Importance of peripheral arterial disease as a risk marker in patients with myocardial infarction

The purpose of this thesis was to describe the true prevalence of widespread arterial disease in a cohort with patients with a recent myocardial infarction (MI) to find valuable clinical methods to detect these patients. Our aim was also to investigate biomarker relationships with peripheral artery disease (PAD) and the importance of PAD in patients’ long-term outcomes. We studied patients with a recent MI in a prospective observational study, the REBUS ((Relevance of Biomarkers for Future Risk of Thromboembolic Events in Unselected Post-myocardial Infarction Patients) trial. A total of 421 patients were included in the study, 390 of whom had their ankle-brachial index (ABI) measured and a mean-time follow up of 5.5 years. Atherosclerotic changes were assessed in three arterial beds by coronary angiography, measuring the ABI and carotid ultrasound. Ninety-two biochemical biomarkers were assessed at baseline by a proximity extension assay (PEA) chip. 263 out of 421 filled in a self-administered Walking Impairment Questionnaire (WIQ). Polyvascular (PvD) disease was defined as pathological findings in all three arterial beds. We found that PAD and PvD are underdiagnosed in patients who suffered a recent MI. We also found the ABI to be a strong and useful method to identify patients with PAD as well as patients with more widespread arterial disease, such as PvD (paper I). The results of the scoring system, the WIQ, showed it is useful for finding patients with PAD and PvD, even when completed soon after an acute MI event (paper II). We also found that biochemical biomarkers associated with the inflammatory pathway – tumour necrosis factor receptor 1 (TNFR-1), tumor necrosis factor receptor 2 (TNFR-2) and growth differentiation factor 15 (GDF-15) – were able to predict pathological ABI, i.e. PAD, in these MI patients. These results could also be validated in another observational study and cohort of MI patients, the VaMIS cohort (paper III). Pathological ABI was also found to be a strong predictor for cardiovascular events of all-cause mortality, new ACS, and a composite endpoint of all-cause mortality, new ACS, new stroke/TIA or new PAD event. When evaluating the three inflammatory biomarkers as a surrogate marker for ABI, they showed a similar association with all-cause death and the composite endpoint (paper IV)