|Year : 2018 | Volume
| Issue : 2 | Page : 83-86
The correlation of the society for vascular surgery wound, ischemia, and foot infection threatened limb classification with amputation risk and major clinical outcomes
Jessica M Mayor, Joseph L Mills
Michael E. DeBakey Department of Surgery, Division of Vascular Surgery and Endovascular Therapy, Baylor College of Medicine, Houston, TX, USA
|Date of Web Publication||3-May-2018|
Dr. Joseph L Mills
Michael E. DeBakey Department of Surgery, Division of Vascular Surgery and Endovascular Therapy, Baylor College of Medicine, Houston, TX
Source of Support: None, Conflict of Interest: None
The Society for Vascular Surgery Wound, Ischemia, and foot Infection (WIfI) threatened limb classification more comprehensively describes the extent of limb threat in patients with chronic limb-threatening ischemia than many previous classification systems. Several centers have published 1-year amputation rates stratified by WIfI clinical stage. Stage 1 limbs have the lowest amputation risk, Stage 4 limbs have the highest, and Stages 2 and 3 have an intermediate risk. As WIfI clinical stage increases, wound healing time is longer, 1-year wound healing rate is lower, and reintervention rate, hospital costs, length of stay, and readmission rate all increase.
Keywords: Amputation, chronic limb-threatening ischemia, diabetic foot ulcer, peripheral artery disease, revascularization
|How to cite this article:|
Mayor JM, Mills JL. The correlation of the society for vascular surgery wound, ischemia, and foot infection threatened limb classification with amputation risk and major clinical outcomes. Indian J Vasc Endovasc Surg 2018;5:83-6
|How to cite this URL:|
Mayor JM, Mills JL. The correlation of the society for vascular surgery wound, ischemia, and foot infection threatened limb classification with amputation risk and major clinical outcomes. Indian J Vasc Endovasc Surg [serial online] 2018 [cited 2021 Dec 8];5:83-6. Available from: https://www.indjvascsurg.org/text.asp?2018/5/2/83/231845
| Introduction|| |
In 2014, in response to changing patient demographics and increased treatment options for chronic limb-threatening ischemia (CLTI), the Society for Vascular Surgery (SVS) Lower Extremity Guidelines Committee developed a new classification system for threatened limbs based on a thorough literature review and a Delphi consensus process. The SVS Wound, Ischemia, and foot Infection (WIfI) classification system was intended to be applicable across the entire spectrum of patients with CLTI and to aid in patient stratification according to initial disease burden in the affected limb. As patients with threatened limbs are more diverse than in the past, WIfI more completely describes the extent of limb threat than previously utilized classification systems such as those of Rutherford and Fontaine. In addition, WIfI is easy to use and has been incorporated into a free application provided by the SVS.
Calculating WIfI clinical stage is simple. The wound score depends on the extent of the wound and what level of amputation or debridement is predicted to be necessary for limb salvage. All patients require noninvasive arterial studies to determine the ischemia score; ankle-brachial index, ankle systolic pressure, or toe pressure (preferred) can be used. The infection score utilizes the Infectious Diseases Society of America classification system, which does not require complex imaging and can be calculated using clinical data. Each one of the three factors is graded and then used to place the limb at risk into a clinical stage that is expected to correlate with amputation risk.
An update on WIfI in 2017 compiled the first seven studies that analyzed limb outcomes based on baseline WIfI classification. In these studies, the WIfI clinical stage correlated with 1-year amputation risk; the median amputation risk for Stage 1 and Stage 4 limbs was 0% and 34%, respectively.,,,,,, In <1 year, an additional 12 studies have been published;,,,,,,,,,,, the 19 studies included 4450 limbs. With the exception of one study that intentionally excluded patients with diabetes, the prevalence of patients with diabetes ranged from 49% to 100%. [Table 1] summarizes the compiled weighted mean 1-year amputation rates by initial WIfI clinical stage (Stage 1: 3.8%, Stage 2: 8.3%, Stage 3: 9.7%, Stage 4: 23.8%);,,,,,,,,, these results are similar to those published in the 2017 update on WIfI. Looking more closely at the amputation rates per stage across studies, Stage 1 limbs are consistently very low risk, Stage 4 limbs are the highest risk, and Stages 2 and 3 are an intermediate risk with some overlap. However, these data were not stratified into revascularized versus nonrevascularized limbs. Additional endpoints listed in [Table 2] that have been evaluated are wound healing time (WHT), and 1-year wound healing rate (WHR); both appear to correlate with WIfI clinical stage.,,,,,,,, As WIfI stage increased, so did WHT (all weighted means, Stage 1: 92.89 days (range 31–112), Stage 1: 94.32 (range 49–133), Stage 3: 141.30 days (range 125–163), Stage 4: 207.88 days (range 111–263)). The WHR decreased with increasing WIfI stage (all weighted means, Stage 1: 92.0%, Stage 2: 69.32%, Stage 3: 62.38%, Stage 4: 44.89%).
