(1) Background: Although the ankle-brachial index (ABI) and skin perfusion pressure (SPP) are commonly used to evaluate the peripheral circulation in critical limb ischemia (CLI), they often cannot be performed on sore areas. We investigated the utility of superb microvascular imaging (SMI) for assessing foot perfusion in CLI patients. (2) Methods: We measured the SMI-based vascular index (SMI-VI) at six sites in the foot before and after endovascular treatment (EVT) in 50 patients with CLI who underwent EVT of the superficial femoral artery and compared the results with SPP values and the ABI. (3) Results: SMI visualized foot perfusion in all subjects in accordance with the angiosome, including the toe areas, while the ABI was unmeasurable in three patients on hemodialysis and SPP failed in four patients. SMI-VI values were significantly lower in the CLI group than in controls, and the plantar SMI-VI had the highest diagnostic performance for CLI (sensitivity 88.6%, specificity 95.6%). After EVT, the increase in the SMI-VI was positively correlated with the increase in SPP but not that in the ABI, implying that the SMI-VI reflects foot microcirculation. (4) Conclusions: SMI enables the visualization and quantification of foot microcirculation based on the angiosome. SMI has high utility as a tool for assessing foot perfusion in CLI.

The most important and consulted guidelines dealing with not healing foot ulcers suggest the measurement of the foot perfusion (FP) to exclude the critical limb ischemia (CLI), because of the high risk of limb amputation. But the recommended cut-off values of FP fail to include all the heterogeneity of patients of the real-life with a not healing ulcer. Often these patients are diabetics with a moderate PAD but with a high level of infection. To meet this goal, in 2014, the Society for Vascular Surgery has published the \"Lower Extremity Threatened Limb Classification System: Risk stratification based on Wound, Infection, and foot Ischemia (WIfI).\" This new classification system has changed the criteria of assessment of limb amputation risk, replacing the single cut-off value role with a combination of a spectrum of perfusion values along with graded infection and dimension levels of skin ulcers. The impact of this new classification system was remarkable so to propose the substitution of the CLI definition, with the new Critical limb-threatening ischemia (CLTI), that seems to define the limb amputation risk more realistically.

Patients with critical limb ischemia have nonhealing wounds and/or ischemic rest pain and are at high risk for amputation and mortality. Accurate evaluation of foot perfusion should help avoid unnecessary amputation, guide revascularization strategies, and offer efficient surveillance for patency. Our aim is to review current modalities of assessing foot perfusion in the context of the practical clinical management of patients with critical limb ischemia.

Peripheral arterial disease (PAD) confers an elevated risk of major amputation and delayed wound healing in diabetic patients with foot ulcers. The major international vascular societies recently developed evidence-based guidelines for the assessment and management of patients with chronic limb-threatening ischaemia (CLTI). CLTI represents the cohort of diabetic and non-diabetic patients who have PAD which is of sufficient severity to delay wound healing and increase amputation risk. Diabetic patients with CLTI are more likely to present with tissue loss, infection and have less favourable anatomy for revascularization than those without diabetes. Although diabetes is not consistently reported as a strong independent risk factor for limb loss, major morbidity and mortality in CLTI patients, it is impossible in clinical practice to isolate diabetes from comorbidities, such as end-stage renal disease and coronary artery disease which occur more commonly in diabetic patients. Treatment of CLTI in the diabetic patient is complex and should involve a multi-disciplinary team to optimize outcomes. Clinicians should use an integrated approach to management based on patient risk assessment, an assessment of the severity of the foot pathology and a structured anatomical assessment of arterial disease as suggested by the Global Vascular Guidelines for CLTI.