SS15. Using the Society for Vascular Surgery Wound, Ischemia, and Foot Infection (WIfI) Classification as a Tool to Identify Patients Most Likely to Benefit from Revascularization

Abstract

The Society of Vascular Surgery Wound, Ischemia, and foot Infection (WIfI) classification was intended to predict 1-year major lower extremity amputation (LEA) risk without revascularization, and identify which patients with chronic limb-threatening ischemia benefit most from revascularization. We aim to quantify which patients with chronic limb-threatening ischemia most benefit from revascularization by comparing the predicted to observed 1-year LEA risk stratified by WIfI clinical stage. Composite multiinstitutional nested cohort data from centers that previously validated WIfI were retrospectively reviewed. Individual WIfI component grades, corresponding WIfI clinical stages, and the observed LEA rate for each presentation were compiled. K-means cluster analysis was used to compare predicted LEA risk with that observed after revascularization. Multivariable linear regression analysis was performed to quantify which WIfI score component(s) best predicted amputation. Data from 10 centers were collated (2878 limbs at risk; 314 LEAs performed). The subset of patients undergoing revascularization only comprised the study base (1654 limbs; 169 LEAs). Of 64 potential WIfI grade combinations, 12 were never reported and were excluded from the analysis. By original WIfI stages, the observed LEA rate after revascularization was 6.8% stage 1 (8 of 118), 3.8% stage 2 (18 of 468), 6.0% stage 3 (27 of 451), and 18.8% stage 4 (116 of 617; Fig 1). Cluster analysis identified four clusters with the following 1-year LEA rates: cluster 1, 4.4% (46 of 1038); cluster 2, 14.8% (66 of 447); cluster 3, 28.1% (36 of 128); and cluster 4, 51.2% (21 of 41; Fig 2). The between sum of squares/total sum of squares was 93%. Revascularization benefit was greatest in limbs with small or moderate wounds, moderate to severe ischemia, and moderate to severe foot infection (W2 I2 fI3; W1 I3 fI2). Initially WIfI clinical stage 4, these presentations behaved as lower risk cluster 2 after revascularization. Multiple linear regression revealed wound grade most strongly predicted LEA (F-value 17.25; P < .001). Ischemia (F-value 6.51; P = .001) and infection (F-value 5.7; P = .003) were similarly associated with LEA risk. Interaction terms between each component of WIfI score were not significant. WIfI is a promising tool to identify chronic limb-threatening ischemia presentations most likely to benefit from revascularization, and could be used to better inform patients, guide decision making, and risk-adjust quality and outcomes assessments. Wound severity is most strongly associated with LEA risk. Ischemic and infectious grades confer additive, but not synergistic, risk. Future cluster analyses comparing specific WIfI presentations treated with and without revascularization may quantify the benefit of revascularization for a given WIfI presentation and further refine the risk stratification provided by WIfI.Fig 2The Society of Vascular Surgery Wound, Ischemia, and Foot Infection (Wifi) risk of 12-month lower extremity major amputation (LEA) risk after K-means cluster analysis.View Large Image Figure ViewerDownload Hi-res image Download (PPT)