Wednesday, January 13, 2016

The “Don’t Anticoagulate Pulmonary Embolism” Guideline

We’ve expressed a lot of angst around these parts regarding the homogenous treatment of acute pulmonary embolism.  With the advent of angiography, and then computed tomography with ever-increasing levels of sensitivity, the physiologic spectrum of disease for pulmonary embolism has massively increased.

In olden times, pulmonary embolism actually presented as pulmonary infarction with the “classic” triad of pleuritic pain, hemoptysis, and signs of deep venous thrombosis.  Now, nearly 10% are virtually incidental subsegmental PE of uncertain clinical significance – yet, recommendations for treatment remained systemic anticoagulation.

Until now.

This new guideline states patients with subsegmental PE, without another identifiable VTE source, and at low risk for recurrent VTE, have the option of watchful waiting.  They cite no new groundbreaking evidence, but generally recognize the low rates of recurrent VTE in retrospective and observational studies.  They also recognize a diagnosis of subsegmental PE is quite likely to be a false-positive, as covered in my last ACEPNow column, unless the following conditions are met:
We suggest that a diagnosis of subsegmental PE is more likely to be correct (i.e. a true-positive) if: (1) the CT pulmonary angiogram (CTPA) is of high quality with good opacification of the distal pulmonary arteries; (2) there are multiple intraluminal defects; (3) defects involve more proximal sub-segmental arteries (i.e. are larger); (4) defects are seen on more than one image; (5) defects are surrounded by contrast rather than appearing to be adherent to the pulmonary artery; (6) defects are seen on more than one projection; (7) patients are symptomatic, as opposed to PE being an incidental finding; (8) there is a high clinical pre-test probability for PE; and D-Dimer level is elevated, particularly if the increase is marked and otherwise unexplained.
Patients discharged without anticoagulation should be provided prospective guidance on seeking care for new or progressive symptoms.  These recommendations are appropriately GRADE category 2C, reflecting moderate/weak certainty and a low level of evidence – but, it at least provides a framework to have a reasonable conversation and shared decision-making with a patient.

It also appropriate raises a question about testing for PE:  if a patient has a PE meeting criteria for non-treatment, does it need to be found in the first place?  Should the acceptable miss rate for PE – assuming the quoted prevalence of subsegmental disease – be ~10%?

“Antithrombotic Therapy for VTE Disease: CHEST Guideline”


  1. Well, this raises 2 different questions.

    1- Is the image a clot or not ?

    2- More fundamentally: does a true small clot deserve treatment?

    Once the clot is deemed true I don't see any change in these guidelines for the ED doc.

    I suppose ED patients either have a high clinical probability and directly went to CT angiography, or the probability was lower and D Dimers above (age corrected) threshold , therefore, as per the guidelines they'll be treated as before.

    I don't see a real change except that we should look at the CT on the screen ourselves. But if we disagree with the radiologist , we'll have to over-rule him/her if we don't treat. Tricky .

    Oh I was forgetting the occasional patient getting a Ct for other reasons and found with a small clot hence sent to the ED. But this is'nt a true ED patient.

    The change is not so much for ED practice , it seems.

    1. This mostly raises question 1, and then uses some assumptions about the answer to question 2 to justify how to handle question 1.

      I think this mostly protects patients with the incidental PE – e.g., the patient getting their abdominal CT with an incidental finding of PE in the lower lobes. Unfortunately, the other false positives are probably getting their CTs because the treating clinician erroneously overjudged their pretest likelihood – although, there are probably some other cases in which a "chest pain protocol" sends a D-dimer that comes back mildly elevated and boxes the liability-averse clinician into ordering the CTA. Then again, the liability-averse clinician who inappropriately followed the non-specific D-dimer elevation probably isn't the clinician comfortable with the no-anticoagulation option ....

    2. Most incidental EPs sent by the Roentgen squad to us (a very rare situation actually) are done for cancer diagnosis or staging. A prothrombophiliac situation.This guideine might save some of those patents anticagulation. Unfortunately , patients wth an extended cancer will rarely have normal d dimers.

    3. I don't think this guideline saves anyone anticoagulation who is in a thrombophilic state, with a new PE. It's certainly still a reasonable risk/benefit/QOL conversation to have with someone with cancer whether they're interested in long-term anticoagulation therapy, but definitely not covered in this guideline.


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