Ankle Brachial Index: An Easy and First-Choice Screening Marker of Peripheral Artery Disease and Physical Function

See article vol. 31: 419-428

Peripheral artery disease (PAD) has a largely increasing global prevalence owing to aging population and diabetes pandemic¹⁾. Ankle brachial index (ABI) can be easily and noninvasively measured and is useful for the diagnosis of PAD. The ABI ≤ 0.90 indicates high sensitivity and specificity for the identification of PAD compared with invasive arteriography, which is the gold standard, and ABI ＜1.00 is an appropriate marker to identify patients with an increased risk of coronary events and mortality owing to atherosclerosis^{2, 3)}. In patients with cardiovascular disease (CVD), impaired physical functions reduce physiological reserve and increase vulnerability to adverse outcomes⁴⁾. Therefore, to predict the development of cardiovascular events, physical activities should be monitored. However, physical activity assessment according to the Minnesota Leisure Time Physical Activity Questionnaire is time consuming and may not be suitable for daily routine assessment, especially in patients with old age and reduced cognitive function⁴⁾. Uchida et al. suggested that ABI ≤ 1.1 was potentially associated with poor physical function in patients associated with CVD, highlighting that ABI measurement might be a useful screening method to estimate the severity of frailty⁵⁾.

The association between lower ABI and poor physical function may be owing to skeletal muscle atrophy and its fiber type shift associated with reduced blood flow or owing to either excessive vasoconstriction associated with increased sympathetic nerve activity, activation of the renin-angiotensin system due to decreased cardiac function, and decreased vasodilatory capacity due to decreased production of nitric oxide⁵⁾. This association may be explained by common risk factors for poor physical function and atherosclerosis: aging, malnutrition, insulin resistance, physical inactivity, and chronic inflammation⁵⁾. Several population-based studies have indicated that the ratio of symptomatic to asymptomatic PAD is 1:3 and that patients with asymptomatic PAD have poorer physical function than those without PAD^6-8). In addition, Tanaka et al. reported an association between low ABI and impaired walking endurance in HF patients without intermittent claudication⁹⁾.

Uchida et al. demonstrated the association between the low ABI level and poor physical functions, which were measured by 6-min walking distance, gait speed, short physical performance battery and quadriceps isometric strength, in 2982 patients with CVD⁵⁾. Moreover, based on the detailed ABI levels (i.e., five different categories), patients with CVD may develop poor physical function at a higher ABI level than the traditionally used cutoff value for PAD and have a higher risk of cardiovascular events, which is consistent between each physical function test. Although ABI showed no significant associations with either handgrip or quadriceps isometric strength in 271 patients with PAD, lower ABI was associated with poorer performance in physical function tests, and the study included a relatively small number of patients⁸⁾. This study enrolled most patients in previous studies investigating similar themes. In patients with ABI ＜1.1, physical functions increased with increasing ABI, whereas the increase in physical function plateaued when the ABI reached approximately 1.1, suggesting the importance of lifestyle modification including exercise habits to prevent arteriosclerosis, and to prevent decline in physical function, even in patients with ABI 1.00–1.10, which have not been recognized as abnormal values. Assessing ABI with and without symptoms may help in identifying patients at risk of poor physical function at an earlier time and in stratifying the risk of patients with CVD and implementing interventions at an earlier stage⁵⁾.

Conflicts of Interest

None.

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