Impact of incident myocardial infarction on the risk of venous thromboembolism: The Tromsø 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 = 29 506) were recruited from three surveys of the Tromsø 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 15.7 years, 1853 participants experienced an MI and 699 experienced a VTE. MI was associated with a 51% increased risk of VTE (HR 1.51; 95% confidence interval [CI] 1.08–2.10) and a 72% increased risk of pulmonary embolism (PE) (HR 1.72; 95% CI 1.07–2.75), but not significantly associated with the risk of deep vein thrombosis (DVT) (HR 1.36; 95% CI 0.86–2.15). The highest risk estimates for PE were observed during the first 6 months after the MI (HR 8.49; 95% CI 4.00–18.77). 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.