Lisa Moores, MD: Challenges in Diagnosing VTE During Pregnancy

Diagnosing VTE in pregnant patients is a huge challenge - both because the patient population is understudied, and common symptoms of the condition are normal during pregnancy. Lisa Moores, MD, sat with MD Magazine at the 2017 annual CHEST Meeting in Toronto, Ontario, to share new approaches for diagnosing VTE in pregnancy.

Lisa Moores, MD, FCCP:

The most frustrating thing for me when you talk about venous thromboembolism in pregnancy is how difficult it is to diagnose it sometimes, and how difficult it is to sort of follow evidence-based guidelines, because we don't have a lot of studies, of course, in pregnant women.

There are guidelines out there. There are American guidelines, Canadian guidelines, European guidelines. They all vary a little bit in what they recommend, so it can be really confusing. If you are someone that likes to look to a big professional society, or an organization for guidance, you're going to get varying recommendations. And so you can imagine that if big societies can't even agree necessarily in each area, you're probably going to get differing opinions from either regional or local experts in your area as well.

The biggest thing, as I said, is that these patients are not included in our randomized trials. And I think it's easy to understand why. But then when you look at standard or traditional diagnostic algorithms, can we apply them to the pregnant patient? We really base everything we do in terms of the diagnostic workup on that initial pretest probability. It's not different than any other disease state, but if you want to interpret each test, and how likely it is that the disease is present in each of those points, then you need to start somewhere. What is that starting prevalence?

We don't have a good standardized prediction rule in pregnant patients. And we have several that are out there that have been well studied. They've been validated populations, particularly the Canadian or the wells room for both DVT and PE have been looked at in both inpatients and outpatients. wWe know those work well, but if you are to tease out the trials where they were either derived or validated, the number of pregnant patients is extremely small. The reason it's difficult is that a lot of the things — the signs and symptoms – that have been found to be useful in those scores are normally present in pregnant patients, just with how their physiology changes.

Most of them are short of breath most of the time. Most of them do get lower extremities swelling, and sometimes that can be asymmetric depending on how the baby is sitting. It's really trying to tease out if this is something that's been there all along, and sort of grounded, or is it something that's acute and even, that isn't necessarily going to be all that accurate.

You have to use your own clinical judgment, and if you don't see a lot of these patients, that can be a little bit difficult. So ultimately, I think we come down to saying, “Well, we know they're at risk, and if there's any possibly in the back of our minds, we should probably look for it. We should probably make sure it's not present.

And then you run into the question of putting the mom and the baby at risk because of radiation exposure. And there are different tests that we have there in in terms of the degree of radiation that the mom feels, and the degree that the baby feels. I think people are somewhat shy of ordering them for that reason.

If I were to give you any take-home point, it would be that the degree of radiation that either the mom or baby feels is still well below what is considered safe, particularly if you’re only going to do one test, and not a series of them. It's much more detrimental to the baby to miss the pulmonary embolisms, and certainly much more detrimental to the mom. So if you're really concerned about it, you should get a test. Use one that you think is going to reliably either confirm or exclude that. CT pulmonary angiogram is going to do that for you most of the time.