Risk of pulmonary embolism lower after CVT than DVT
Individuals with cerebral venous thrombosis (CVT) have a lower likelihood of developing a pulmonary embolism compared with those with deep vein thrombosis (DVT), according to a study presented at the recent International Stroke Conference 2017 (ISC 2017) in Houston, Texas.
Individuals with CVT had a lower risk of developing a pulmonary embolism compared with individuals with DVT (adjusted hazard ratio [adjHR], 0.26, 95 percent confidence interval [CI], 0.22–0.31). [Stroke 2017;48:563-567, ISC 2017, abstract WP179]
“Among patients with CVT, the greatest risk for [pulmonary embolism] was during the index [CVT] hospitalization [1.4 percent for CVT vs 6.6 percent for DVT; p<0.001], suggesting that early detection of CVT and timely initiation of anticoagulation may be important,” said the researchers.
At 5 years, the cumulative rate of pulmonary embolism after CVT was 3.4 percent (95 percent CI, 2.9–4.0 percent) compared with 10.9 percent in DVT patients (95 percent CI, 10.8–11.0 percent; p<0.001).
Using data of patients presenting at emergency departments or hospitalized in California (2005–2011), New York (2006–2013), and Florida (2005–2013), researchers of this retrospective cohort study identified 4,754 patients with CVT (mean age, 43.6 years, 73.3 percent female) and 241,276 with DVT (mean age, 62.5 years, 52.9 percent female). Over a mean follow-up period of 3.4 years, 138 and 23,063 individuals with CVT and DVT, respectively, developed a pulmonary embolism.
According to the researchers, the cumulative rate of pulmonary embolism in CVT patients in this study is higher than that of previous studies (ranging from 0.6–1.8 percent) and could be due to differences in follow-up period or case ascertainment. The inclusion of only patients presenting at emergency departments or after hospitalization may also have limited the cohort to individuals with more severe disease compared with previous studies.
The researchers suggested several possible reasons for the lower risk of pulmonary embolism after CVT including a potential difference in underlying prothrombic states between patients with CVT and DVT.
“There may [also] be important pathophysiologic differences between systemic and intracranial venous clot formation that might at least partly underlie our central finding ... Additionally, because cerebral sinuses are smaller in diameter than deep lower extremity veins, thrombi that break off from the original site in patients with CVT may be small and, therefore, less likely to cause [pulmonary embolism],” they said.
The researchers encouraged further study into identifying optimal therapeutic strategies and treatment duration to prevent recurrent venous thromboembolism after CVT, particularly as current guidelines are mostly based on data derived from studies of patients with DVT.