Testing the sympathetic nervous system of the foot has a high predictive value for early amputation in patients with diabetes with a neuroischemic ulcer

Objective: There is evidence from the literature that dysfunctionality of the sympathetic nervous system of the foot with subsequent loss of local autoregulation could be a predictor of early amputation in patients with diabetes with a neuroischemic ulcer. To confirm this we tested the functionality of the sympathetic nervous system in the foot in a consecutive group of 31 patients with diabetes with critical limb ischemia and non-healing neuroischemic ulcer.

Research design and methods: Prospective cohort with retrospective analysis after 12 months of routinely acquired clinical data. All patients in the study group underwent angiography of the foot as part of a routine angioplasty procedure. Primary study endpoint was lower extremity amputation-free survival at 12 months. Because of the study design no other endpoints could be analyzed. The functionality of the sympathetic nervous system was tested with perfusion angiography.

Results: Thirty-one patients were followed for 12 months. The Capillary Resistance Index (CRI) was used to measure the response of the sympathetic nervous system. CRI≥0.9 is the cut-off point for a non-responsive sympathetic nervous system. All patients (n=11) with a CRI≥0.9 underwent a major amputation before 12 months. Of all patients with a CRI only 15% underwent major amputation. The positive predictive value for major amputation before 12 months for patients with a CRI ≥ 0.9 was 100%.

Conclusions: A non-responsive sympathetic nervous system of the foot is a strong predictor of early major amputation (log rank p<0.001; HR 14.22; 95% CI 3.64 to 55.51).