Decreased Ankle/Brachial Indices in Relation to Morbidity and Mortality in Patients with Peripheral Arterial Disease

Abstract

To determine the relationship between ankle/brachial indices (ABIs) and morbidity and mortality in patients with peripheral arterial disease (PAD), a historical cohort study was performed. A total of 154 patients who had undergone noninvasive arterial assessment of the lower extremities in 1989 and 1990 were selected for this purpose. Selection criteria were age >40 years at the time of investigation, a resting ABI <0.90 and the availability of an ABI after exercise or arterial occlusion. Mortality and vascular events were recorded after an average follow-up period of 6 years. A vascular event was defined as an intervention because of PAD, the occurrence of a nonfatal myocardial infarction or stroke, a transient ischaemic attack or a coronary artery bypass graft (CABG) or percutaneous transluminal coronary angioplasty (PTCA) procedure. During the period studied, 44 patients died and 111 patients suffered a vascular event. The relative risk for mortality was 3.1 per 0.50 decrease of the ABI at rest (95% confidence interval (CI) 1.1–8.7, p = 0.03) and 2.4 per 0.50 decrease of the ABI after exercise or arterial occlusion (95% CI 0.9–6.4, p = 0.08). The relative risk for mortality or the occurrence of a vascular event was 3.3 per 0.50 decrease of the resting ABI (95% CI 1.7–6.3, p<0.001) and 2.5 per 0.50 decrease of the ABI after exercise or occlusion (95% CI 1.5–4.4, p<0.001). After standardization, the prognostic power of the two types of ABIs was equivalent. The cumulative survival after 5 years was 63% for patients with resting ABIs <0.50, 71% for patients with ABIs 0.50–0.69 and 91% for those with ABIs of 0.70–0.89. There were obvious differences between the mean initial ABIs of patients who suffered a vascular event and/or died and those of survivors, who did not suffer an event. A relatively simple measurement like the determination of the resting ABI can give valuable information about the prognosis for vascular related morbidity and mortality. This can be of help in the approach of patients with PAD and assist in therapeutical decision making. Determination of the ABI after exercise or occlusion has no additional value for this purpose.