Improved prediction of fatal myocardial infarction using the ankle brachial index in addition to conventional risk factors: The Edinburgh Artery Study

Abstract

Background - Prediction of major cardiovascular and cerebrovascular events using conventional risk factor models is limited. Noninvasive measures of subclinical atherosclerosis such as the ankle brachial index (ABI) could improve risk prediction and provide more focused primary prevention strategies. We wished to determine the added value of a low ABI in the prediction of long-term risk of cardiovascular and cerebrovascular events and death. Methods and Results - In 1988, 1592 men and women 55 to 74 years of age were randomly selected from the age-sex registers of 11 general practices in Edinburgh, Scotland, and followed up over a period of 12 years for incident events. After adjustment for age and sex, an ABI ≤0.9 was predictive of an increased risk of fatal myocardial infarction (MI), cardiovascular death, all-cause death, combined fatal and nonfatal MI, and total cardiovascular events. After further adjustment for prevalent cardiovascular disease, diabetes, and conventional risk factors, a low ABI was independently predictive of the risk of fatal MI. Addition of the ABI significantly (P≤0.01) increased the predictive value of the model for fatal MI compared with a model containing risk factors alone. Comparison of areas under receiver operator characteristic curves confirmed that a model including the ABI discriminated marginally better than one without. Conclusions - Addition of the ABI significantly improved prediction of fatal MI over and above that of conventional risk factors. We recommend that the ABI be incorporated into routine cardiovascular screening and that the potential of its inclusion into cardiovascular scoring systems (with a view to improving their accuracy) now be examined.