Discordant values in lower extremity physiologic studies predict increased cardiovascular risk

BACKGROUND: Ankle-brachial indexes (ABI) are a noninvasive diagnostic tool for peripheral arterial disease and a marker of increased cardiovascular risk. ABI is calculated using the highest systolic blood pressure of the 4 ankle arteries (bilateral dorsalis pedis and posterior tibial). Accordingly, patients may be assigned a normal ABI when the result would be abnormal if calculated using one of the other blood pressure readings. Cardiovascular outcomes for patients with discordant ABIs are undescribed. METHODS AND RESULTS: We performed a retrospective study of patients who underwent ABI measurement for any indication between January 1996 and June 2018. Those with normal ABIs (1.00–1.39) were included. We compared patients with all 4 normal ABIs (calculated using all 4 ankle arteries; n=15 577, median age 64.0 years, 54.4% men) to those with discordant ABIs (at least 1 abnormal ABI ≤0.99; n=2095, median age 66.0 years, 47.8% men). The outcomes assessed were ischemic stroke, myocardial infarction, and all-cause mortality. Compared with patients with concordant normal ABIs, patients with discordant ABIs were older; women; smoked; and had chronic kidney disease, coronary artery disease, diabetes mellitus, chronic obstructive pulmonary disease, hypertension, or prior stroke. Patients with discordant ABIs had a greater risk of myocardial infarction (hazard ratio [HR], 1.31; 95% CI, 1.10–1.56), ischemic stroke (HR, 1.53; 95% CI, 1.37–1.72), and all-cause mortality (HR, 1.27; 95% CI, 1.16–1.39), including after adjustment for baseline comorbidities. CONCLUSIONS: Discordant ABI results were associated with an increased risk of myocardial infarction, stroke, and all-cause mortality in the studied population. Clinicians should examine ABI calculations using all 4 ankle arteries to better characterize a patient’s cardiovascular risk.