The Resistance Index Used to Evaluate Plantar Arch Anatomy in Patients with Chronic Limb-Threatening Ischemia.

BACKGROUND: Evaluation of the anatomy of the plantar arch (PA) is critical to the lower limb (LL) arterial revascularization. PA visualization in severely ill patients is often inadequate, even with digital subtraction angiography (DSA). Considering this, it is important to know if the resistance index (RI) obtained by Doppler ultrasonography (DU) is useful to evaluate the PA anatomy.

OBJECTIVE: To evaluate whether the RI of the distal-leg arteries correlates with the angiographic anatomy of the PA in patients with LL peripheral arterial disease.

METHODS: The study population consisted of 120 patients with critical limb ischemia, admitted for revascularization surgery at the Vascular Surgery Department of HC/EBSERH-UFPE between September 2019 and April 2022. The study design was cross-sectional. DU and DSA were performed on all patients. The RI was obtained via DU and calculated in a given tibial artery by the formula of (peak systolic velocity (PSV)-end-diastolic velocity)/PSV at a segment of artery which in line-flow across the ankle was present distally. The RI was compared with the angiographic anatomy of the PA using the Global Limb Anatomic Staging System classification. The Kolmogorov-Smirnov normality test showed that the sample followed a normal distribution. The Student's t-test was used to compare the types of PA and RI.

RESULTS: A statistically significant difference in the RI was observed in the anterior tibial artery (mean RI 0.48 for complete PA and 0.64; P = 0.018), fibular artery (mean RI 0.47 for complete PA and 0.70; P = 0.047), and dorsalis pedis artery (mean RI 0.42 for complete PA and 0.63; P = 0.008). No statistical significance was found when evaluating the posterior tibial artery (mean RI 0.53 for complete PA and 0.69; P = 0.111).

CONCLUSION: When evaluating tibial arteries which are both reconstituted via collaterals distal to a proximal occlusion and also have runoff onto the foot, lower resistive index corresponds to higher rates of PA patency. Therefore, in reconstituted tibial arteries with adequate runoff to the foot, a greater gap between the PSV and end diastolic velocity correlates to worse pedal compliance and runoff. The RI values obtained for the leg arteries was correlated with complete or incomplete PA anatomy visualized through DSA, thereby contributing to evaluate the distal arterial bed for revascularization surgery.