|Table 1: Weighted mean amputation rate by Wound, Ischemia, and foot Infection clinical stage|
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|Table 2: Wound healing time and 1-year wound healing rate by Wound, Ischemia, and foot Infection clinical stage|
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Patients treated according to WIfI stage (i.e., revascularization for limbs with medium or high WIfI stage) had a higher limb salvage rate (90% vs. 78%, P < 0.0001) and amputation-free survival (97.2% vs. 68.1%, P < 0.0001) at 1 year when compared to those patients not treated according to WIfI stage.
Patient comorbidities, particularly renal failure, may impact amputation rates and WHT, regardless of WIfI stage. Hoshina et al. compared outcomes in patients with and without end-stage renal disease who underwent distal lower extremity bypass; the amputation-free survival in the hemodialysis (HD) group was significantly worse than in the non-HD group for patients with WIfI clinical Stage 4 limbs. In a study of endovascular therapy for HD patients, amputation-free survival was 46% at 1 year for patients presenting with clinical Stage 4 limbs (Stage 4 vs. Stages 1–3, P = 0.02), and the 1-year WHR was only 42% (P < 0.01). Regardless of whether revascularization was performed by open or endovascular means, dialysis dependence was associated with a 60.2% WHR at 3 years postrevascularization compared to 84.6% in those not on dialysis; the wound free period was also shorter in those on dialysis (612.5 days vs. 807.6 days, P < 0.001).
Few studies utilizing WIfI have compared outcomes after open surgical bypass versus endovascular therapy for CLTI. In one report of patients who underwent infrainguinal revascularization, freedom from major adverse limb events over the follow-up period of >1 year was the highest in patients who underwent bypass with autogenous vein as a conduit (80%) followed by endovascular therapy and bypass with nonautogenous conduit (72% and 47%, respectively, P = 0.025); bypass was also associated with improved limb salvage in WIfI clinical Stage 4 limbs compared to endovascular therapy (95% vs. 68%, P = 0.026). Similarly, another study found that a bypass- first approach was associated with significantly greater amputation-free survival (77% vs. 20%) and freedom from major amputation (87% vs. 25%, P = 0.006) when compared to endovascular therapy in WIfI clinical Stage 4 limbs. In a study from Japan, an endovascular therapy first strategy was found to be a risk factor against wound healing (relative risk [RR] 2.47, P < 0.0001) and when compared to bypass, was associated with longer WHT (194.4 days vs. 106.4 days, P < 0.0001) and shorter wound free period (639.7 days vs. 763.4 days, P = 0.0127). In contrast, another report from the San Francisco limb salvage group did not find a significant difference in the recurrence of symptoms or wounds among those who underwent no intervention (41%), bypass (52%), or endovascular therapy (41%, P = 0.2).
| Other Endpoints Versus Wound, Ischemia, and Foot Infection Stage|| |
Although originally intended to stratify risk of amputation and secondarily the need for revascularization, numerous reports to date have also examined the correlation of SVS WIfI stage with several other important clinical outcomes, including hospital cost, length of stay, readmission rate, and the requirement for reintervention. These data are briefly summarized below.
