Ankle-brachial index and cardiovascular outcomes in the Bypass Angioplasty Revascularization Investigation 2 Diabetes trial

Abstract

Background: Peripheral arterial disease increases cardiovascular risk in many patient populations. The risks associated with an abnormal ankle-brachial index (ABI) in patients with type 2 diabetes and stable coronary artery disease have not been well described with respect to thresholds and types of cardiovascular events.

Methods: We examined 2,368 patients in the BARI 2D trial who underwent ABI assessment at baseline. Death and major cardiovascular events (death, myocardial infarction and stroke) during follow-up (average 4.3 years) were assessed across the ABI spectrum and by categorized ABI: low (≤0.90), normal (0.91-1.3), high (>1.3), or noncompressible.

Results: A total of 12,568 person-years were available for mortality analysis. During follow-up, 316 patients died, and 549 had major cardiovascular events. After adjustment for potential confounders, with normal ABI as the referent group, a low ABI conferred an increased risk of death (relative risk [RR] 1.6, CI 1.2-2.2, P = .0005) and major cardiovascular events (RR 1.4, CI 1.1-1.7, P = .004). Patients with a high ABI had similar outcomes as patients with a normal ABI, but risk again increased in patients with a noncompressible ABI with a risk of death (RR 1.9, CI 1.3-2.8, P = .001) and major cardiovascular event (RR 1.5, CI 1.1-2.1, P = .01).

Conclusions: In patients with coronary artery disease and type 2 diabetes, ABI screening and identification of ABI abnormalities including a low ABI (<1.0) or noncompressible artery provide incremental prognostic information.

Figure 1

Kaplan- Meier Event-Free Survival and Major Cardiovascular Event Curves According to Baseline ABI ACM indicated all cause mortality; MI, myocardial infarction; ABI, ankle brachial index; NC, non-compressible. For ACM, compared to normal ABI, p<.0001 for low ABI and NC artery and p=0.34 for high ABI. For ACM/MI/stroke, compared to normal, p<.0001 for low ABI and NC artery and p=0.85 for high ABI.

Figure 2

Relative Risk (RR) of individual outcomes for ABI intervals compared to the interval 1.11 to 1.30 *p<0.05; † RR for stroke was calculated for the ABI interval ‘>1.40’ instead of ‘1.41–1.50’. NC indicates non-compressible; MI, myocardial infarction.