Impact of incident myocardial infarction on the risk of venous thromboembolism: the TromsO Study

Background Recent studies have demonstrated an association between venous thromboembolism (VTE) and arterial thrombotic diseases. Objectives To study the association between incident myocardial infarction (MI) and VTE in a prospective population-based cohort. Methods Study participants (n=29506) were recruited from three surveys of the TromsO Study (conducted in 1994-1995, 2001-2002, and 2007-2008) and followed up to 2010. All incident MI and VTE events during follow-up were recorded. Cox regression models with age as the time scale and MI as a time-dependent variable were used to calculate hazard ratios (HRs) of VTE adjusted for sex, body mass index, blood pressure, diabetes mellitus, HDL cholesterol, smoking, physical activity, and education level. Results During a median follow-up of 15.7years, 1853 participants experienced an MI and 699 experienced a VTE. MI was associated with a 51% increased risk of VTE (HR1.51; 95% confidence interval [CI]1.08-2.10) and a 72% increased risk of pulmonary embolism (PE) (HR1.72; 95%CI1.07-2.75), but not significantly associated with the risk of deep vein thrombosis (DVT) (HR1.36; 95%CI0.86-2.15). The highest risk estimates for PE were observed during the first 6months after the MI (HR8.49; 95%CI4.00-18.77). MI explained 6.2% of the PEs in the population (population attributable risk) and 78.5% of the PE risk in MI patients (attributable risk). Conclusions Our findings indicate that MI is associated with a transient increased VTE risk, independently of traditional atherosclerotic risk factors. The risk estimates were particularly high for PE.