The ankle-brachial index as a predictor of survival in patients with peripheral vascular disease

Objective: To determine whether the ankle-brachial index (ABI) predicts survival rates among patients with peripheral vascular disease. Design: A retrospective survival analysis of patients with abnormal ABIs who visited the authors' blood-flow laboratory during 1987. The National Death Index was used to ascertain survival status for all patients up to January 1, 1992. Kaplan-Meier and Cox proportional hazards analyses were used to determine the relationship between increasing lower-extremity ischemia, measured by ABI, and survival time. Clinical characteristics controlled for included age, smoking history, gender, and comorbidities, as well as the presence of lower-extremity rest pain, ulcer, or gangrene. Setting: A university hospital blood-flow laboratory. Patients/participants: Four hundred twenty-two patients who had no prior history of lower-extremity vascular procedures and who had ABIs < 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 had ABIs ≤0.3. In multivariate Cox proportional hazard analysis, the relative hazard of death was 1.8 (95% confidence interval =1.2-2.9, p<0.01) for the patients who had ABIs ≤0.3 compared with the patients who had ABIs 0.5-0.91. Other independent 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 ABI is a powerful tool for predicting survival in patients with peripheral vascular disease. Patients with ABIs ≤ 0.3 have 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 cerebrovascular atherosclerotic disease, or aggressive therapy for known atherosclerosis can improve survival of patients with ABIs ≤ 0.3.