Abstracts

Rationale: The prevalence of venous thromboembolism (VTE) among people with epilepsy and seizure disorders (ESD) has not been clearly established. ESD and associated comorbid conditions, such as obesity, limited mobility, and cardiovascular disease, may increase the risk of VTE. Furthermore, elective admissions for EEG monitoring often do not involve standard VTE prevention measures due to their potentially negative impact on safety during acute seizures. Currently, prevention of VTE is a publicly reported hospital quality measure. Improved understanding of the risk of VTE in people with ESD is necessary to guide practice decisions. This study provides population-based comparative analyses of the risk of VTE among persons with ESD compared to persons with migraine in South Carolina from 2000-2011.Methods: Persons with ESD and migraine were identified from three state-wide data sources: hospital discharge, emergency department, and hospital-based outpatient clinics. ESD was classified as definite for 2 encounters of ICD-9-CM diagnosis codes of 345.x (epilepsy); or probable with a single 345.x code and prior diagnosis of 780.39 (seizure unspecified). Migraine was defined as at least one encounter of ICD-9-CM diagnosis codes of 346.x. VTE was identified by diagnosis codes of 415.1; 451.[1,2,8,9]; 453.[1-5,7-9]; 997.2, V12.51 occurring concurrently or after a diagnosis of ESD or migraine was established for that subject. Presence of ESD comorbidities was determined by presence of their associated ICD codes. Presence of hypercoagulopathy was defined by diagnosis codes of 289.x. Demographic variables include age, insurance status, gender, race, and urban vs. rural location. Log binomial regression modeling was conducted with Poisson distribution adjusting for clinical and demographic characteristics.Results: There were 32,186 and 35,714 unique individuals with definite and probable epilepsy respectively, resulting in a period prevalence rate of 1.57%. There were twice as many cases of migraine as epilepsy (N=138,497). The prevalence of VTE among ESD was 2.7%, and 0.6% among migraine. The relative risk (RR) of VTE among ESD relative to migraine was 1.56 (95% CI=1.42-1.73) and 1.22 (95% CI=1.09-1.38) for definite and probable epilepsy respectively, adjusting for demographic and clinical covariables. The strongest risk was noted between the number of ESD comorbid conditions and VTE (RR range 17.7 for 2 - 88.8 for 7 comorbidities). VTE was more common among adults than children. Hyper-coagulopathies had a RR of 3.30 (95% CI=2.84-3.83). Other demographic variables had minimal relationship with VTE occurrence.Conclusions: VTE is an important clinical outcome that occurs 27 times more commonly in persons with ESD than in the general US population, and carries significant morbidity and mortality. Although the underlying pathophysiological mechanisms are uncertain, specific risk factors may warrant more aggressive preventive measures in individual patients. Further research is warranted.