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The ankle–brachial index (ABI) is used to diagnose peripheral arterial disease (PAD) and to identify those at risk for cardiovascular events. Traditionally, the ABI is calculated using the higher of the dorsalis pedis and posterior tibial ankle arteries. Here we examine whether using the lower of the two ankle pressures identifies additional individuals at increased risk for mortality.
Among 1,413 study participants undergoing coronary angiography, the ABI was calculated using traditional methods and 224 individuals were assigned to the traditional–PAD group (ABI < 0.9). Of those remaining, the alternative ABI method assigned 282 patients to the alternative–PAD group. The 862 individuals remaining were the no–PAD group. Adjusted Cox regression models compared the risk of all–cause and cardiovascular mortality in each group. The C–index assessed the impact of the alternative ABI method on integrated sensitivity and specificity. Among individuals without PAD by either method, the prognostic utility of the brachial–gradient (the left/right brachial systolic pressure difference) was evaluated.
There were 163 mortalities (47 cardiovascular) during a median follow–up of 5.0 years. The alternative–PAD group, who would be classified as not having PAD using traditional ABI methods, had an increased risk for all–cause (HR=1.49; 95% CI, 1.01–2.19) and cardiovascular mortality (HR=3.21; 95% CI, 1.53–6.37) compared to the no–PAD group. The C–index was similar for both ABI methods in predicting all–cause mortality (P=0.150) and significantly greater using the alternative method for cardiovascular mortality (P=0.013). Finally, among individuals without PAD by either method, there was an 11% (HR=1.11; 95% CI, 1.05–1.17) increased risk of all–cause mortality per 1mm Hg increased brachial–gradient.
The implementation of an alternative ABI method identifies individuals at an increased risk for mortality who are currently missed using traditional ABI methods. Additionally, the brachial–gradient, which can be calculated from data already collected during ABI measurement, predicts mortality. Current ABI protocols may need to be evaluated.
Special Session North, Room 120
Monday, March 11, 2013, 11:15 a.m.–11:30 a.m.
Session Title: Young Investigator Awards Competition: Cardiovascular Health Outcomes and Population Genetics
Abstract Category: Cardiovascular Health Outcomes and Population Genetics
Presentation Number: 409–6
- 2013 American College of Cardiology Foundation