Introduction: Cerebral vein thrombosis (CVT) is associated with an increased risk of subsequent venous thromboembolism. It is unknown whether the risk of pulmonary embolism (PE) after CVT is similar to that of PE after deep venous thrombosis (DVT).
Methods: We performed a retrospective cohort study using administrative claims data from all emergency department visits and hospitalizations in California from 2005-2011, New York from 2006-2013, and Florida from 2005-2013. We identified patients with CVT or DVT as well as the primary outcome of PE using previously validated International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes. In order to minimize misclassification error, patients with both CVT and DVT during the same index hospitalization were excluded and patients with CVT were censored at the time of development of DVT and vice versa. Kaplan-Meier survival statistics and Cox proportional hazards models were used to compare the risk of PE after CVT versus after DVT while adjusting for demographics, vascular risk factors, and the Elixhauser comorbidity index.
Results: We identified 4,450 patients with CVT and 217,589 patients with DVT. During a mean follow-up of 2.0 (±1.7) years, 124 patients with DVT developed a PE and 18,698 patients with DVT developed a PE. Patients with CVT were younger (mean age 45 vs 63), more often female (71% vs 52%), more often pregnant, and had fewer vascular risk factors than patients with DVT. During the index hospitalization, the rate of PE was 1.5% (95% confidence interval [CI], 1.1-1.8%) in patients with CVT and 6.2% (95% CI, 6.1-6.3%, p<0.001) in patients with DVT. By 5 years, the cumulative rate of PE after CVT was 3.7% (95% CI, 3.0-4.4%) compared to 10.5% (95% CI, 10.3-10.6%, p<0.001) after DVT. After adjustment for demographics and comorbidities, CVT was associated with a significantly lower hazard of PE when compared to DVT (hazard ratio, 0.31; 95% CI, 0.26-0.38).
Conclusion: In a large, heterogeneous population, we found that the risk of PE after CVT was significantly lower than that of PE after DVT. Among patients with CVT, the greatest risk for PE was apparent during the index hospitalization.