Resting and postexercise ankle-brachial index (ABI) are independent predictors of mortality, according to the results of a prospective cohort study reported in the March 13 issue of the Archives of Internal Medicine. Even in patients with normal resting ABI, a reduction in postexercise ABI over baseline predicts risk.

"The identification of patients with suspected peripheral arterial disease (PAD) who are at increased risk for cardiovascular events is necessary for disease control and appropriate application of treatment strategies," write Harm H. H. Feringa, MD, from the Erasmus Medical Centre in Rotterdam, the Netherlands, and colleagues. "The ABI, a ratio of ankle systolic–brachial systolic blood pressure, is a simple, effective, and noninvasive test used for the assessment of lower extremity arterial obstruction and for the screening of patients with suspected PAD.... The ABI is commonly measured at rest, but ABI measurements coupled with exercise testing may enhance the sensitivity of the test and may identify additional patients with PAD who have normal resting ABI values."

The investigators measured resting and postexercise ABI values and calculated reduction in postexercise ABI over baseline readings at rest in 3209 patients. Mean age was 63 ± 12 years; 71.1% were male; and mean follow-up was 8 years (interquartile range, 4 - 11 years).

Mortality rate during follow-up was 41.2% (1321 patients). After adjustment for clinical risk factors, significant predictors of mortality were lower resting ABI values (hazard ratio [HR] per 0.10 lower ABI, 1.08; 95% confidence interval [CI], 1.06 - 1.10), lower postexercise ABI values (HR per 0.10 lower ABI, 1.09; 95% CI, 1.08 - 1.11), and higher reductions of ABI values over baseline readings (HR per 10% lower ABI, 1.12; 95% CI, 1.09 - 1.14).

In 789 patients with normal resting ABI, a decrease in postexercise ABI by 6% to 24%, 25% to 55%, and greater than 55% was associated with increased risk for mortality of 1.6-fold (95% CI, 1.2 - 2.2), 3.5-fold (95% CI, 2.4 - 5.0), and 4.8-fold (95% CI, 2.5 - 9.1), respectively.

"Resting and postexercise ABI values are strong and independent predictors of mortality," the authors write. "A reduction of postexercise ABI over baseline readings can identify additional patients (who have normal ABI values at rest) at increased risk of subsequent mortality."

Sanofi-Aventis/BMS, Maassluis/Woerden, the Netherlands, and Lijf en Leven, Rotterdam, supported this study. The authors have disclosed no relevant financial relationships.