Objective: Subjects with symptomatic peripheral artery disease (PAD) have an elevated prevalence of carotid stenosis and of silent myocardial ischaemia. As such, clinical guidelines advocate the detection of sub-clinical vascular disease in this population. However, the prevalence of occult vascular disease in asymptomatic patients with a low ankle-brachial index (ABI) has not been previously evaluated.
Methods: Cross-sectional study in five primary care centres for patients' selection and two University Hospitals for further assessment. Subjects were 1070 asymptomatic individuals between 60 and 80 years of age with at least two cardiovascular risk factors, selected for ankle-brachial index measurement. Eighty five subjects with an ABI <0.9 and an equal number of controls, matched for age, gender, diabetes, and smoking habit, and with a normal ABI, were referred to the Hospital for carotid ultrasound and exercise stress tests (EST). Main outcome measures were prevalence of a carotid stenosis >50% and an abnormal EST.
Results: The prevalence of a low ABI in the overall population was 9.1%. A carotid stenosis >50% was detected in 14.3% of the subjects with a low ABI and in 4.7% of the control subjects (Odds Ratio [OR]: 3.37; 95% Confidence Interval [CI]: 1.04-10.93, P = .033). The prevalence of a positive EST test was 16.2% in those with a low ABI and 10.5% in control subjects (OR: 1.65; 95% CI: 0.63-4.29, P = .309). These prevalences were higher in older subjects, in those with hypertension or diabetes, or in those with dyslipidemia.
Conclusion: Our results indicate that in high-risk asymptomatic subjects >60 years of age, the presence of an ABI <0.9 identifies a subgroup of the population with an increased prevalence of carotid stenosis and of silent myocardial ischemia and, as such, are candidates for closer follow-up.