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 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 had ABIs less-than-or-equal-to 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 less-than-or-equal-to 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 less-than-or-equal-to 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 less-than-or-equal-to 0.3.