1. In this prospective cohort study, patients with symptomatic pulmonary embolism (PE) and a patent foramen ovale (PFO) were found to have a significantly increased risk of ischemic stroke compared to those without PFO.
2. The study results support the hypothesis that paradoxical embolism through a PFO is a significant mechanism leading to increased ischemic stroke risk with PE.
Evidence Rating Level: 2 (Good)
Study Rundown: While it is understood that pulmonary embolism (PE) is associated with an increased risk of ischemic stroke, the underlying mechanism of this phenomenon is still unclear. The authors of this study hypothesized that paradoxical embolism through patent foramen ovale (PFO) is a major mechanism of this association. Based on the study results, the authors observed that the frequency of recent ischemic stroke in patients with symptomatic PE was significantly higher in those with a PFO compared to those without a PFO. The main limitation of the study was that a lower frequency of PFO was found in the cohort compared to that reported of general population studies. Furthermore, the authors acknowledged that some patients were excluded from the analysis due to technical issues with contrast TTE. This exclusion could have impacted the risk estimates for recent ischemic stroke.
In-Depth [prospective cohort study]: The authors conducted a prospective cohort study with masked assessment of stroke outcomes based out of four French hospital centers. The study occurred from November 2009 to December 2015 and included a total of 361 consecutive patients with acute symptomatic PE. All of the patients underwent MRI within 7 days of admission in order to identify and confirm the presence of recent ischemic stroke. The participants also underwent contrast transthoracic echocardiography (TTE) to detect the presence or absence of PFO. Of these patients, PFO was detected in 43 patients through the contrast test. The authors found that silent or symptomatic recent ischemic stroke was diagnosed in 7.6% of the total patients. Patients who had a PFO had a significantly higher frequency of stroke compared to the non-PFO group (9 of 42 patients [21.4%] vs. 15 of 273 patients [5.5%], with a difference in proportions of 15.9 percentage points [95% CI, 4.7 to 30.7 percentage points]; relative risk, 3.90 [CI, 1.62 to 8.67]).
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