Plantar Acceleration Time: A Novel Technique to Evaluate Arterial Flow to the Foot

Arterial duplex ultrasound (DUS) and ankle-brachial indices (ABIs) are accepted methods for assessing lower limb arterial perfusion. However, in a significant number of diabetic patients, medial wall calcification often precludes an ABI measurement. Direct, noninvasive duplex imaging of the pedal arch in the setting of peripheral arterial disease (PAD) has not been well evaluated. Although plantar arch interrogation is new to vascular ultrasound, imaging the plantar arteries appears to be a reliable angiographic technique for critical limb ischemia. We sought to define the utility of Plantar Acceleration Time as a surrogate for ABIs.

Patients undergoing DUS including Plantar Acceleration Time for suspicion of PAD were retrospectively reviewed in a prospective database over a 1-year period. Two hundred fifty nondiabetic patients (499 limbs) with documented ABI were studied. Plantar Acceleration Time was calculated (milliseconds [msec]) in each limb in the lateral plantar artery. Statistical analyses were performed using linear regression and analysis of variance testing using Microsoft Excel database (version 2016; Microsoft Corp, Redmond, WA). Patients were then grouped into 4 classes based on their clinical symptoms and ABI. Plantar Acceleration Time was similarly grouped into 4 distinct classes and correlated with the clinical and ABI classes.

Plantar Acceleration Time correlated significantly with ABI (P < 0.001). There were significant differences in Plantar Acceleration Times between each class based on ABI and clinical presentation (P < 0.001 for each): Class 1 Plantar Acceleration Times 89.9 ± 15.5 msec; Class 2, 152.3 ± 28.4 msec; Class 3, 209.8 ± 25.5 msec, and Class 4, 270.2 ± 35.3 msec.

Plantar Acceleration Time demonstrates a high correlation with ABI in patients with compressible arteries. Based on our results we propose the following categories of Plantar Acceleration Time, which appear to correlate with both clinical and ABI findings. ABI of 0.90-1.3 correlates with a Plantar Acceleration Time of 0-120 msec, ABI of 0.69-0.89 correlates with a Plantar Acceleration Time of 121-180 msec, ABI of 0.40-0.68 correlates with a Plantar Acceleration Time of 181-224 msec, and an ABI of 0.00-0.39 correlates with a Plantar Acceleration Time of greater than 225 msec. Further studies are ongoing to confirm whether Plantar Acceleration Time may be a suitable substitute to ABIs in patients with noncompressible arteries that preclude meaningful ABIs and gives more information regarding targeted angiosome perfusion to the foot.