DW. Armstrong1, C. Tobin1, D. Brouillard1, M. Matangi1 - (1) Kingston Heart Clinic, Kingston, Canada
Purpose: The current abnormal ankle-brachial index (ABI) of ≤0.90 is based on the correlation between the ABI with the corresponding peripheral angiographic data. An ABI of ≤0.90 has a high sensitivity and specificity for the detection of a proximal stenosis (≥50%) in the corresponding lower limb. This is useful information for a vascular surgeon. However, for clinicians who are now focused on early diagnosis of vascular disease and the implementation of preventative therapies an ABI of ≤0.90 is not an ideal cut-off. The purpose of our investigation was to attempt to define a normal range for the ABI and determine a more clinically relevant cut-off. Methods: Our cardiology database was searched for all PAD patients who underwent exercise testing with measurement of their ABIs in recovery. Our protocol calls for a series of 5 ABI measurements to be recorded as quickly as possible following the completion of exercise. Patients were excluded from analysis for, a history of claudication, abnormal peripheral foot pulses, iliac bruits, femoral bruits, claudication during the exercise protocol or any decrease in ABI <0.95 following exercise. Patients had to complete the exercise protocol of 5 minutes at 2mph and an incline of 12%, without symptoms. The limits for the normal range for the resting ABI were set at ±2SD from the mean ABI. ANOVA was used to assess differences between the mean values. Tukey-Kramer intercomparisons testing was only performed if the p value for ANOVA was <0.05. Results: There were 40 males and 9 females with a mean age of 61.8±13.5 years. Results are seen in Table 1. There was a minor but non-significant fall in the first ABI following exercise. However, the second and in all subsequent measurements the ABI had returned to baseline. Conclusion: The normal range for the ABI as defined for our population is 0.97 to 1.37 on the right and 0.96 to 1.36 on the left. We believe that a cut-off of ≤0.96 should be used as the threshold to suspect the diagnosis of PAD. Those patients with an ABI between 0.90 and 0.96 should undergo measurement of their ABIs following exercise to see if one can unmask evidence of latent PAD.