The most accepted evaluators of lower limb arterial perfusion are arterial duplex ultrasound (DUS), ankle-brachial indices (ABIs), and toe-brachial indices (TBIs). In patients with diabetes or renal failure, ABI and TBIs can be unreliable due to medial wall calcification. DUS Interrogation of the pedal arterial arch is newly proposed method to measure limb perfusion. A previous study has shown a strong correlation (R2 = 0.88) between the Pedal Acceleration Time (PAT) and ABI in patients with no documented diabetes or renal failure. This study seeks to apply PAT as a predictor of the probability of limb salvage in patients with chronic limb-threatening ischemia (CLTI).