Background: Critical limb threatening ischemia (CLTI) is the most advanced stage of lower extremity arterial disease (LEAD) and is associated with an increased risk of amputation and mortality. The main means for CLTI diagnosis is the use of toe pressure (TP). Duplex Ultrasonography (DUS) flow analysis by using the Saint-Bonnet classification could assess arterial impairment, but its relationship with CLTI defined by TP has not been evaluated. The first objective was to assess the relationship between Saint-Bonnet classification at ankle and hemodynamic CLTI, defined by TP ≤ 30 mmHg, and its diagnostic performance. The second objective was to study the correlation between systolic rise time and TP.

Material and methods: This retrospective observational study included patients undergoing lower-limb arterial DUS and TP at the University Hospital Center of Guadeloupe between June 2022 and November 2023. Statistical analyses included univariate and multivariable analyses, diagnostic performance assessment and Pearson correlation.

Results: One hundred and fifty-three patients were included (276 lower limbs). CLTI was significantly associated with 0 and E categories of Saint Bonnet in univariate (p<0.001) and multivariable analysis (p<0.001), with 94% specificity and 65% positive predictive value. N, A or B categories appeared to rule out CLTI, with a 100% negative predictive value in a population at high risk of mediacalcosis. No significant correlation was found between Systolic rise time and toe pressure (p = 0.0773).

Conclusion: Saint Bonnet Classification may help in the diagnosis of CLTI, but these findings need confirmation in a larger prospective diagnostic and prognostic study.