Ankle-brachial pressure index (ABI) and toe-brachial pressure index (TBI) are used for the detection of peripheral arterial disease. Low ABI is associated with increased risk of myocardial infarction and cardiovascular death (1,2). The validity of TBI in the prediction of cardiovascular events in patients with diabetes has been hardly evaluated.
After an acute coronary syndrome, 81 patients with type 2 diabetes were recruited (2003–2011). Baseline parameters (men 74.1%, age 65.3 ± 9.1 years, diabetes duration 13.4 ± 9.2 years) were collected and ABI and TBI were measured using standard procedures. TBI data were missing for eight patients, and three patients with an ABI ≥1.3 were excluded from the ABI analysis. During follow-up, all major cardiovascular events (new episode of myocardial infarction, ischemic cerebrovascular disease, or peripheral arterial disease) were registered. Adjusted Cox proportional hazards regression models were used to investigate the predictive value on recurrence for low ABI (<0.9), low TBI (<0.6), or low toe blood pressure (BP) (<50 mmHg).
During a mean follow-up of 44.7 ± 27.8 months, 27.1% of the subjects had at least one major cardiovascular event (19.7% ischemic heart disease, 2.5% ischemic stroke, 4.9% vascular foot ulcer, 3.7% acute limb ischemia with revascularization, 1.2% lower-extremity amputation). Baseline characteristics were similar in patients with or without recurrence. Cox proportional hazards analysis (adjusted for sex, age, duration of diabetes, hypertension, dyslipidemia, smoking status, and mean A1C during follow-up) showed that a low TBI (hazard ratio [HR] 2.92 [95% CI 1.04–8.19]; P = 0.041) and a low toe BP (HR 3.83 [95% CI 1.45–10.1]; P = 0.007) were independent predictors of cardiovascular events, whereas ABI was not (Fig. 1).
![Figure 1. Cox multivariate analysis estimates of the probabilities of recurrent cardiovascular events in patients with type 2 diabetes and established ischemic heart disease grouped according to the initial ABI (HR 0.91 [95% CI 0.38–2.17]; P = 0.8282, log-rank test) (A), the initial TBI (HR 2.92 [95% CI 1.04–8.19]; P = 0.0313, log-rank test) (B), and the initial toe BP (HR 3.83 [95% CI 1.45–10.1]; P = 0.0045, log-rank test) (C). CV, cardiovascular.](/view-large/figure/3948208/dc141843f1.jpeg)
Cox multivariate analysis estimates of the probabilities of recurrent cardiovascular events in patients with type 2 diabetes and established ischemic heart disease grouped according to the initial ABI (HR 0.91 [95% CI 0.38–2.17]; P = 0.8282, log-rank test) (A), the initial TBI (HR 2.92 [95% CI 1.04–8.19]; P = 0.0313, log-rank test) (B), and the initial toe BP (HR 3.83 [95% CI 1.45–10.1]; P = 0.0045, log-rank test) (C). CV, cardiovascular.
Cox multivariate analysis estimates of the probabilities of recurrent cardiovascular events in patients with type 2 diabetes and established ischemic heart disease grouped according to the initial ABI (HR 0.91 [95% CI 0.38–2.17]; P = 0.8282, log-rank test) (A), the initial TBI (HR 2.92 [95% CI 1.04–8.19]; P = 0.0313, log-rank test) (B), and the initial toe BP (HR 3.83 [95% CI 1.45–10.1]; P = 0.0045, log-rank test) (C). CV, cardiovascular.
Our study shows that low TBI and low toe BP in patients with type 2 diabetes and established cardiovascular disease decrease the survival-free time for cardiovascular recurrence. Low ABI, a recognized marker of systemic arteriosclerosis (1,2), was not associated with recurrence in our study. In patients with diabetes and severe arteriosclerosis, medial arterial calcification and arterial stiffening, while not altering TBI, may reduce the ability of ABI to predict new events. On the other hand, low TBI may suggest a widespread vascular disease. Even though the sample size and follow-up duration are not comparable to larger studies, the minor role of ABI as a predictor of cardiovascular events is in accordance with our previous studies, where TBI was found to be a predictor of complications in lower extremities and the best method to evaluate peripheral arterial disease in patients with type 2 diabetes (3–5).
Despite the potential biases of this study, TBI and toe BP are shown to be predictors of recurrence of cardiovascular disease in patients with type 2 diabetes and established ischemic heart disease. Further studies would be needed to expand their role as a screening vascular test to all patients with diabetes.
Article Information
Acknowledgments. The authors appreciate the support of all the members of the Division of Diabetes of the Department of Endocrinology at the Hospital Universitario La Paz. The results of this study are part of the doctoral thesis presented in March 2013 by M.M.-F. at the Autonomous University of Madrid.
Duality of Interest. No potential conflicts of interest relevant to this article were reported.
Author Contributions. M.M.-F. designed the study; collected, analyzed, and interpreted data; and wrote and edited the manuscript. L.H. designed the study, analyzed the data, and reviewed the manuscript. L.S.-d.-I. contributed to collecting the data. L.F.P. contributed to the study design and protocol development and interpreted data. All authors read and approved the final manuscript. M.M.-F. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
