Association of unilateral low ankle-brachial index and bilateral low ankle-brachial index with incident cardiovascular disease and mortality: The Northern Shanghai Study

Objective: Ankle-brachial index (ABI) has been used as a marker for atherosclerosis and a risk factor of cardiovascular disease (CVD). Nevertheless, it is not yet clear whether there is a difference in cardiovascular risk between patients with one leg low ABI (<0.9) (unilateral low ABI) and those with both legs low ABI (bilateral low ABI). Therefore, we investigated the association of target organ damage (TOD) and incident of major cardiovascular events (MACE) in participants with unilateral low ABI and bilateral low ABI. Design and method: We enrolled 3168 participants (mean age 71.3 years, 1361 men) from North Shanghai Study (NCT02368938). The participants were divided into 3 groups according to both legs ABI (bilateral low ABI, unilateral low ABI and bilateral normal ABI). TOD, including left ventricular hypertrophy, arterial stiffness, carotid plaque, and renal damage, were measured using standard methods at baseline. MACE was a composite outcome that consisted of nonfatal myocardial infarction, nonfatal stroke and CVD death. Results: Compared with bilateral normal ABI, bilateral low ABI had higher risk of all TOD, but unilateral low ABI only had higher risk of carotid plaque and renal damage after adjustment covariates. During a median follow-up of 5.4 years, 199 MACE and 192 all-cause mortality occurred. The multivariable-adjusted risk for MACE in individuals with bilateral low ABI (hazard ratio (HR): 1.86; 95% confidence interval (CI), 1.20-2.88) and individuals with unilateral low ABI (HR: 1.58; 95% CI, 1.04-2.41) were higher than individuals with bilateral normal ABI (referent group). Compared with bilateral normal ABI, both unilateral low ABI (hazard ratio: 1.70; 95% CI, 1.13-2.57) and bilateral low ABI (HR: 2.10; 95% CI, 1.39-3.18) had higher risk of all-cause mortality after adjustment covariates. Conclusions: Both unilateral low ABI and bilateral low ABI are associated with increased CVD risk, but bilateral low ABI with a trend towards increasing CVD risk. More attention should be paid to whether a patient has a unilateral or bilateral low ABI for a more accurate CVD risk assessment.