Isolated low toe–brachial index is associated with increased mortality and morbidity: a retrospective cohort study

Objective: The aim was to assess the prognostic impact of perfusion assessments including ankle–brachial Index (ABI) and toe–brachial Index (TBI) on survival of patients who present with diabetic foot ulceration and to analyse clinical outcomes when patients are categorised into three levels of limb ischaemia. Method: This was a retrospective cohort analysis of consecutive patients presenting with foot ulceration. Patients continued with their standard of care, after having baseline assessments of limb perfusion. Patients were retrospectively categorised into three groups according to baseline ABI and TBI: Group 1 (n=31) non-ischaemic (TBI≥0.75, ABI≥0.9), Group 2 (n=67) isolated low TBI with foot ischaemia (TBI<0.75, ABI≥0.90) and Group 3 (n=30) foot–leg ischaemia (TBI<0.75, ABI<0.90). Results: A total of 128 patients took part in the study. Low TBI was associated with a significant decrease in patient survival (42±20 versus 51±16 months, p=0.011). There was a progressive and significant decline in mean patient survival time (51±16 versus 44±20 versus 39±22 months, respectively, for ANOVA across the three groups, p=0.04). Patients with isolated low TBI had angioplasty and bypass at a rate similar to that of patients in Group 3 (low ABI and low TBI). The proportion of angioplasties was significantly higher in the isolated low TBI (19.4% (13/67) versus the non-ischaemic 3.2% (1/31), p=0.033). Such revascularisation resulted in ulcer healing within the foot ischaemic group that was similar to the non-ischaemic group (68% versus 60% over 12 months, p=0.454). Conclusion: Regardless of ABI level, measurement of TBI identifies patients with isolated low TBI who require specialised care pathways and revascularisation to achieve ulcer healing that is similar to non-ischaemic patients.