Relationship of a Low Ankle-brachial Index with All-cause Mortality and Cardiovascular Mortality in Chinese Patients with Metabolic Syndrome after a 6-Year Follow-up: A Chinese Prospective Cohort Study

Objective Peripheral arterial disease (PAD) is a common clinical manifestation of the systemic atherosclerotic process, and the ankle-brachial index (ABI) is an ideal tool to diagnose PAD. Currently, there have been few long-term follow-up studies focused on the associations of the ABI with all-cause mortality and cardiovascular disease (CVD) mortality in Chinese MetS patients. The aim of this study was to evaluate the usefulness of ABI to predict the prognosis of CVD in hospitalized Chinese patients with metabolic syndrome (MetS). Methods Participants from multi-center departments were followed up from November 2004 to January 2011. The study sample actually comprised 1,266 valid participants whose age was >= 35 years. Patients were separated into four groups, with an ABI <= 0.4, 0.41-0.7, 0.71-0.9 and 0.91-1.4. An ABI <= 0.9 was defined as PAD, and subjects with an ABI >1.4 were excluded because of the false negative rate. Factors related to all-cause and cardiovascular mortality were observed by Cox models and the log rank test. Potential confounding variables with values of p<0.10 were adjusted for the multivariate analysis. Results An abnormal ABI value was strongly, independently, and inversely correlated with the all-cause and cardiovascular mortality. After adjusting for age and other covariates, Cox models revealed that an abnormal ABI value was still correlated with the all-cause mortality (relative risk/RR/=1.82, 95% confidence interval/CI/=1.45-2.34 p<0.01), and CVD mortality (RR=1.88, 95% CI=1.51-2.90 p<0.01). Conclusion An abnormal ABI value was not only a significant and independent risk factor for CVD, but also for the survival rate in Chinese MetS patients. Routine ABI evaluation could therefore be helpful for identifying high risk patients, especially MetS patients.