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Very few patients with syncope have pulmonary emboli
Clinical Question
How often do patients who present with syncope have a pulmonary embolism?
Bottom line
In this meta-analysis, the rate of pulmonary embolism (PE) is less than 2% among patients with syncope, even if you include one influential outlier study. 2a-
Reference
Study design: Meta-analysis (other)
Funding: Self-funded or unfunded
Setting: Other
Synopsis
These authors were surprised at what they perceived to be an extraordinarily high rate of PE among the patients hospitalized for syncope reported by Prandoni and colleagues (N Engl J Med 2016;375:1524-1531). So, they decided to search multiple databases to identify studies of patients who presented to the emergency department, or who were hospitalized, with syncope. They also manually searched the reference lists of included studies. Two of the authors independently assessed the inclusion eligibility of each study, assessed the risk of bias, and extracted the data. A third author "checked their work." They ultimately included 12 studies with 7583 patients. Nine of the studies took place in the emergency department and 3 assessed patients who were hospitalized for syncope. (Curiously, the authors excluded the Prandoni paper, which included 560 patients. Another approach might have been to include that paper and then conduct a sensitivity analysis. After all, isn't that the reason for doing meta-analyses—to look at ALL of the data?) Most of the included studies did not report either how the diagnosis of PE was established or the degree of clinical suspicion for PE. Only 48 patients in the included studies had a PE (0.63%): 39/6608 emergency department patients (0.59%) and 9/975 hospitalized patients (0.92%). If you include the 97 patients with PE from the Prandoni study, the overall rate is 1.8%—still pretty low. Among the plausible reasons for the discordance between the Prandoni study and the rest: formal screening for PE versys relying on clinician gestalt, inconsistent evaluation for PE, older patients, and/or comorbidities. It will take a large, well-designed cohort study to resolve these discrepancies.
Reviewer
Henry C. Barry, MD, MS
Professor
Michigan State University
East Lansing, MI
Comments
good poem
Interesting study. It appears to me that the meta analysis in and by itself has some significant flaws. What would be interesting to know is the rate of PE overall. That may not be possible without a registry of some type. I wonder....
So I "hate" PE. As an EM doc I have seen patients with PE presenting every which way. Whenever I have a sign-over from one of my colleagues who tells me about a patient diagnosed with PE, I read the chart word for word and go speak to the patient directly to try and "discover" whether I would have investigated them for PE. It is not unusual for me to say "there but for the grace...." because I honestly don't think I would have investigated them (and I don't think I am a bad doctor!). Not sure what to say about this article since the review does not lay out what "size" of PE patients have but my sense is that a PE causing syncope must be a big one and I would not want to miss any of the 2% of them, just like I don't want to miss 2% of patients who are having a STEMI. Fortunately there a few really good clinical decision tools out there that help one navigate this morass. I can only say for any syncope patient presenting to the ED be very assiduous about applying your rule of choice. If anything this article supports this notion.