PAD as a risk factor for mortality among patients with elevated ABI--a clinical study.

OBJECTIVE: This study aims to evaluate mortality across ankle-brachial index (ABI) values and to assess the association between elevated ABI, peripheral arterial disease (PAD) and mortality.

DESIGN: This is a retrospective clinical study.

MATERIAL AND METHODS: A total of 2159 patients referred with a suspicion of PAD had their ABI and toe brachial index (TBI) measured by photoplethysmography. ABI > or =1.3 was considered falsely elevated while TBI <0.60 was the diagnostic criterion for PAD among the subjects. The cohort was followed up for total and cardiovascular mortality until 30 June 2008, by record linkage with the National Causes-of-Death Register.

RESULTS: The average follow-up time was 39 months. A total of 576 (26.7%) patients died during the follow-up. Mortality was highest in the elevated ABI group (35.7% for elevated ABI; 30.1% for low ABI and 16.0% for normal ABI, p < 0.001). There was a greater than twofold risk of total, and an increased but statistically non-significant risk of, cardiovascular mortality among patients with elevated ABI. Similar risk ratios were noted for the low ABI (< or =0.9) group. More pronounced associations were observed at both ends of the scale when ABI was divided into sub-categories. The overall survival was significantly worse for the elevated ABI group than for both the normal and the low-ABI group (p < 0.01 and p = 0.013, respectively). PAD was found to be independently associated with both total and cardiovascular mortality among those with elevated ABI (odds ratio (OR): 2.21; 95% confidence interval (CI): 1.01-4.85 and OR: 4.90; 95% CI: 1.50-16.04, respectively).

CONCLUSIONS: The association between elevated ABI and poor survival is similar to that of low ABI. PAD appears to be an independent risk factor for mortality among patients with elevated ABI.