ABI derived from the highest and lowest ankle pressure. What is the difference?

AIM

Different modes of ankle-brachial -index (ABI) calculation lead to different information. We looked for the peripheral arterial disease (PAD) prevalence estimated from ABI-high and ABI-low and analysed the effect of age and classical risk factors.

METHODS

Based on the Arteriomobil Project data, ABI was calculated considering the lowest of the four ankle artery pressures (ABI-low) or the higher ankle artery pressure of each leg (ABI-high), respectively. ABI <0.9 were defined to prove PAD.

RESULTS

Prevalence of PAD estimated using ABI-low was much higher than those using ABI- high (15.7% vs. 8.0%). Thus 8% of men and 7.5% of women suspected for PAD were not detected if prevalence rates are based on ABI-high alone. Estimating PAD prevalence only by measuring posterior tibial artery (ATP) pressure, prevalence rates were lowest with 2.4% for the left and 2.7% for the right ATP. Estimating PAD prevalence only by measuring anterior tibial artery pressure, prevalence rates were slightly higher, but still low. ABI-high systematically shows lower prevalence rates compared to ABI-low without divergence of the prevalence rates with increasing age. This parallelism of the curves remained unchanged when prevalence rates were separated for self-reported risk-factors; smoking, hypertension, hypercholesterolemia and diabetes.

CONCLUSION

The presented analysis of the Arteriomobil Project data support the hypothesis that the differences in prevalence rates estimated from ABI-high and ABI-low are mainly determined by anatomic variations of the plantar arch. Additional angiographic controlled studies are necessary to prove this hypothesis.