| Need for Reintervention/repeat Revascularization|| |
The WIfI clinical stage has been associated with the re-intervention rate. Kobayashi et al. evaluated the utility of repeat endovascular interventions for infrapopliteal lesions. Patients requiring a single intervention had higher 1-year wound healing, limb salvage, and amputation-free survival than those requiring two or more interventions; the rate of requirement for re-intervention correlated with WIfI stage (Stage 1: 0%, Stage 2: 28.6%, Stage 3: 34%, Stage 4: 45.7%, P < 0.001). Patients treated according to WIfI stage (i.e., revascularization for limbs with medium or high WIfI stage) had a higher limb salvage rate (90% vs. 78%, P < 0.0001) and amputation-free survival (97.2% vs. 68.1%, P < 0.0001) at 1 year when compared to those patients not treated according to WIfI stage.
| Hospital Costs, Readmission Rate, and Length of Stay|| |
Increased WIfI stage has been associated with increased healthcare costs. In an analysis of consecutive patients admitted with CLTI, Ramanan et al. found mean direct costs per limb and per salvaged limb were higher for patients with WIfI Stage 4 limbs at all time periods studied (P < 0.05 for both). At 1 year, the mean direct costs per limb were $35,231 for Stage 1 limbs versus $68,258 for Stage 4 limbs; interestingly, in this sample, Stage 3 limbs were less expensive to treat than Stage 2 limbs at 1 year ($29,736 vs. $45,818). Age <80 years was predictive of increased index hospitalization cost (RR 9.1, 95% confidence interval [CI] 1.07–77.4), and Stage 4 limbs were predictive of higher costs at 1 year and over the total follow-up period (1 year: Stage 4 vs. Stage 1 RR 10, 95% CI 1.1–100; total follow-up: RR 12.5, 95% CI 1.25–111.1).
Similarly, in an evaluation of patients with diabetic foot ulcer (DFU), overall charges (inpatient and outpatient) were significantly higher for Stage 4 limbs than for Stage 1 limbs ($61,744± $5989 vs. $4653± $1298, P < 0.001). While outpatient nonoperative management had significantly higher total costs for Stage 4 limbs compared to Stage 1 limbs ($843± $91 vs. $334± $37, P < 0.001), these costs were considerably less expensive than inpatient costs. It follows that efforts to maximize the use of outpatient resources could reduce the overall financial burden created by diabetic foot care.
In CLTI patients who underwent infrainguinal bypass, WIfI Stage 4 was associated with increased length of stay and in-hospital costs than lower WIfI stages (P < 0.005 for all). When all patients admitted to a multidisciplinary limb salvage program were compared, cumulative length of stay was longer in patients with Stage 4 limbs; however, the mean number of admissions per patient was similar across WIfI stages., In contrast, when all comers with DFU were evaluated, mean inpatient admissions increased with increasing WIfI stage (Stage 1, 2.07 vs. Stage 4, 3.40, P < 0.001). In this study, there were significantly more total procedures performed (inpatient and outpatient) as WIfI stage increased (Stage 1, 1.13 vs. Stage 4, 3.01, P < 0.001).
WIfI was not intended to be a static, single-use score; as a patient's clinical course evolves, with resolving cellulitis or improved blood flow after revascularization, the threatened limb should be restaged. The infection and wound grade components of WIfI at 1- and 6-months postrevascularization were correlated with amputation-free survival; the authors suggest that WIfI score at restaging may be helpful in determining which patients may need reintervention. Additional data on restaging and at longer postrevascularization intervals are warranted.
With few exceptions, WIfI has been predictive of amputation risk for threatened limbs; however, as it was developed without prospective data, it follows that there is potential for refinement. Stage 1 and Stage 4 limbs are clearly different; however, some studies have revealed an overlap between Stage 2 and 3 limbs with respect to major amputation risk.,,,,,, There may be certain combinations of WIfI scores that behave differently than predicted or the differences in these strata may be muted by revascularization or by inconsistencies in grading. What is unknown is whether the combinations of WIfI scores within each stage need to be adjusted and whether all practitioners grade foot wounds similarly.
Other potential applications of WIfI exist. As higher stage limbs are associated with worse outcomes and increased costs and utilization of health-care resources compared to lower stage limbs, capturing this difference in diagnosis coding for insurance purposes may be of benefit.
As WIfI stratification is being captured in the Vascular Quality Initiative, the Best Endovascular versus Best Surgical Therapy in Patients with Critical Limb Ischemia trial, and the Bypass Versus Angioplasty in Severe Ischaemia Is The Leg trial, further refinements to WIfI can be made over time to increase the validity and accuracy of this clinical tool.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]