THE ANKLE-BRACHIAL INDEX AS A PREDICTOR OF SURVIVAL IN PATIENTS WITH PERIPHERAL VASCULAR-DISEASE

Objective: To determine whether the ankle-brachial index (ABI) predict s survival rates among patients with peripheral vascular disease. Desi gn: A retrospective survival analysis of patients with abnormal ABIs w ho visited the authors' blood-flow laboratory during 1987. The Nationa l Death index was used to ascertain survival status for all patients u p to January 1, 1992. Kaplan-Meier and Cox proportional hazards analys es were used to determine the relationship between increasing lower-ex tremity ischemia, measured by ABI, and survival time. Clinical charact eristics controlled for included age, smoking history, gender, and com orbidities, as well as the presence of lower extremity rest pain, ulce r, or gangrene. Setting: A university hospital blood-flow laboratory. Patients/participants: Four hundred twenty-two patients who had no pri or history of lower-extremity vascular procedures and who had AB[s < 0 .92 in 1987. Results: Cumulative survival probabilities at 52 months' (4.3 years') follow-up were 69% for patients who had ABIs = 0.5-0.91, 62% for patients who had ABIs = 0.31-0.49, and 47% for patients who ha d ABIs less-than-or-equal-to 0.3. In multivariate Cox proportional haz ard analysis, the relative hazard of death was 1.8 (95% confidence int erval = 1.2-2.9, p < 0.01) for the patients who had ABIs less-than-or- equal-to 0.3 compared with the patients who had ABIs 0.5-0.91. Other i ndependent predictors of poorer survival included age >65 years (p < 0 .001); a diagnosis of cancer, renal failure, or chronic lung disease ( p < 0.001); and congestive heart failure (p < 0.04). Conclusion: The A BI is a powerful tool for predicting survival in patients with periphe ral vascular disease. Patients with ABIs less-than-or-equal-to 0.3 hav e significantly poorer survival than do patients with ABIs 0.31-0.91. Further study is needed to determine whether aggressive coronary risk- factor modification, a work-up for undiagnosed coronary or cerebrovasc ular atherosclerotic disease, or aggressive therapy for known atherosc lerosis can improve survival of patients with ABIs less-than-or-equal- to 0.3.