Clinical Investigation and Reports Ankle-Arm Index as a Marker of Atherosclerosis in the Cardiovascular Health Study

Background. Peripheral arterial disease measured noninvasively by the ankle-arm index (AAI) is common in older adults, largely asymptomatic, and associated with clinically manifest cardiovascular disease (CVD). The criteria for an abnormal AAI have varied in previous studies. To determine whether there is an inverse dose-response relation between the AAI and clinical CVD, subclinical disease, and risk factors, we examined the relation of the AAI to cardiovascular risk factors, other noninvasive measures of subclinical atheroscle-rosis using carotid ultrasound, echocardiography and electrocardiography, and clinical CVD. Methods and Results. The AAI was measured in 5084 participants 265 years old at the baseline examination of the Cardiovascular Health Study. All subjects had detailed assessment of prevalent CVD, measures of cardiovascular risk factors, and noninvasive measures of disease. Participants were stratified by baseline clinical CVD status and AAI (<0.8, 20.8 to <0.9, 20.9 to <1.0, 21.0 to <1.5). Analyses tested for a dose-response relation of the AAI with clinical CVD, risk factors, and subclinical disease. The cumulative frequency of a low AAI was 7.4 % of participants <0.8, 12.4 % <0.9, and 23.6 % <1.0. Participants with an AAI <0.8 were more than twice as likely as those with an AAI of 1.0 to 1.5 to have a history of myocardial infarction, angina, congestive heart failure, stroke, or transient ischemic attack (all P<.01). In participants free of clinical CVD at baseline, the AAI was inversely related to history o