Atherosclerosis as a Risk Factor for Venous Thromboembolism (VTE): A Population-Based Cohort Study.

While atherosclerosis has been suggested as a risk factor for VTE, previously identified mechanisms for atherosclerosis and VTE differ dramatically.

Objectives: To compare (a) VTE-free survival and (b) observed vs. expected number of VTE events, among adult patients with and without aortic atherosclerosis.

Design/Setting: Population-based prospective cohort study in Olmsted County, MN.

Patients: Age- and sex-stratified random sample of the adult (≥45 years old) Olmsted County population identified over the three-year period, 1993–1995 (n=573), performed as part of the Stroke Prevention: Assessment of Risk in the Community (SPARC) study.

Measurements: The SPARC study included a baseline clinical evaluation (interviews, review of medical records), blood pressure measurements, blood sampling, and transesophageal echocardiography (TEE). The Risk Factors for VTE in the Community study identified all incident VTE among Olmsted County residents over the 32-year period, 1966–1997, from which expected VTE events by age and sex were calculated.

Results: Over 2830 person-years of follow-up, 12 SPARC patients developed VTE (7 idiopathic). The 4-year VTE-free survival was 99% and 98% for those with and those without any TEE-detected aortic atherosclerosis. Adjusting for age in a Cox proportional hazards model, lack of aortic atherosclerosis was significantly associated with subsequent VTE (p=0.01). Among the 276 patients without atherosclerosis observed for 1423 person-years, 7 VTE were observed compared to 2.6 expected (RR=2.7, 95%CI: 1.1, 5.6). Among the 291 patients with atherosclerosis (plaque ≥2mm), 4 VTE were observed compared to 5.8 expected (RR=0.7, 95%CI: 0.2, 1.8).

Conclusions: Atherosclerosis is not a risk factor for incident VTE.