Title : Association of body mass index with PAD severity and heel-toe exercise ABI performance
Abstract:
Background: Peripheral arterial disease (PAD) is a common manifestation of systemic atherosclerosis, and it is associated with increased cardiovascular morbidity and mortality. Resting ankle-brachial index (ABI) testing is often used for PAD screening, but it may inadequately reflect disease severity, particularly for individuals with non-compressible arteries. Although exercise ABI testing provides greater sensitivity for the diagnosis of PAD, treadmill-based protocols are resource-intensive and not universally feasible. Instead, heel-toe maneuvers offer a practical alternative for provocative ABI testing. Body mass index (BMI) has been variably associated with PAD severity, and several studies have suggested an inverse relationship. The relationship between BMI and PAD severity, as well as its impact on the diagnostic performance of heel-toe-based provocative ABI testing, remains unclear.
Methods: We performed a retrospective analysis of 1,014 patients who underwent resting and heel-toe provocative ABI testing, while using lower extremity arterial duplex ultrasounds as the reference standard for PAD diagnosis. PAD severity was defined by duplex ultrasound as moderate (³50% arterial stenosis) and severe (³75% arterial stenosis), and it was assessed for the right and left extremities. BMI was analysed as a continuous variable and compared across stenosis severity categories. The diagnostic performance of heel-toe ABI metrics, including (a) immediate and delayed post-exercise ABI <0.90, (b) ankle pressure drop >30mmHg, and (c) ABI decrease >20%, was evaluated using sensitivity, specific, predictive values, and area under the receiver operating characteristic curve (AUC). Multivariable logistic regression was used to identify independent predictors of ³50% stenosis.
Results: Lower BMI was consistently associated with greater PAD severity. For both limbs, patients with ³50% stenosis had significantly lower mean BMI compared with those with £50% stenosis (right: 28.10 vs. 29.85 kg/m2; left: 27.91 vs. 29.90 kg/m2; p<0.001 for both). This inverse association was observed in severe PAD (³75% stenosis), with progressively lower BMI seen in patients with higher stenosis burden (p£0.004). Heel-toe provocative ABI testing demonstrated improved sensitivity for detecting both moderate and severe PAD compared with resting ABI alone, particularly for immediate and 2-minute post-exercise measurements (AUCs: 0.71-0.76). Importantly, these diagnostic performance characteristics were preserved in patient groups characterized by lower BMI and higher disease severity.
Conclusions: Lower BMI is associated with increased incidence and severity of PAD, which is consistent with an obesity paradox in lower extremity atherosclerotic disease. Heel-toe provocative ABI testing provides improved diagnostic performance compared with resting ABI, and it also reliably detects moderate-to-severe PAD in patients with lower BMI and advanced disease. These findings support the clinical utility of heel-toe ABI as a practical alternative to treadmill-based exercise testing across diverse body habitus and risk profiles.
