Study Shows Prognostic Benefits of Postexercise ABI for Lower Extremity Revascularization

August 17, 2015—In a study published in the Journal of the American College of Cardiology (JACC): Cardiovascular Interventions, Tarek A. Hammad, MD, et al concluded that postexercise ankle-brachial index (ABI) appears to offer both clinical (lower extremity revascularization) and prognostic information in patients with normal and abnormal resting ABIs (2015;8:1238–1244). The investigators, who are with the Cleveland Clinic in Cleveland, Ohio, were led by Mehdi Shishehbor, MD. 

Dr. Shishebor commented to Endovascular Today, “The American College of Cardiology/American Heart Association (ACC/AHA) recommendations typically use resting ABI as the gold standard, but peripheral artery disease patients have exercise-induced symptoms (claudication), so using a postexercise test may be more representative of the perfusion to the lower leg when symptoms are present—and possibly lead to better treatment decisions. A lot of people who may benefit from revascularization may be missed because of the resting ABI test alone. Our study showed that the presence of abnormal postexercise ABI increases the likelihood of lower extremity revascularization by seven times among those who were shown to have normal resting ABI and two times among those with an already abnormal ABI."

As summarized in JACC: Cardiovascular Interventions, the purpose of this study was to investigate the effect of postexercise ABI on the incidence of lower extremity revascularization, cardiovascular outcomes, and all-cause mortality in patients with normal and abnormal resting ABIs. The primary endpoint was the incidence of lower extremity revascularization. Secondary endpoints were major adverse cardiovascular events (MACE) and all-cause mortality. Associations between postexercise ABI and outcomes were adjusted using multivariable Cox proportional hazard and propensity analyses. 

In the study, a total of 2,791 consecutive patients with ABI testing conducted between September 2005 and January 2010 were classified into four groups. Group 1 was composed of patients with normal resting/normal postexercise (NR/NE) ABIs, group 2 patients had normal resting/abnormal postexercise (NR/AE) ABIs, group 3 had abnormal resting/normal postexercise (AR/NE) tests, and group 4 were patients with both abnormal resting and abnormal postexercise (AR/AE) ABI tests. An abnormal postexercise ABI was defined as a drop of > 20% from the resting ABI as per the ACC/AHA guidelines. 

For the groups of patients with normal resting ABIs, the investigators found that group 2 patients with abnormal postexercise ABIs (NR/AE) had increased lower extremity revascularization compared with group 1 (NR/NE), but there were no differences in MACE or all-cause mortality. When the resting ABI was abnormal—group 3 (AR/NE) and group 4 (AR/AE)—an abnormal postexercise ABI was still associated with increased lower extremity revascularization, which persisted after propensity matching. Compared with group 1 (NR/NE), and after propensity matching, group 4 (AR/AE) had a significant increase in MACE and a trend toward increased all-cause mortality, but group 3 (AR/NE) did not, reported the investigators in JACC: Cardiovascular Interventions.