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Ankle–brachial index (ABI) is conventionally calculated as the ratio of higher of the two systolic ankle blood pressures to the higher brachial systolic pressure (HABI method). Patients with clinical suspicion for peripheral arterial disease (PAD) but normal or mildly abnormal ABI (0.8 to 1.3) by HABI method are referred for exercise ABI test. We hypothesized that an alternate method using the lower of the two systolic ankle pressures (LABI method) would help predict abnormal exercise ABI test.
All patients who underwent resting ABI study and exercise ABI study between July 2008 and December 2011 in our institution were enrolled. Exercise ABI was calculated using standard protocol after 5 minutes of exercise at 2 miles/hour at a gradient of 12%. Subjects with ABI >1.3 were excluded.
A total of 93 patients were enrolled (186 limbs). At rest LABI method detected abnormal ABI (<0.9) in 49% of patients compared to 34% of patients detected by HABI method. Exercise ABI test was abnormal in 31% of these patients. Table shows the changes in diagnostic ability of LABI method using various cut off's to detect abnormal exercise ABI. A rest ABI of <0.8 by LABI method had a specificity of 91% and positive predictive value of 85% to predict an abnormal exercise ABI test.
In patients referred for exercise ABI study, a rest ABI <0.8 by LABI method predicts abnormal results. Further studies are needed to determine if these patients can directly be referred for angiogram and avoid exercise ABI test.
|Abnormal Exercise ABI <0.8||Abnormal Exercise ABI <0.9|
Poster Sessions, Expo North
Monday, March 11, 2013, 9:45 a.m.–10:30 a.m.
Session Title: Markers to Assess Peripheral and Carotid Artery Disease: Rapid Advances
Abstract Category: 35. Vascular Medicine: Non Coronary Arterial Disease
Presentation Number: 1297–163
- 2013 American College of Cardiology Foundation