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This systematic review suggested that we don't know if treating subsegmental PE harms or helps. But this may inform decision making in patients in whom it would be very dangerous to anticoagulate. It suggests a state of equipoise.
Why does this matter?
With better imaging technology, we are diagnosing PE more often. There is some suggestion that it may lead to anticoagulation of very small, inconsequential emboli--especially given poor interobserver agreement among radiologists. The 2016 CHEST guidelines recommend no anticoagulation for small, subsegmental PE (SSPE) with no proximal DVT and low risk of recurrence. But just how strong are the data behind these recommendations?
Does this make anyone else nervous?
This was a systematic review of 14 studies, with a total of 15,563 patients. There was significant heterogeneity among the studies, and the funnel plot suggested publication bias. Of these, 4.6% (715) had SSPE (<2.5mm arterial diameter). Of those anticoagulated (569 out of 715), 8.1% had a bleeding complication. We don't know the frequency of bleeding in those without anticoagulation. "Bleeding" was poorly defined in most studies and higher than expected compared to other PE research. Risk of recurrence was 5.3% if treated vs 3.9% if not, which was counterintuitive. Mortality was 2.1% if treated vs 3.0% if not, which wasn't statistically different. What we learn from this study is not what we should do in practice. Rather it shows how much we still don't know.
Systematic review and meta-analysis of outcomes of patients with subsegmental pulmonary embolism with and without anticoagulation treatment. Acad Emerg Med. 2018 Mar 2. doi: 10.1111/acem.13399. [Epub ahead of print]
The prolific Brit Long from emDOCS.net has written an incredible post on this subject with 87 references. Anyone that says there is no rigorous scholarship on #FOAMed hasn't seen emDOCs.
Peer reviewed by Thomas Davis.