July 26, 2016
2 min read

Lower-extremity classification system predicts amputation risk in CLI

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The Society for Vascular Surgery Lower Extremity Guidelines Committee’s new lower-extremity classification system for wound, ischemia and foot infection was effective for prediction of 1-year amputation, wound healing, and reintervention, major amputation or stenosis events in patients with critical limb ischemia treated with infrapopliteal revascularization procedures, researchers reported in the Journal of Vascular Surgery.

Researchers performed a retrospective chart review to identify all patients who underwent infrapopliteal angioplasty for critical limb ischemia (CLI) at the Beth Israel Deaconess Medical Center between 2004 and 2014. During this time, 673 limbs were treated with infrapopliteal endovascular interventions for the following indications: tissue loss (77%), rest pain (13%), stenosis of a previously treated vessel (5%), acute limb ischemia (3%) or claudication (2%). Limbs lacking a grade in any domain of the wound, ischemia and foot infection (WIfI) classification were excluded. The researchers then used the Society for Vascular Surgery (SVS) WIfI classification for 1-year amputation risk to grade the limbs included for analysis.

The SVS WIfI system offers an objective classification for wound healing and limb amputation based on the following three risk factors: extent of wound (size, depth, gangrene status), degree of ischemia, and extent of infection. The three factors are individually graded on a scale of 0 (least severe) to 3 (most severe), and the grades are then combined to arrive at a WIfI clinical stage for predicting limb amputation risk at 1 year. WIfI clinical stages considered to be “very low risk” for limb amputation at 1 year are classified as clinical stage 1, with stage 4 representing high risk.

The researchers stratified the 551 limbs into clinical stages 1 to 4. They also assigned each limb a new WIfI composite score from 0 to 9, which was calculated as the summary of the three individual WIfI components together.

The researchers analyzed the following study outcomes: patient functional capacity; living status; wound healing; major amputation; major adverse limb events; reintervention, major amputation or stenosis (RAS) events; amputation-free survival and mortality.

Eighty-four percent of the 551 classified limbs were treated for tissue loss and 16% were treated for rest pain. In a Cox regression model, the researchers found a correlation between an increase in clinical stage and the rate of major amputation (HR = 1.6; 95% CI, 1.1-2.3). Additional regression models revealed an association between a 1-unit increase in WIfI composite score and incomplete wound healing (HR = 1.2; 95% CI, 1.1-1.4). A 1-unit WIfI increase also was linked to an increase in the prevalence of RAS events (HR = 1.2; 95% CI, 1.1-1.4) and major amputations (HR = 1.4; 95% CI, 1.2-1.8).

Compared with the WIfI clinical stage, the individual WIfI components and the WIfI composite classification, the high risk (WIfI composite, 5-9) was found to be the strongest predictor of incomplete wound healing (HR = 1.5; 95% CI, 1.1-2), major amputation (HR = 2.2; 95% CI, 1.3-3.7), major adverse limb events (HR = 1.7; 95% CI, 1.2-2.4), RAS events (HR = 1.7; 95% CI, 1.2-2.2) and amputation-free survival (HR = 1.3; 95% CI, 1.1-1.8).

“We believe that this study has proven the value and utility of the WIfI classification system and its related components in regard to patients undergoing a tibial angioplasty for CLI,” the researchers wrote. “In conjunction with patient risk factors and comorbidities, clinical incorporation of the WIfI classification system and our novel WIfI composite score may play an important role in selecting the most efficacious therapy for select patients.” – by Jennifer Byrne

Disclosure: One researcher reports serving on the data entry monitoring board for Endologix Inc. Another researcher reports consulting for Endologix Inc.