above the 4.0 threshold to be considered "high risk"

 

[Rollo]

Unlikely that you'll be asked this on the actual test but... The protocol turkeyjerky mentions above is not exactly right. The actual guidelines endorsed by the thoracic people and OGIG are this:

If suspicious of a PE, get a lower extremity ultrasound first. (no radiation) If you see DVT, just treat. If no DVT (likely, even if pt has a PE), get a chest x-ray.

If the chest x-ray is stone cold normal, get a V/Q scan (which actually has quite a bit *less* radiation than a CT). If the V/Q scan is high probability, treat. If low, don't treat. If intermediate, move to CT.

If there are *any* abnormalities on chest x-ray (including things like atelectasis) or if there is an indeterminate V/Q, get a spiral CT of the chest (w/ contrast). If positive, treat. If negative, don't treat.

You never do an angiogram, simply because they have the most radiation of any of the options (yes, a fair bit more than CT) and they have a 2% risk of mortality (5% risk of morbidity).

Never get a d-dimer because it's absolutely worthless in this population. Pregnancy can cause an elevated d-dimer. And false negatives are too risky.

P.S. If you clinically think the patient's symptoms are best explained by PE, that already gives the pt a Wells score of 3. Any other risk factor (tachycardia, immobilization, recent surgery, hx of dvt or PE, hemoptysis, or cancer) put's the pt above the 4.0 threshold to be considered "high risk"

This is correct.

Link:
http://www.thoracic.org/statements/...suspected-pulmonary-embolism-in-pregnancy.pdf