Association Between the Effectiveness and Magnitude of Foot Microcirculation Assessed by Radionuclide Angiography and One Year Limb Outcomes in Patients with Chronic Limb Threatening Ischaemia

Abstract

Objective

Microcirculation focused evaluations may provide physiological insights that complement those of the established clinical criteria for patients with chronic limb threatening ischaemia (CLTI), since complex treatments are needed in this high risk population. However, current methods for quantitatively assessing foot microcirculation are limited. Thus, in this study, the aim was to demonstrate a proof of concept non-invasive method with novel parameters for assessing foot microcirculation.

Methods

This was a single centre prospective cohort pilot study. The lower limbs of 13 patients diagnosed with CLTI were evaluated by radionuclide (RN) angiography with ^99mTc-tetrofosmin two weeks after revascularisation or non-revascularisation procedures. Novel parameters (pedal transit time and peak pedal count) were derived by processing the time–activity curves of the detected tracers in each region of interest in the limbs. The Mann–Whitney U test was used for the analysis of associations between these two parameters and limb fate at one year, and Pearson and Spearman tests were used to analyse associations with transcutaneous partial oxygen pressure (tcPO₂), a conventional perfusion test result.

Results

The mean pedal transit time of the affected limbs in the non-healing group was longer than that in the healing group (19.1 ± 18.6 vs. 2.9 ± 2.1 seconds, p = .001). The mean peak pedal count of nucleotides in the non-healing group was lower than that in the healing group (24.4 ± 19.0 vs. 72.0 ± 36.1 counts/sec/GBq, p = .008). The pedal transit time and peak pedal count showed little to no correlation with the conventional tcPO₂ at the midfoot (r = 0.26 for pedal transit time; r = −0.11 for peak pedal count).

Conclusion

Two novel microcirculation parameters derived from RN angiography were associated with one year limb outcomes in patients with CLTI. Non-invasive radiotracer imaging derived parameters may provide an additional dimension to indices of pathophysiological microcirculation in CLTI.