• The concept of a single dichotomous hemodynamic cutoff point for CLI no longer applies to the majority of patients encountered in current clinical practice; various degrees of ischemia may prove "critical" depending on the overall status of the limb.
• It has become clear that limb ischemia does not have sharp cutoff points but consists of a gradual spectrum in the pattern of a sigmoidal curve (Fig).
• The new system we have developed dispenses with the term CLI and instead creates an objective classification of the threatened limb based on the degree of ischemia, wound extent, gangrene, and infection.
• This updated Society for Vascular Surgery (SVS) Lower Extremity Threatened Limb Classification System is intended to define the disease burden, analogous to the tumor, node, metastasis (TNM) system for cancer staging.
• It is not intended or designed to influence or dictate treatment method, especially since treatment modalities continue to evolve.
• The primary purpose of this classification is to provide more precise description of the disease burden to allow accurate outcomes assessments and comparisons between similar groups of patients and alternative therapies.