EXERCISE IN PATIENTS WITH A NORMAL ANKLE-BRACHIAL INDEX AND AN ABNORMAL TOE-BRACHIAL INDEX UNMASKS LATENT PAD
Author Block DW Armstrong, C Tobin, D Brouillard, MF Matangi
BACKGROUND: In our database, CARDIOfileTM, 76% of 1,258 patients with normal ABIs also have normal toe-brachial indexes (TBI) of ≥0.72, leaving 24% of patients where the TBIs are abnormal. Our purpose was to determine if this latter group of patients may have latent PAD.
METHODS: A normal patient was defined as, an ABI ≥0.95 and ≤1.30 in both legs, no symptoms of claudication, absence of femoral bruits bilaterally and a TBI ≥0.72 bilaterally. A potentially abnormal patient was defined as an ABI ≥0.95 and ≤1.30 in both legs but with an abnormal TBI in either both legs, the R) leg, or the L) leg. We exercised these two groups of patients. Following exercise the brachial systolic pressure in the arm with the highest resting pressure was re-measured followed by the ankle pressures. This sequence was continued for a total of 5 post exercise measurements.
RESULTS: There were 29 patients in the normal group (males =24, females =5), mean age, 60.9 ± 10.5 years. For their 58 legs, the mean resting ABI was 1.16 ± 0.07 and the mean resting TBI was 0.91 ± 0.11. These normal patients had an initial drop in ABI to 1.08 ± 0.11 but by the second measurement this had become non-significant at 1.13 ± 0.11 and by the fourth measurement had returned to baseline at 1.16 ± 0.10. Twenty-six of 29 patients (89.7%) had all normal post exercise ABIs (≥0.95 and ≤1.30). There were 61 patients in the abnormal group (males =36, females =25), mean age, 65.6 ± 9.2 years (P=0.03 compared to normal group). In the patients with abnormal TBIs the mean resting ABI was 1.08 ± 0.08 and the mean resting TBI was 0.64 ± 0.12 for both legs. In the abnormal patients there was a significant drop in mean ABI to 0.91 ± 0.17 post exercise which did not return to baseline. Forty-three of 61 patients (70.5%) had an abnormal fall in ABI post exercise (<0.95).
CONCLUSION: With exercise testing, 89.7% of patients with a normal ABI and TBI have a normal post-exercise ABIs. More importantly, 70.5% of patients with a normal ABI and abnormal TBI have an abnormal post-exercise ABI. Simply measuring the ABI is insufficient to exclude PAD and the TBI should also be measured if the technology is available. If either TBI is abnormal these patients should be exercised in order to identify patients with latent PAD.